Attraction and repulsion: preliminary observations on semiochemicals and lacewing evolution (Neuroptera: Chrysopidae)

Chrysopidae (green lacewings) are a widespread and diverse family of Neuroptera. The holometabolous insects have a distinctively different life style in their larval and adult phase. Whereas adults are mostly nectar and pollen feeders the larvae are predacious, feeding on aphids and other small, soft-bodied insects, which enables a commercial use in pest control. Because of the adults repelling odor when caught, some green lacewings are also called stinkflies. The substance behind this smell is a combination of semiochemicals (allomones) which both sexes can secret from specialized glands. Besides the use as a defense mechanism semiochemicals (pheromones) are speculated to play a role in the sexual behavior of Chrysopidae. Several types of chemicals have been found to attract chrysopids and as a result mostly males often end up in traps originally intended for fruit flies. The semiochemicals secreted for attraction and repulsion are probably the result of biosynthesis of these substances. One example is methyl eugenol (a phenylpropanoid common in many plants), which is currently known to attract males of Sencera Navas, 1925, Parankylopteryx  Tjeder, 1966, Mallada Navas, 1925 and Cunctochrysa Hölzel, 1970. Though the exact effect is not yet discovered, it is speculated to play a substantial role in sexual attraction. The ability of synthesizing semiochemicals as well as their composition varies between chrysopid taxa, but the specific pathways and to which extent it occurs in the family are not well known. Here we review semiochemicals in Chrysopidae and speculate on the possible phylogenetic information associated with this trait.