Overwinter survival of the boll weevil,Anthonomus grandisBoheman, was compared in the southern and northern Texas Rolling Plains over a 4-yr period. In one test, survival in mesquite (Prosopis glandulosaTorr.) litter was compared to that in broadleaf litter during the winters of 1985–1986, 1986–1987, and 1987–1988. Mesquite litter was a suitable overwintering habitat, and overwinter survival in mesquite litter was comparable to that in broadleaf litter in the southern and northern Rolling Plains. Spring emergence terminated earlier in mesquite litter as compared with that in broadleaf litter in both the southern and northern Rolling Plains. In a second test conducted during the winters of 1986–1989, overwinter survival of four different populations was compared in the southern and northern Rolling Plains. The results of the second test indicated that there are no genetic differences in overwintering ability in Rolling Plains boll weevils. A multiple regression analysis indicated that unique winter weather patterns at each overwintering location were mainly responsible for determining degree of overwintering mortality.