First instar nymphs of Monellia caryella (Fitch), Monelliopsis pecanis Bissell, and Melanocallis caryaefoliae (Davis), were exposed to temperatures of 25, 30, 35, and 40° C for up to 9 days. Test aphids were observed for growth, maturity, natality and mortality at each temperature. For three species mortality was low at 25° C but development was slowed; at 30° C mortality increased slightly but development and natality was optimum; at 35° C mortality was greatly increased and maturity was not attained; at 40° C first instar aphids did not survive beyond one day. In further testing with hourly observations at 40° C, M. caryella had 100% mortality after 6 h-exposure, M. pecanis had 100% mortality after 9 h, and M. caryaefoliae survived for 11 h and was the most tolerant of 40° C.

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