Anderbrant, O. 1990. Gallery construction and oviposition of the bark beetle ips-typographus coleoptera scolytidae at different breeding densities. Ecol. Entomol. 15 (1). 1-8. ab 1. The bole of a Norway spruce, Picea abies (L.) Karst., was cut in 25 cm sections and infested in the laboratory with 2 or 8 females/dm2 of Ips typographus (L.) and an equal number of males. 2. One log of each beetle density was dissected every second day, beginning 2 days after female introduction. 3. The oviposition rate was highest at the beginning of the breeding period for both densities and then declined, especially at the high density. Residence time is a useful approximation for the number of laid eggs in the beginning of the oviposition period or when the density is low. 4. Final gallery length and egg number per gallery were on average significantly smaller at density 8 than at density 2. 5. Linear relationships between total gallery length and number of egg niches were found to be similar for the two densities. 6. An estimate of the egg to adult mortality at different densities was found by using data from a field study that related gallery length to breeding density in attacked living trees, together with published relationships between density and egg niches or emergence of new adults. 7. It was concluded that both decreased oviposition rate and earlier reemergence at high densities contribute to a declining oviposition with increasing density. The final offspring production is further reduced by lower survival due to larval competition as density increases. LG EN.

Anderbrant, O., Schlyter, F., & Birgersson, G. 1985. Intraspecific competition affecting parents and offspring in the bark beetle ips-typographus. Oikos 45 (1). 89-98. ab In the laboratory we investigated the effect of breeding density on the reemergence of parent spruce bark beetles Ips typographus (L.), and on the number and "quality" of their offspring. The parents reemerged sooner at higher densities but the total proportion that reemerged was independent of density. More than 20 offspring per female were produced at the lowest density (0.5 .female..female./100 cm2) but only 0.6 per female at the highest density (31 .female..female./100 cm2). The offspring from the lowest density were about 50% heavier than those from the highest density and also the fat content (%) increased with decreasing density. Females weighed less and contained less fat than males. Male offspring from lower densities produced larger amounts of the pheromone components cis-verbenol and 2-methyl-3-buten-2-ol than males from the higher densities. Offspring from the highest produced about half as many progeny as those from the lowest densities, showing an effect of density acting over more than one generation. These findings suggest that density-induced variation of beetle "quality" might be of importance in the population dynamics of bark beetles. LG EN.

Bakke, A. 1981. Inhibition of the response in ips-typographus to the aggregation pheromone field evaluation of verbenone and ipsenol. Z. Angew. Entomol. 92 (2). 172-177. ab Field bioassay showed that the aggregation of the spruce bark beetle, I. typographus on traps baited with the attractive synthetic pheromone mixture, was significantly reduced by the addition of verbenone and ipsenol, which act as inhibitors. When both components were added the reduction in trap catches was most significant and the proportion of responding male beetles caught was significantly reduced. It is hypothesized that verbenone released by the boring beetles counteracts the effect of the aggregation pheromone and shifts the attack to uninfested bark areas of the 3 under attack or to neighboring trees. Ipsenol inhibits the response to the aggregation pheromone, but an explanation of the actual biological function of ipsenol depends on the absolute configuration of ipsenol released by I. typographus being established. LG EN.

Birgersson, G., & Bergstrom, G. 1989. Volatiles released from individual spruce bark beetle entrance holes quantitative variations during the first week of attack. J. Chem. Ecol. 15 (10). 2465-2484. ab Volatiles released from individual entrance holes of eight spruce bark beetles (Ips typographus) were collected during the first week of attack on a resistant host tree. In order to quantify the release of the highly volatile 2-methyl-3-buten-2-ol (MB) from attacking males, a new method was developed with deuterated quantification standard released at the time of collection. The amounts of collected volatiles, as analyzed by GC and GC-MS, showed a large variation between individual holes and also between subsequent entrainments from the same hole. Most of the quantified compounds on the average have two maxima, with a pronounced intervening depression. The amounts of released cis-verbenol (cV) increased five times during the first two days, while the amounts of MB were cnsistently high. The attacked spruce tree was not taken by the beetles, and the average amounts of the two aggregation pheromone components. MB and cV, increased again after the first maxima. The first peak of oxygenated monoterpene, released in the beginning of the attack containing .alpha.-terpineol, terpinen-4-ol, bornyl acetate, trans-pinocarveol, and verbenone, was possibly due to spontaneous oxidation of monoterpene hydrocarbons from the tree. Microorganisms established in the gallery wall phloem probably participated in the production of oxygenated monoterpenes during the second increase. LG EN.

Birgersson, G., & Leufven, A. 1988. The influence of host tree response to ips-typographus and fungal attack on production of semiochemicals. Insect. Biochem. 18 (8). 761-770. ab Amount and composition of pinene alcohols in the hindgut of individual Ips typographus males are correlated with those of monoterpenes in the surrounding spruce phloem. The beetle's efficiency in oxidizing difensive host tree monoterpenes declines as the attack on a tree proceeds, and these processes are then probably taken over by fungi in the gallery walls. Linear models can be constructed which use the amounts of host tree produced .alpha.- and .beta.-pinene and fungal produced borneol present in phloem, to estimate the amounts of pinene alcohols in beetle hindguts. The amounts of some oxygenated monoterpenes in the phloem can be correlated with a brown discolouration of the gallery walls, interpreted as a sign of fungal establishment. The beetle's production of the aggregation pheromone component 2-methyl-3-buten-2-ol, and ipsdienol and ipsenol are related to fungal activities in the gallery walls. The amounts of methylbutenol are lower in hindguts from male beetles surrounded by discolored phloem, while ipsdienol and ipsenol are found only in mated males surrounded by unstained phloem. The amounts of ipsdienol and ipsenol in the hindguts could not be correlated with that of any monoterpene hydrocarbon in the phloem wall, not even with myrcene, their suggested precursor. LG EN.

Birgersson, G., Schlyter, F., Bergstrom, G., & Lofqvist, J. 1988. Individual variation in aggregation pheromone content of the bark beetle ips-typographus. J. Chem. Ecol. 14 (9). 1737-1762. ab The total amounts of, and proportions among, components of the aggregation pheromone produced by Ips typographus were found to vary considerably among individuals excised from attacks on standing spruce trees. Chemical analyses of 392 individual male beetles were made by GC-MS. Both unmated and mated males had log=normal frequency distributions in their content of the pheromone components 2-methyl-3-buten-2-ol (MB) and cis-verbenol (cV), since a large fraction of males had a low content. The amount of MB in male hindguts varied independently of cV and the other oxygenated monoterpenes, while the amount of cV covaried with the other pinene alcohols and showed a variation between beetles from different spruce trees. Mated males had, on average, lower amounts of MB than unmated, while the average content of cV in mated males varied with the resin content of their host trees. Ipsdienol and ipsenol were only found in mated males, but in less than 40% and 10%, respectively, of these mated males. Even-aged males exposed to .alpha.-pinene in the laboratory showed slightly less variation in the amounts of verbenols, and the variations in ratio between cV and tV were similar to those among males attacking the same spruce tree. LG EN.

Birgersson, G., Schlyter, F., Lofqvist, J., & Bergstrom, G. 1984. Quantitative variation of pheromone components in the spruce bark beetle ips-typographus from different attack phases. J. Chem. Ecol. 10 (7). 1029-1056. ab I. typographus beetles were collected in the field, separated into 8 attack phases (from beetles walking on the trunk of a tree under attack to those excavating gallery systems with a mother gallery longer than 4 cm), and immediately frozen in liquid nitrogen. 2-Methyl-3-buten-2-ol, cis- and trans-verbenol, verbenone, myrtenol, trans-myrtanol, ipsenol, ipsdienol and 2-phenylethanol were quantified from excised hindguts against an internal standard, heptyl acetate, in the extraction solvent. Methylbutenol, the pinene alcohols, and 2-phenylethanol showed the same pattern of variation between attack phases in males, with the largest amounts present before accepting females and than a fast decline. Ipsenol and ipsdienol were not detected in males before the females were accepted, and the amounts increased when the females start their egg laying. Verbenone occurred only in trace amounts. The beetles were sampled from 5 Norway spruce trees (Picea abies) of differing resin flow. The correlations between the 9 pheromone components and 5 major host monoterpenes in the gut showed that the variation in the amount of methylbutenol, ipsenol and ipsidienol could not be explained by the variation in the amounts of host monoterpenes. In contrast over 80% of the quantitative variation of cis-verbenol, trans-verbenol and myrtenol was explained by the amount of .alpha.-pinene. The 9 pheromone components from 36 individual males were also quantified. Both methylbutenol and cis-verbenol showed a large variation in both amounts and proportions. Females contained trans-verbenol and traces of most other components found in males. When accepted by the male, they also contained a female-specific compound, .beta.-isophorone. Behavioral and biosynthetic implications of the results are discussed. LG EN.

Byers, J.A. 1983. Electronic fraction collector used for insect sampling in the photoperiod induced diel emergence of bark beetles. Physiol. Entomol. 8 (2). 133-138. ab An electron timer and fraction collector consisting of CMOS integrated circuits is described. It converts 50- or 60-Hz AC to real-time pulses in programmable whole-number increments (1, 10 or 60 s) from 3 to 16,659, producing timing periods from 3 s to > 11 days. The fraction collector contains a leaf-switch feedback circuit that automatically adjusts to various gear motor speeds and sample tube spacings so that proper positioning results. Hourly collections by the device of the bark beetles Ips typographus L. and Pityogenes chalcographus L. (Scolytidae) emerging from logs of Norway spruce, Picea abies, indicated that both species emerged with a diel periodicity. A unimodal emergence peak for both sexes of both species occurred at midday in LD (L = light, D = dark) 20:4 at a constant and 80% r.h. (relative humidity). LG EN.

Byers, J.A. 1984. Nearest neighbor analysis and simulation of distribution patterns indicates an attack spacing mechanism in the bark beetle ips-typographus coleoptera scolytidae. Environ. Entomol. 13 (5). 1191-1200. ab The attack sites of the bark beetle, I. typographus, on Norway spruce logs (Picea abies) were observed to be more uniformly spaced than random using nearest neighbor analysis. A computer model which simulated various degrees of uniformity in spatial distribution was compared to the observed attack pattern. The model showed that a mechanism of spacing between attacks, in which beetles need to be greater than a minimum distance of about 2.5 cm away from the nearest neighbor before attacking, can explain the observed distributions in nature. In the model, the distribution of angular directions to the 4 nearest neighbors appeared random, regardless of the degree of uniformity in the spatial distribution. The model for the mechanism of spacing can be applied to other organisms that exhibit uniform distributions. LG EN.

Byers, J.A. 1993. Avoidance of competition by spruce bark beetles ips-typographus and pityogenes-chalcographus. Experientia. Basel. 49 (3). 272-275. ab Bark beetles, Ips typographus and Pityogenes chalcographus, attracted by synthetic or natural pheromone to Norway spruce logs, Picea abies, preferred to colonize uninfested logs rather than logs occupied by these beetles, probably as a means of avoiding intra- and interspecific competition. The aggregation pheromone components of P. chalcographus, chalcogran and methyl (E, Z)-2,4-decadienoate, inhibited the attraction response of I. typographus to its pheromone components (methyl butenol and cis-verbenol), while the converse was not true. However, verbenone released from colonized bark inhibited pheromonal response of P. chalcographus. LG EN.

De Jong, M.C., M., & Sabelis, M.W. 1988. How bark beetles avoid interference with squatters an ess for colonization by ips-typographus. Oikos 51 (1). 88-96. ab Bark beetles aggregate on suitable host trees and their larvae incur severe competition for food from larvae in neighboring galleries. To maximize their fitness parental bark beetles should therefore balance the bark area claimed for their offspring and the probability of being competitively interfered by squatters. It was shown that the unbeatable colonization strategy is to position the gallery relative to a neighbor so as to prevent newcomers from excavating a gallery in between, provided that the probability of interference by squatters exceeds 0.8. A test of the theory was carried out for the case of Ips typographus attacking spruce trees. It was found that the mean (and the modal) gallery distance was close to the critical threshold distance above which a squatter would be able to raise at least one offspring with sufficient energy reserves to find a suitable host. LG EN.

Dickens, J.C. 1981. Behavioral and electro physiological responses of the bark beetle ips-typographus to potential pheromone components. Physiol. Entomol. 6 (3). 251-262. ab Field tests showed (S)-(-)-cis-verbenol and (R)-(+)-trans-verbenol in combination with a 2nd pheromonal component, 2-methyl-3-buten-2-ol, more attractive than the combination with their optical antipodes. Inhibition of response to the attractant component, (S)-(-)-cis-verbenol, by high concentrations of its optical antipode did not occur. No significant differences were noted for response to the attractant, (S)-(-)-cis-verbenol and 2-methyl-3-buten-2-ol, with the addition of either ipsdienol enantiomer or a racemic mixture of ipsdienol enantiometers. Electroantennogram (EAG) studies correlated well with the behavioral studies. EAG recorded from male and female beetles revealed both sexes to have a lower threshold for the pheromone, (S)-(-)-cis-verbenol, than its host terpene precursor, (-)-alpha-pinene. EAG showed a greater number of acceptors for (-)-alpha-pinene in males than in females. EAG at acceptor saturation to the enantiomers of alpha-pinene and the verbenol isomers showed males more responsive to (-)-alpha-pinene, (.+-.)-cis-verbenol and (R)-(+)-trans-verbenol. Significantly greater EAG were elicited in females than in males to (-)-alpha-pinene and (.+-.)- and (S)-(-)-cis-verbenol. No significant differences in EAG of females to the enantiomers of trans-verbenol were noted. EAG showed similar thresholds in males and females to the pheromone component, 2-methyl-3-buten-2-ol; female response at threshold was significantly greater than male response. The results are discussed with regard to olfactory acceptor evolution. LG EN.

Eck, R. 1990. The parasitic hymenoptera associated with ips-typographus in the period of progradation spectrum of species and mortality rates by parasites in some forests of the former gdr east germany insecta hymenoptera braconidae chalcidoidea. Entomol. Abh. (dres) 53 (8-12). 151-178. ab In some forests in the surroundings of Dresden, in the Erzgebirge, the Elbsandsteingebirge and in the Hartz Mountains 13 wasp species were found as parasites or hyperparasites on Ips typographus. Roptrocerus mirus (WALK.) and Metacolus unifasciatus FORSTER are new findings for the G.D.R. Even if altitude and injurious influences correspond, there are differences between the forests regarding spectrum and abundance of the parasite species. The mortality rate in percent of the bark beetles attacked by parasites amounted between 0 and 70%, for the half of all trunks attacked by Ips typographus the mortality was less than 5%. In the months July and August the parasitic wasps can be locally of economical importance for the bark beetles by mortality rates of more than 30%. (Additional species include Roptrocerus xylophagorum, Rhopalophorus clavicornis, Coeloides bostrichorum, Dendrosotor middendorfi, Rhopalicus tutela, R. quadratus, Tomicobia seitneri, Dinotiscus eupterus, Calosota vernalis, Mesopolobus typographi, and Eurytoma arctica.). LG GE.

Furniss, M.M., Solheim, H., & Christiansen, E. 1990. Transmission of blue-stain fungi by ips-typographus coleoptera scolytidae in norway spruce. Ann. Entomol. Soc. Am. 83 (4). 712-716. ab Spores characteristic of tree pathogenic blue-stain fungus, Ophiostoma polonicum Siemasko, and other fungi are visible in scanning electron micrographs of pits on the pronotum and elytra of Ips typographus (L.). Inoculation and reisolation experiments show that O. polonicum was transmitted to (Spruce) logs at generally higher frequencies by live beetles and their excised parts (head, prothorax, or elytra) than by the digestive tract. Other associated fungi isolated at high frequencies from I. typographus were O. bicolor Davidson & Wells, O. penicillatum (Grosmann) Siemasko, Graphium sp., and yeasts. LG EN.

Hallberg, E. 1982. Sensory organs in ips-typographus insecta coleoptera fine structure of the sensilla of the maxillary and labial palps. Acta. Zool. (stockh) 63 (4). 191-198. ab The labial and maxillary palps of the bark beetle, I. typographus, possess a diversified array of sensilla. There are 4 types of sensilla possessing a single tubular body indicating a mechanoreceptive function. The variation of the associated cuticular structures of these sensillar types ranges from long bristles to cavities within the cuticle. Terminal pore sensilla with a supposed mechanosensory/gustatory function and single-walled presumably chemoreceptive sensilla are found on the apical part of the terminal palp segments. A poreless sensillar type is found on the lateral side of the terminal segment of the maxillary palp. The functional capabilities of this sensillar type are presently unknown. LG EN.

Kirkendall, L.R. 1989. Within-harem competition among ips females an overlooked component of density-dependent larval mortality. Holarct. Ecol. 12 (4). 477-487. ab Intraspecific larval competition is commonly believed to be the major component of egg-to-adult mortality in bark beetles. Larval mortality is usually shown to be density dependent. In this study I looked specifically at competition among females in the same gallery system, in a sparse but highly female-biased population of Ips accuminatus breeding in cut pine branches near Kongsberg, southeastern Norway. Supplementary data from a slightly female-biased population in western Norway and a population with intermediate female bias in W. Germany are also provided. Survivorship from egg to adult or pupa was measured in laboratory experiments, for the area in which larvae from different arms potentially competed relative to survivorship in areas away from competition. Survivorship was significantly correlated with both average interarm distance (r2 = 0.76) and food per larva (cm2 per larva: r2 = 0.73). There was no evidence that females could detect the presence of other, nearby egg arms: neither egg spacing (on the arm sides nearest each other) nor interarm distance increased when two arms were near each other. Nor did females distribute themselves optimally within harems, though the distribution of egg arms within harems was significantly different from that expected from random settling, analysis of interarm distances and harem sizes in 1984 branches revealed that a minimum of 34% of arm sides could be expected to suffer considerably reduced larval survivorship due to within-harem competition. Harem size in Ips typographus is reviewed, and data on the distribution of females within harems is presented for Norwegian populations of I. typographus, Orthotomicus erosus and O. laricis. Evidence from the literature is presented to show that uneven distribution of females between harem sides is not uncommon. I suggest that the findings for Ips acuminatus are applicable to a wide range of harem polygynous scolytids, including I. typographus: the factors influencing density cannot be fully understood without taking into account the distribution of females among males and the distribution of females within harems. LG EN.

Klimetzek, D., & Francke, W. 1980. Relationship between the enantiomeric composition of alpha pinene in host trees and the production of verbenols in ips species. Experientia. Basel. 36 (12). 1343-1345. ab Upon exposure to the vapors of oleoresin from 8 conifers, bark beetles, I. typographus and I. amitinus produced verbenol, a terpene alcohol, in a predictable pattern. This pattern changed in relation to the varied enantiomeric composition of the .alpha.-pinene contained in the resin of the various coniferous species. For calibration, defined mixtures of (+)- and (-)-.alpha.-pinene were used to establish the different levels of beetle response in the production of cis- and trans-verbenol. Methodical and ecological implications of the phenomenon are discussed. LG EN.

Krueger, K., & Mills, N.J. 1990. Observations on the biology of three parasitoids of the spruce bark beetle ips-typographus coleoptera scolytidae coeloides-bostrychorum dendrosoter-middendorffi hymenoptera braconidae and rhopalicus-tutela hymenoptera pteromalidae. J. Appl. Entomol. 110 (3). 281-291. ab Spruce bark infested with Ips typographus was collected from Austria and Switzerland in 1987 and 1988 to provide parasitoid material for investigation. Parasitoid emergence in spring indicated that Coeloides bostrychorum was well synchronised in its flight period with susceptible stages of I. typhographus, while Dendrosoter middendorffi emerged earlier than the host beetles. Mating and oviposition are described and an unusual sex ratio for C. bostrychorum is reported. Egg sizes of the three parasitoids are characterised and differences in preferred depth of hosts within the bark are noted. C. bostrychorum with the longest ovipositor can reach all hosts but appears to select only hosts at greater depth than those used by D. middendorffii and Rhopalicus turela. Oviposition occurs almost exclusively on third instar host larvae. Influences of temperature on adult longevity, juvenile development and diapause are presented indicating that R. tutela may be able to continue development through the winter with no true diapause. LG EN.

Lieutier, F. 1978. The acari associated with ips-typographus and ips-sexdentatus coleoptera scolytidae in the district of paris france and the changes of their populations during the annual cycle. Bull. Ecol. 9 (4). 307-322. ab The evolution of mite fauna associated with I. typographus and I. sexdentatus was followed during the annual cycle. The density of acari is higher for I. sexdentatus than for I. typographus. A specificity seems possible for bark beetles or their environment. I. typographus would be accompanied principally by free-living species and I. sexdentatus would be accompanied by phoretic species. The survey of changes of specific composition in the galleries and on insects produced an arrival sequence of various species in the galleries and a sequence of departure to the soil (for the free living ones) or their attachments on insects (for the phorectic ones) . Changes of specific composition induce changes of total density and diversity. The frequency of contamination of Scolytidae by phoretic acari reaches a maximum at swarming. The strength of infection is the same for male or female Ips. LG FR.

Lieutier, F. 1979. Fluctuations of nematode populations associated with bark beetles. Bull. Soc. Zool. Fr. 104 (4). 423-434. ab The qualitative and quantitative specific changes of helminth fauna during the developmental cycle of Ips sexdentatus and I. typographus, both in galleries and in insects are described. The sequences of arrivals of various nematode species in the galleries, as well as the sequences of their attachment on insects are displayed. The development of the frequency of infection in insects, and of nematode density on their host, shows that the contamination of bark beetles is the heaviest at swarming time. LG FR.

Mills, N.J. 1985. Some observations on the role of predation in the neutral regulation of ips-typographus populations. Z. Angew. Entomol. 99 (3). 209-215. ab Sample logs (spruce) were collected from various sites in Bavaria (West Germany) at the end of the each of the first 2 generations of I. typographus L. In 1983. The logs were analyzed by removal of the bark and measurement ofthe densities of scolytids and 2 dominant predators. Scolytid larval mortality averaged 81% in the sample logs and was unrelated to the density of Medetera larvae but increased in relation to clerid (Thanasimus formicarius L.) larval density. Laboratory feeding tests indicated that a single clerid larvae could consume 44 prey during its development and that an estimated 18% scolytid larval mortality was attributable, to clerid predation in the sample logs. LG EN.

Mills, N.J., Krueger, K., & Schlup, J. 1991. Short-range host location mechanisms of bark beetle parasitoids. J. Appl. Entomol. 111 (1). 33-43. ab The host searching behavior and short-range host location by parasitoids of the Eurasian spruce bark beetle, Ips typographus, were examined in order to repeat, using another scolytid-parasitoid system, that observation by RICHERSON and BORDEN (1972b) that host metabolic heat radiation is the principle method of host location by scolytid parasitoids. Differences in searching behaviour of the braconid parasitoids, Coeloides bostrychorum and Dendrosoter middendorffii, and the pteromalid, Rhopalicus tutela, are described. Experiments using both an infra-red scanner and thermistor probes failed to detect "hot spots" associated with susceptible hosts beneath the spruce bark. Deepfreezing and host removal treatments of scolytid infested spruce logs indicated that host vibrational cues were unnecessary for successful host location by parasitoids. The role of volatile chemical cues was investigated using both barriers and implantations on logs. Cellulose barriers did not disrupt host location, while wax barriers disrupted host location for up to 24 h. Similarly, bark from which hosts were removed sustained parasitoid probing for up to 24 h while implantation of hosts into uninfested logs required a considerable lag time before becoming attractive to parasitoids. These results indicate that volatiles are more probably the proximal cues used for host location by the parasitoids of I. typographus and that metabolic heat radiation from hosts was undetectable. LG EN.

Moser, J.C., & Bogenschutz, H. 1984. A key to the mites associated with flying ips-typographus in south germany. Z. Angew. Entomol. 97 (5). 437-450. ab A key identifies 32 spp. of mites associated with flying I. typographus collected from non-destructive pheromone traps in South Germany. Fifteen species were judged phoretic because they were attached to the beetles. The biologies of most of the 32 spp. are unknown, but 3 are potential predators. LG EN.

Mustaparta, H., Tommeras, B.A., Baeckstrom, P., Bakke, J.M., & Ohloff, G. 1984. Ipsdienol specific receptor cells in bark beetles structure activity relationships of various analogs and the deuterium labeled ipsdienol. J. Comp. Physiol. A. Sens. Neural. Behav. Physiol. 154 (4). 591-596. ab The specificity of receptor cells specialized for the bark beetle pheromone component, ipsdienol, was studied electrophysiologically (extracellular recordings) in species of Ips (I. pini and I. typographus). Single cells were tested with both ipsdienol enantiomers, their racemate, and racemates of structurally similar compounds. The 2 cell types, keyed to (+)- and to (-)-ipsdienol, respectively, showed much weaker responses to the analogs, demonstrating the high specialization of the cells. The relationships between the dose-response curves of the 2 types were similar, favoring the concept of particular membrane receptor types (acceptors) in both cell types. The stimulatory efficacy of the various analogs suggested 3 key features of ipsdienol: the free hydroxyl group at C-4, the C-2-C-3 double bond and the diene system attached to C-5 which may be in a cis-conformation. Substituting the C-4 hydrogen by 2H did not affect the stimulatory effect of ipsdienol. LG EN.

Paynter, Q.E., Anderbrant, O., & Schlyter, F. 1990. Behavior of male and female spruce bark beetles ips-typographus on the bark of host trees during mass attack. J. Insect. Behav. 3 (4). 529-544. ab The behavior of 118 spruce bark beetles, Ips typographus, was observed on trees under colonization. Most individuals were followed from when they landed until they entered or left the tree. Both males and females spent most time inspecting crevices and searching for a place to start boring or for a hole to enter. These behaviors accounted for 87 and 70% of all behavioral acts recorded for males and females, respectively. Females entered galleries with males only after a period of pushing at the gallery entrance. Males spent on average 3 min and females 4 min on the bark before entering or leaving the tree. Thirty-three percent of the beetles eventually entered the tree, 31% flew away, 35% dropped from the host, and one beetle was eaten by a predator. The results are discussed in relation to the question of mate choice in bark beetles and to studies on attack dynamics of spruce bark beetle populations. LG EN.

Pettersen, H. 1976. Chalcid-flies hymenoptera chalcidoidea reared from ips-typographus and pityogenes-chalcographus at some norwegian localities. Norw. J. Entomol. 23 (1). 47-50. ab A total of 12 spp. of chalcid-flies were found as parasites or hyperparasites on Ips typographus and Pityogenes chalcographus from Norwegian localities. Of these, 7 are not previously reported from Norway (not indicated). The species Eurytoma blastophagi Hedqv., Roptrocerus xylophagorum Ratz., R. brevicornis Thoms., Dinotiscus eupterus (Walk.) and Tomicobia seitneri (Ruschka) were predominant in the material from the localities examined. The species Eurytoma arctica Thoms. and Heydenia pretiosa Forst. were not frequently found. Eurytoma arctica Thoms. and especially E. morio Boh. and Rhopalicus tutela (Walk.) are species sporadically found on these spruce bark beetles, but known to be more frequent on pine bark beetles. (The remaining species found were Rhopalicus brevicornis Thomson, Karpinskiella pityophtori Boucek and Mesopolobus typographi (Ruschka).

Schlyter, F., & Anderbrant, O. 1993. Competition and niche separation between two bark beetles: Existence and mechanisms. Oikos 68 (3). 437-447. Issn 0030-1299. ab The existence and effects of competition as well as niche separation were investigated in a system of two bark beetle species which aggregate on Norway spruce, Picea abies, to feed on and reproduce in the phloem. In this and other bark beetle systems, there is evidence for competition and intra- and interspecific density effects at normally occurring densities, in contrast to the concept of "density vagueness". Under natural conditions adults of the two species showed a spatial niche separation, where the smaller species, Ips duplicatus, occupied only the top of trees. Regression analysis of adult density patterns of each species showed effects of habitat variables and of density of the opposite species. When breeding at naturally occurring densities (representing both low, endemic, and high, epidemic, population phases), in the same substratum in the laboratory, there was a strong, asymmetric larval competition in favour of Ips typographus. The larger species had a higher reproductive rate in all eight density combinations where the species were reared together. Thus, an adult individual of I. duplicatus would benefit most if it could avoid breeding closely together with L. typographus. Mean offspring body mass decreased for both species as inter- or intraspecific density increased. This resource partitioning between the individuals indicate that the larval competition was of the 'scramble' type. This conclusion is supported by a near complete consumption of the larval food (phloem) and similar egg-laying times (adult re-emergence dates). When the two species were bred separately the two reproductive rates were similar. There were small differences in breeding performance in the laboratory on logs with a diameter between 5 and 15 cm. When given a choice there was a preference by adults of the larger species for larger logs. A clear separation in the aggregation pheromone signal is now known, which allows most colonizing individuals of the smaller species, except the pioneering males, to orient and land on areas outside the range of the larger, supreme competitor. LG EN.

Schlyter, F., & Cederholm, I. 1981. Separation of the sexes of living spruce bark beetles ips-typographus coleoptera scolytidae. Z. Angew. Entomol. 92 (1). 42-47. ab The sexes of Ips typographus were reliably separated by the greater density of bristles on pronotum of the female. This previously undescribed difference was more reliable (4% overlap) for distinguishing between the sexes than the old characteristics of the males larger frontal tubercle (22% overlap) and longer and broader 3rd elytral spine (44 and 84% overlap, respectively). More than 94% of living, handheld beetles were possible to sex, using stereomicroscope, by bristle-density with an accuracy of 98.5%. LG EN.

Schlyter, F., & Zhang, Q.H. 1996. Testing avian polygyny hypotheses in insects: Harem size distribution and female egg gallery spacing in three Ips bark beetles. Oikos 76 (1). 57-69. Issn 0030-1299. ab A majority of females in Ipini bark beetles (Coleoptera: Scolytidae) mate polygynously, although larval competition within harems with gt 2 females is expected to reduce female reproductive success. Models generated for territorial polygyny in birds were examined in order to explain polygyny in bark beetles. At the same time, a test of the general validity of the avian models on an unrelated group of animals is provided. Three levels of models were tested in three Ips spp; 1) male coercion/female choice, 2) cost/no cost of polygyny, and 3) unequal sex-ratio (female biased). A fourth level; compensation/no compensation of female costs could be partly tested. In Ips typographus, I. cembrae, and I. duplicatus mean harem sizes were between 1.9 and 2.8, but between 51 and 79% of females were in galleries with harem size (H) gt 2. The hypothesis of male coercion (1) was not supported due to the non-Poisson distributions of H and the biology of bark living, where females can easily escape male dominance, in favour of female choice. A cost of polygyny (2) was demonstrated: Female egg tunnels were too closely spaced within harems to allow all eggs to develop into adults and the distance between egg tunnels were 50-100% greater between harems than within harems. The unbalanced sex-ratio hypothesis (3) could be rejected because a sizable fraction (3-35%) of males were unpaired or had H lt 2 in the field. At an extreme sex-ratio of 6:1: in the laboratory still as many as 31% of males had only one or two females. On the fourth level (4), compensation of female cost was best supported, but a limitation of compensation by choice due to a 'search-cost' limitation could not be ruled out. 'Deception' hypotheses were ruled out: Female egg tunnels were oriented more evenly than random between the sides of the gallery and eggs were predominantly laid (70%) on sides without within-harem competition. Thus, females acted adaptively based on knowledge of their position relative to other harem females. The compensation for females could be of 'sexy-sons' type in I. typographus, as males with higher H may have higher pheromone content. It is concluded that on the three first levels the 1) coercion, 2) no cost of polygyny, and 3) biased sex-ratio hypotheses could be rejected, while on the fourth level compensation was favoured. LG EN.

Schlyter, F., Birgersson, G., Byers, J.A., Lofqvist, J., & Bergstrom, G. 1987. Field response of spruce bark beetle ips-typographus to aggregation pheromone candidates. J. Chem. Ecol. 13 (4). 701-716. ab Six compounds previously identified from hindguts of unmated male Ips typographus (L.) during host colonization: 2-methyl-3-buten-2-ol (MB) , cis-verbenol (cV), trans-verbenol (tV), myrtenol (Mt), trans-myrtanol (tM), and 2-phenylethanol (PE), were tested for their attractivity in the field with a subtractive method. The amounts of MB and cV released from a pipe trap were similar to those given off from the commercial bait Ipslure as well as that from a Norway spruce tree, Picea abies (L.) Karst., under mass attack. The blend of the compounds became nonattractive when either MB or cV was subtracted, while subtraction of any of the other four compounds had no effect. Addition of ipsdienol (Id) to the blend did not significantly increase the attraction. In a second comparative test, the addition of three compounds as a group (tV + Mt + PE) to MB + cV again had no effect on the attraction, but the addition of Id increased the catch somewhat. Addition of host logs to a bait releasing MB + cV at a rate lower than in previous experiments did not influence the attraction to pipe traps. Sticky traps containing natural pheromone sources (50 males in a log), which released 1-5 mg/day of MB as determined by aerations with deuterated MB as internal standard, were less attractive than a synthetic source releasing similar amounts of MB. LG EN.

Schlyter, F., Byers, J.A., & Lofqvist, J. 1987. Attraction of pheromone sources of different quantity quality and spacing density-regulation mechanisms in bark beetle ips-typographus. J. Chem. Ecol. 13 (6). 1503-1524. ab The density of bark-beetle colonization of a tree could be regulated by a quantitative effect of the pheromone signal from beetles in the tree (cessation of release of attractive pheromone) or by a qualitative effect (production of pheromone components inhibiting attraction). The quantitative hypothesis was tested on Ips typographus by varying the release rate of the two known attractive compounds, 2-methyl-3-buten-2-ol (MB) and (4S)-cis-verbenol (cV). The highest number of beetles were captured at traps with the highest release rates. The catch was nearly proportional to the release of MB and cV at a distance between traps of 12 m or more. At 6-, 3-, and 1.5-m distances between traps deployed in a triangular arrangement there was still a good discrimination between release rates, but relatively more beetles, especially males, were caught on the blank. The lower release rates caught an equal sex ratio while the highest release rate caught only about 30% males. The qualitative hypothesis was tested by releasing the suspected inhibitors ipsdienol (Id) and ipsenol (Ie), from traps in the same amounts as cV. Only small effects were noted for I. typographus. However, the competitor I. duplicatus was attracted to Id and inhibited by Ie, while the predator Thanasimus formicarius was attracted to both compounds. On the other hand, when the ratio of Id or Ie to cV was 10:1 or 0.1:1 rather than 1; 1, they affected the numbers of I. typographus attracted. A small amount of Id combined with the attractants increased trap catch, while large amounts of Id or Ie decreased attraction, especially when combined. Attack density regulation is modeled as an effect of both quantitative and qualitative mechanisms acting in sequence. LG EN.

Schlyter, F., Lofqvist, J., & Byers, J.A. 1987. Behavioral sequence in the attraction of the bark beetle ips-typographus to pheromone sources. Physiol. Entomol. 12 (2). 185-196. ab The functions of the two synergistic pheromone components, (4S)-cis-verbenol (cV) and 2-methyl-3-buten-2-ol (MB), and the role of ipsdienol in the attraction of Ips typographus (L.) (Scolytidae) to pheromone sources were studied in the field. Absolute and relative beetle catches were compared between several traps placed at and nearby a central pheromone source: a pipe trap containing the source, a surrounding sticky trap, a nearby window trap, and four distinct window traps. A higher catch in the outer down-wind distant traps indicated an up-wind anemotaxis to the source. Increased MB release, with cV constant, increased the proportion caught in the central pipe trap, indicating MB as a landing stimulus. Release of MB alone gave a very small catch. Ipsdienol could not substitute for cV in the synergism with MB. An increase of cV, with MB constant, increased the number of beetles caught, but not the proportion caught in the pipe trap. The sex ratio was equal in the window traps, but fell to 30% males in both sticky and pipe traps, showing that a large proportion of the males attracted to the source did not land. The proportion of males in the pipe trap was reduced at the highest cV dose. The results support the idea of each pheromone component having a different relative importance in releasing different steps in the behavioural chain. LG EN.

Solheim, H. 1992. The early stages of fungal invasion in norway spruce infested by the bark beetle ips-typographus. Can. J. Bot. 70 (1). 1-5. ab Healthy Norway spruce trees infested by the bark beetle Ips typographus were investigated weekly for 10 weeks to examine the early stages in fungal invasion. The study was performed in southeastern Noway during an epidemic period. The fungal association consisted of Ophiostoma species and an undescribed Graphium species, which invaded the sapwood in an obvious succession. The pathogenic species Ophiostoma polonicum was the first invader of both phloem and sapwood and was always in the leading edge of fungal penetration into sapwood. Ophiostoma bicolor followed O. polonicum in the sapwood invasion. These species were successively replaced by Graphium sp. 1, Ophiostoma penicillatum and Ophiostoma ainoae. Ophiostoma penicillatum seems to be more adapted to colonizing the phloem than the sapwood. The earliest invaders were the species most frequently carried by the beetles. LG EN.

Tommeras, B.A., Mustaparta, H., & Gregoire, J.C. 1984. Receptor cells in ips-typographus and dendroctonus-micans specific to pheromones of the reciprocal genus. J. Chem. Ecol. 10 (5). 759-770. ab Olfactory receptor cells were studied electrophysiologically in I. typographus and D. micans. The investigation revealed cells which were keyed to (aggregation) pheromone compounds characteristic of the reciprocal genus. Cells keyed to exo-brevicomin were found in I. typographus; cells keyed to (+)-ipsdienol were present in D. micans. Laboratory behavioral tests indicated an attractive effect of the 2 compounds on beetles of the reciprocal genus. In I. typographus the effect of exo-brevicomin predominantly concerned males and enhanced their response to the pheromone Ipslure. It is suggested that exo-brevicomin serves as an interspecific attractant for I. typographus, which may be guided by pheromone compounds of the reciprocal genus in finding suitable breeding material. The function of (+)-ipsdienol in D. micans is more uncertain. It may be either a pheromone or an interspecific messenger. LG EN.

Weslien, J. 1992. The arthropod complex associated with ips-typographus l. coleoptera scolytidae species composition phenology and impact on bark beetle productivity. Entomol. Fenn. 3 (4). 205-213. ab The biology of forest arthropods associated with the bark beetle Ips typographus and the impact of these associates on bark beetle productivity were investigated in the field. Arthropods were allowed access to spruce bolts for different lengths of time, 0, 1, 4, and 8 weeks, following onset of attack by Ips typographus, after which time the bolts were moved to a nonforested area and caged. Arthropods were collected as they emerged from the bolts in autumn and the following spring. At least 32 arthropod species were collected, of which 17 are known to feed on bark beetle brood. The longer the exposure period the more bark beetle enemies and the fewer Ips typographus emerged. Natural enemies were estimated to have reduced bark beetle productivity by 83%. Arrival and emergence patterns and relative impact on bark beetle productivity of different species are discussed. LG EN.

Zumr, V. 1982. Hibernation of spruce bark beetle ips-typographus coleoptera scolytidae in soil litter in natural and cultivated picea stands. Acta. Entomol. Bohemoslov. 79 (3). 161-166. ab Hibernating adults of the spruce bark beetle, I. typographus in soil litter in cultivated and natural stands of Picea were studied in southern Bohemia (Czechoslovakia). Most beetles hibernate directly under felled trees or near the base of standing trees. The total number of hibernating beetles in litter in both types of Picea stand did not exceed 5% of the estimated population of 1 tree. The number of dead beetles found in litter was higher in the natural Picea stands (36%) than in the cultivated ones (16%). Control with insecticides is not considered economic since the number of beetles hibernating in the litter is relatively low. LG EN.

Zumr, V. 1982. Studies on the relation of sexes in beetles of ips-typographus coleoptera scolytidae found in pheromone traps. Anz. Schaedlingskd. Pflanzenschutz. Umweltschutz. 55 (5). 68-71. ab By means of barriere traps baited with 2 types of I. typographus pheromone, Typolur and Pheroprax, nearly 240,000 individuals were trapped between 1979 and 1981 in Bohemian spruce stands. On the whole 64% (Typolur) and 61% (Pheroprax) of the beetles were females. At the beginning of the flying period males predominated, whereas some weeks later the females were prevalent. The latter consisted of individuals founding sisterbroods. Up to 5.2% of females had lost their bristles, showing that they already were through 3 egg-laying periods. LG GE.