Byers, J.A. 1983a. Influence of sex, maturity and host substances on pheromones in the guts of the bark beetles, Ips paraconfusus and Dendroctonus brevicomis. Journal of Insect Physiology 29:5-13.

mid- and hindgut of male Ips paraconfusus stained violet, Malpighian tubules at left, ventriculus in center, rectum/anus at right. The Malpighian tubules are appressed to the gut at right at the pylorus (the tubules are broken and normally connect from left to right).
Abstract-- Pheromones and metabolites of host (ponderosa pine, Pinus ponderosa) compounds were found in association with the hindgut of both naturally fed and of non-fed, host vapor-exposed bark beetles, Ips paraconfusus and Dendroctonus brevicomis. Much smaller amounts were found in the corresponding heads and midguts. Sex-specific differences in content of pheromones were observed as in earlier studies. Exposure of I. paraconfusus to vapor of a pheromone component, ipsenol and other monoterpene alcohols resulted in their accumulation in the hindgut but relatively very low amounts in the head. The possible sites of pheromone biosynthesis are discussed. Exposure of male I. paraconfusus to vapors of host compounds, myrcene and alpha-pinene, revealed that immature adults do not produce the pheromone components, ipsenol and ipsdienol, as mature adults do while both immature and mature sexes produced another pheromone component, cis-verbenol, as well as trans-verbenol and myrtenol. Immature D. brevicomis adults did not contain pheromones until their exposure to vapors of (-)-alpha-pinene which caused production of trans-verbenol but only about 10% that of mature adults treated similarly. Verbenone, a male-produced inhibitory pheromone of D. brevicomis, apparently was not synthesized from (-)-alpha-pinene in females nor was its synthesis in males enhanced by exposure to this host compound.
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Chemical Ecology