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Animals use adhesive secretions in a plethora of ways, either for attachment, egg anchorage, mating or as either active or passive defence. The most interesting function, however, is the use of adhesive threads to capture prey, as the bonding must be performed within milliseconds and under unsuitable conditions (movement of prey, variable environmental conditions, unfavourable attack angle, etc.) to be nonetheless successful. In the following study a detailed characterization of the prey capture system of the world-renowned glowworm group Arachnocampa from the macroscopic to the ultrastructural level is performed. The data reveal that the adhesive droplets consist mostly of water and display hygroscopic properties at varying humidity levels. The droplet core of Arachnocampa luminosa includes a certain amount of the elements sodium, sulphur and potassium (beside carbon, oxygen and nitrogen), while a different element composition is found in the two related species A. richardsae and A. tasmaniensis. Evidence for lipids, carbohydrates and proteins was negative on the histochemical level, however X-ray photoelectron spectroscopy confirm the presence of peptides within the droplet content. Different to earlier assumptions, the present study indicates that rather than oxalic acid, urea or uric acid are present in the adhesive droplets, presumably originating from the gut. Comparing the capture system in Arachnocampa with those of orb-spiders, large differences appear not only regarding the silky threads, but also, in the composition, hygroscopic properties and size of the mucous droplets.

An adhesive organ is a prominent characteristic of the genus Idiosepius. Histological, histochemical and ultrastructural methods were applied to elucidate the nature of secretion of the epithelial cells of three Idiosepius species. The adhesive organs of Idiosepius biserialis and Idiosepius pygmaeus consist of five distinct cell types that can be distinguished morphologically and by the composition of their secretions. Histochemical analysis revealed that three cell types contain different sugar units and basic proteins, whereas the interstitial cells lacked secretory material. Acidic and sulfated substances were absent in Idiosepius secretions. The adhesive organ, but not the secretory material of the glandular cells, contained O-linked oligosaccharides. The histochemical analysis of the secretory products suggested that adhesion and release are not effected by a "duo-gland" adhesive system as in Euprymna scolopes. Idiosepius presumably uses a transitory adhesion, perhaps induced by secretion of a highly viscous gel. Release might be caused by contraction of the mantle musculature and/or chemical release mechanisms such as dilutors or enzymes.