Fungi of the genus Trametes are known as important wood decomposers and are colonized by various species of Coleoptera and other arthropods. The aim of the present study was to investigate the importance of volatile chemical compounds as key attraction factors in recognition and host selection by species of Erotylidae (Dacne bipustulata, Tritoma bipustulata) as well as Cisidae (Sulcacis affinis) and Tenebrionidae (Diaperis boleti). Volatiles from freshly collected Trametes versicolor were collected by headspace sampling technique and identified by combined gas chromatography-mass spectrometry (GC-MS). To evaluate the biological significance of the volatiles we performed behavioural tests and recorded antennal responses of the fungus-inhabiting species by gas chromatography with electroantennographic detection (GC-EAD). The scent of T. versicolor was found to be dominated by sesquiterpenes; in GC-EAD 6 of these compounds elicited reproducible antennal signals in the tested species. Highly significant attraction effects to the fungus, the obtained odour samples and previously described fungal C 8 -compounds were observed in behavioural tests. The possibility to detect these chemical compounds as a key cue for host selection implicate that beetles are able to discriminate between fungi of different age as well as different stages of colonization.

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Members of the cucujiform family Erotylidae possess a whole arsenal of compound integumentary glands. Structural details of the glands of the pronotum of Tritoma bipustulata and Triplax scutellaris are provided for the first time. These glands, which open in the posterior and anterior pronotal corners, bear, upon a long, usually unbranched excretory duct, numerous identical gland units, each comprising a central cuticular canal surrounded by a proximal canal cell and a distal secretory cell. The canal cell forms a lateral appendix filled with a filamentous mass probably consisting of cuticle, and the cuticle inside the secretory cell is strongly spongiose-both structural features previously not known for compound glands of beetles. Additional data are provided for compound glands of the prosternal process and for simple (dermal) glands of the pronotum. A combined defense plus anti-microbial function of the compound glands is tentatively proposed.

The present study provides the first insights into the chemical defensive system of the erotylid beetle, Tritoma bipustulata, and furthermore reports the previously hardly known ability of abdominal reflex bleeding in this coleopteran family. The defensive chemistry of the secretion of pronotal glands, abdominal reflex blood as well as of the haemolymph were analysed by GC-MS. The different secretions were dominated by aromatic compounds; in addition, we detected alkenes, ketones, organic acids as well as a single sesquiterpene. The majority of these detected compounds had strong antimicrobial properties in microbiological assays with entomopathogenic micro-organisms. In feeding bioassays with ants, only benzyl alcohol, benzothiazole, indole and 3-methylindole, detected in the abdominal reflex blood, were significantly deterrent.