Chemical and Physical Fecal Defense Mechanisms in Insects
Biology 342 Fall 08
Ontogeny
Fecal defense behaviors are most often exhibited in the larvae of insects. As the insects mature, they develop other predator defense mechanisms, such as hard outer shells on beetles, and have no need to retain their frass as a covering or chain.
Frass Chains
Frass chain behavior is observed in larvae in the first to mid-third instar (<5 mm to 20 mm) in Smyrna blomfilida (Machado and Freitas 2001) and from the first to the fourth instar in Eunica bechina (Freitas and Oliveira 1992). This behavior only occurs during a specific period of larval development.
Fecal Shields
Fecal shields are only found in the larvae, and sometimes pupae, of beetles.
Fig. 5. The larva (photo © 2005 Tam Stuart), pupal (photo © 2008 Sharon Perrault), and adult (photo © Bev Wigney) stages of the Plagiometriona clavata. The adult has a brown shell, but there is an absence of any fecal matter.