Calorimetric investigations of insect metabolism and development under theinfluence of a toxic plant extract

The cyclic gas exchange in the diapausing pupae (DP) of the cabbage butterf ly Pieris brassicae was monitored by use of simple and sensitive twin diffe rential calorimeter combined with automatic respirometer. Usually, the peri odic CO2 releases in DP occurred as large, intermittent and micro bursts (i .e. in the form of respiratory cycles). By treating the DP with low doses of the extracts of the marguerite Tanacet um roseum the large cycles of gas exchange were abolished, but the intermit tent and micro bursts were preserved. These treatments did not result in an y neuromuscular hyperactivity. After the treatment the body mass loss of DP increased from 1.72+/-0.16 (females (2x) and 2.23+/-0.31 (males 2x)) mg g( -1) day(-1) for the untreated pupae to 2.25+/-0.38 (females (2x) and 3.05+/ -0.76 (males 2x)) mg g(-1) day(-1) for the treated ones. All the DP who survived the treatment developed into pharate stages, but ad ult emergence failed. The untreated and control DP kept at room temperature s (20-25 degrees C) did not initiate adult development and died after havin g lost more than 25% of initial body mass. It is assumed that pyrethrum, a nonhormonal agent, acts directly on the bra in, stimulating the release of the prothoracicotropic hormone (PTTH). (C) 1 999 Elsevier Science B.V. All rights reserved.