COMPARATIVE MORTALITY RESPONSES OF 2 COOK ISLAND FRUIT-FLY (DIPTERA, TEPHRITIDAE) SPECIES TO HOT-WATER IMMERSION

Mortality responses of 2 species of fruit fly, Bactrocera melanotus (C oquillett) and B. xanthodes (Broun), to heat treatments were investiga ted using hot water immersion. The eggs (young or mature), 1st, 2nd, a nd 3 ages (early-, mid-, and late-aged) of 3rd instars were immersed i n hot water at selected temperatures in the range 43-48 degrees C. B. melanotus mature eggs were more heat-tolerant than all other life stag es of either fruit fly species except B. xanthodes early-aged 3rd inst ars at 48 degrees C, where the difference was not significant. At temp eratures less than or equal to 45 degrees C, 1st instars of both fruit fly species were more heat tolerant than 3rd instars (all ages), wher eas at 48 degrees C the estimated times for 99% mortality for 1st and 3rd instars were similar. B. xanthodes young eggs were significantly l ess tolerant to heat than all other life stages of the same species, w hereas for B. melanotus young eggs were less tolerant to heat than lat e-aged 3rd instars, 1st instars, or mature eggs. B. melanotus eggs wer e more heat tolerant than B. xanthodes eggs, whereas the reverse was t rue for larval stages.