Chemical ecology
In the field of chemical ecology we investigate defensive substances and strategies of thrips (Thysanoptera) and other plant sap-sucking micro insects. The main focus lies on the thrips suborder Tubulifera. Larvae and adults secrete anal droplets that are retained between specialized setae at the tip of the abdomen and then dabbed on predators as a defense. The thrips can place the droplet on a predator in front of it by curling its abdomen over its head. Thrips of the suborder Tubulifera have a special long tube-shaped apical abdominal segment which they use in this context. Secretions of various species of the family Phlaeothripidae (Tubulifera) contain long-chain, solid acetates, which are dissolved in liquid long-chain alkanes, e.g. hexadecyl acetate with pentadecane (1:2) in Gynaikothrips ficorum.
In the Phlaeothripid species Suocerathrips linguis (Fig. 1) we found several other acetates, e.g. (11Z)-icosa-11,19-dienyl acetate as main component. This acetate was never found in nature before. It does not need any solvent because it remains liqud until -15 °C because of the Z double bond at the middle of the molecule. The function of the terminal double bond is still unknown.
Further reading:
DOI 10.1007/s00049-009-0014-x
The phlaeothripine Callococcithrips fuscipennis (Fig. 2) has a special lifestyle. The thrips lives in the sticky wax masses of females of the felt scale insect Callococcus acaciae. Thus, we estimated no defensive secretion. But we found, besides alkanes and esters of long-
chain unbranched alcohols, diastereomers of the iridoid dolichodial in the anal droplets. Iridoids have not been previously identified in Thysanoptera. They are known as strong insect repellents.
Further reading:
DOI 10.1007/s10886-008-9494-3