Anpassung des Defäkationsverhaltens der Larven von Aleochara curtula Goeze an die raubparasitische Lebensweise im Calliphora-Puparium

Abstract

1. The defecation behavior of the parasitoid larvae of Aleochara curtula in the Calliphora puparium was described. After occupation of the puparium the first-instar larva begins to defecate. With these excrements the larva closes the entry hole. Afterwards the first-instar larva as well as later the second-instar larva defecates liquid excrements only, which gradually ooze into the soil through the closure of the entry hole. At first the third-instar larva defecates liquid excrements in a greater measure. After turning the body this larva gnaws one to four irregular "outlets" within a preference region lateral at the end of the puparium in order to let out these liquids. Later on the larva coats the interior of the puparium wall with the contents of the Malpighian tubules. Some hours later the contents of the gut is voided. Until leaving the puparium no more noticable quantities of excrements are defecated. 2. Experiments to demonstrate the biological importance of the outlets: After covering the preference region for outles with paraffine the third-instar larvae gnaw holes in this region of the puparium wall, which are three or four times as large as normal outlets. Although the activity of gnawing was great 79% or 100% of the larvae died, because they were not able to perforate the paraffin wall or to gnaw outlets in another region of the fly puparium. Experiments with artificial openings indicate that the outlets prevent suffocation of the larvae. 3. A comparative study of the defecation behavior of A. curtula and A. bilineata brought further indications for the hypothesis that the parasitoid life represented by A. curtula larvae is more primitive.