Cuckoo wasps (Chrysididae, Hymenoptera) are known for their parasitoid or cleptoparasitic life histories. Indeed, the biology of only a few species has been studied in detail and often only little more is known than the host species. By mimicking their hosts’ cuticular hydrocarbon (CHC) profiles, species that parasitize single (or a few closely related) host species manage to deceive their hosts. However, the variability of the CHC profile in generalist cuckoo-wasp species is still unknown. Here, we used gas chromatography—mass spectrometry (GC-MS) and DNA barcoding to study intraspecific variation in cuticular hydrocarbons of one less host-specific species of cuckoo wasps, Trichrysis cyanea. Cuticular hydrocarbon (CHC) patterns were found to differ between males and females. Additionally, we found chemical polymorphism among females, which formed three distinct chemical subgroups characterized by different alkene patterns. A lack of divergence in the DNA barcoding region suggests that these different chemotypes do not represent cryptic species. Whether this intrasexual CHC-profile variation is an adaptation (mimicry) to different host species, or simply signaling the reproductive status, remains unclear.

The oil gland secretion of the oribatid mite Nothrus palustris is known to show the phenomenon of juvenile–adult polymorphism, i.e., juvenile instars produce secretions predominated by geranial, whereas adults secrete dehydrocineole along with a number of chemically unidentified compounds. We here re-analyzed the secretions of adult N. palustris by GC–MS and NMR spectroscopy, eventually identifying the unknown compounds as p-menthane monoterpenoids. The major components were two isomeric 6-isopropenyl-3-methyl-cyclohex-3-en-1-yl formates (= p-1,8-menthadien-5-yl formates), which accounted for about 75% of the secretion. These were accompanied by five additional, only partly identified p-menthanes (or p-methane-derivatives), all of which represented minor or trace components. In addition, adult secretions contained two C21-hydrocarbons, 1,12-heneicosadiene (major) and a heneicosatriene (minor). Menthane monoterpenoids represent a novel sub-class of terpene compounds in the oil gland secretions of Oribatida. In case of N. palustris, we assume that both geranial and p-menthane monoterpenoids arise via the mevalonate pathway which obviously shows a split at the level of geranyl pyrophosphate, leading to geranial in juveniles and to p-menthanes in adults. The significance of methane occurrence in oil glands as well as the taxonomic distribution of juvenile–adult polymorphism in oribatid oil gland secretions is discussed. The latter phenomenon—i.e., “chemo-metamorphosis” of secretions—is not known from early- and middle-derivative Oribatida nor from Astigmata, but appears to be more common in some derivative desmonomatan and brachypyline oribatid groups.

http://www.eje.cz around 3000 described species. They parasitize sawfl ies, aculeate wasps and bees and in some cases also silk moths and stick insects (Kimsey & Bohart, 1990). So far, there are no reports of sexual dimorphism and/or intra-sexual variation in wing size and morphology of any chrysidid wasp. In the present study, we focus on one species of Chrysididae, Trichrysis cyanea (Linnaeus, 1758). This is a palearctic species and unlike many other cuckoo wasps, has a broad range of hymenopteran hosts, belonging mainly to Pompilidae (Trypoxylon) and Crabronidae (Auplopus and Deuteragenia) (Pauli et al., 2019; Wiesbauer et al., 2020). A recent study (Fröhlich et al., 2022) reports sexual dimorphism in cuticular hydrocarbons in T. cyanea. Furthermore, female T. cyanea express several markedly different profi les of cuticular hydrocarbons, the reason of which is still unclear, although adaptations (mimicry) to different host species or signalling of the females' reproductive status have been hypothesized.Here, using geometric morphometrics on photographs of forewings taken with the aid of a newly developed tool that can be used on type-material as it does not require the removal of wings from specimens, we studied intraspecifi c variation in wing morphology and size in T. cyanea from eastern Austria. These fi ndings are discussed in the context of the current state of knowledge of this species' biology.