THERMAL TOLERANCE IN MACROCENTRUS ANCYLIVORUS ROH. (HYMENOPTERA: BRACONIDAE)
The lethal effects of high temperatures were investigated on Macrocentrus ancy-livorus Roh., a parasite of the oriental fruit moth. Day-old adults were exposed to uniform high temperatures for fixed periods ranging from 15 min. to 8 hr. in different tests. Temperatures investigated ranged from 30° to 45 °C. The insects had been reared under uniform and rigidly specified conditions at constant temperatures. After exposure all the test insects were removed, put in bottles, and provided with 10% sucrose solutions as food. Mortality was recorded 24 hr. later. Sexes were kept separate. Tests at all temperatures and exposure times were carried out both in dry and in moist air. At temperatures up to 34 °C. mortality was light even at the 8-hr. exposure. At 44 °C. almost 100% mortality was recorded at the 1/2-hr. exposure. Between these limits mortality increased with higher temperature or lengthened exposure time; it was generally greater in dry air than in moist. Females were more resistant than males. Thermograph records from the peach growing areas of the Niagara peninsula showed that only in exceptionally hot summers could conditions cause appreciable death from the direct action of temperature alone.