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 25.degree. 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.