Regular periods of abdominal contractions recorded from larvae of the bumblebee, Bombus terrestris (Hymenoptera: Apidae)

Abstract

Using an opto-cardiograph combined with an infrared gas analyzer regular bouts of abdominal contractions were recorded from last instar larva of Bombus terrestris. The rate of CO2 release was about 0.7 ml g-1 h-1. The bouts of contractions were of two types: weak extracardiac pulsations and vigorous pumping. The frequencies of pulsations and pumping were 25-35 per min and 8-12 per min, respectively. Bouts of extracardiac pulsations and abdominal pumping were independent of each other and sometimes overlapped. Cardiac contractions (heartbeats) were continuous (57-63 pulses/min). This study suggests that the periodically occurring abdominal contractions play an essential role in respiration and/or in haemolymph circulation in larvae of B. terrestris.