Easily damaged integument of some sawflies (Hymenoptera) is part of a defence strategy against predators

Abstract

During evolution insects have developed an impressive set of mechanisms to defend themselves against natural enemies. This includes adaptations in their phenology, behaviour, morphology, physiology, and chemistry (Evans and Schmidt 1990). Typically, at least two such traits occur jointly, so that one can speak about a real defence strategy. Yet, defensive traits per definition increase an insect's fitness, but taken alone one trait may be disadvantageous. A new kind of defence strategy was discovered recently in larvae of some sawflies (which are herbivorous Hymenoptera) of the family Tenthredinidae. So far unknown in other insects, it was called easy bleeding and defined as a low mechanical resistance of the whole body integument, by which slight mechanical damage of the integument is enough to provoke the release of hemolymph at this given spot (Boevé and Schaffner 2003; Fig. 2.1). © 2009 Springer Science+Business Media B.V.