SURVIVAL OF DIAPAUSING AND NONDIAPAUSING BOLL-WEEVILS (COLEOPTERA, CURCULIONIDAE) SUBJECTED TO FREEZING TEMPERATURES

Boil weevils, Anthonomus grandis grandis Boheman, were subjected to fr eezing temperatures of 0.0, -2.5, -5.0, -7.5, and -10.0 degrees C in a cold bath. Survival of diapausing and nondiapausing adults was compar ed after exposures of 2-, 4-, 6-, and 8-h duration. Diapausing and non diapausing individuals could be separated by exposure to -7.5 degrees C for 6 h; diapausing adults were alive and able to walk after this tr eatment, whereas nondiapausing adults were dead or unable to stand. In the diapausing group, young boil weevils (36 d old) were more toleran t of freezing conditions than were older (110 d old) boil weevils. In a 2nd test, diapausing adults were exposed to these 5 temperatures for 8-72 h. Roll weevils did not survive exposures greater than or equal to 40 h duration at -10.0 degrees C. In a 3rd test, diapausing boil we evils were subjected to temperatures of 0.0, -2.5, -5.0, and -7.5 degr ees C for 4, 8, 16, and 24 h/d for 2, 6, 10, 14, and 18 consecutive da ys. At the end of the daily freezing exposure, adults were removed fro m the cold bath and held at 4.4 degrees C. No boll weevils survived th e treatment combinations of -5.0 degrees C for 24 h/d for 14 d and of -7.5 degrees C for 16 and 24 h/d for 10, 14, or 18 d. However, tempera tures this low for this length of time are not common in the Texas Rol ling Plains. In the regression equation relating survival with the var ious exposure conditions, the linear and quadratic components for temp erature were primary variables affecting survival in each of the 3 tes ts.