POPULATION-GROWTH OF CRYPTOLESTES-FERRUGINEUS AND CRYPTOLESTES-PUSILLUS (COLEOPTERA, CUCUJIDAE) ALONE, OR IN COMPETITION IN STORED WHEAT ORMAIZE AT DIFFERENT TEMPERATURES

Cryptolestes ferrugineus (Stephens) and C. pusillus (Schonherr) were r eared separately at initial densities of 20 or 40 adults each and toge ther at an initial density of 20 adults/100 g cracked wheat or cracked maize at 35, 30, 25, and 20 degrees C and 70% r.h, for developmental periods of 10, 11, 16, or 40 weeks, respectively. Intraspecific compet ition in the 40-adult treatments restricted population growth to level s similar to 20-adult treatments for each species; impact was greatest for C. pusillus on maize at 30 degrees C, where the population of the 40-adult treatment was less than half that of the 20-adult treatment. Both species produced larger populations on wheat than on maize, exce pt for C. pusillus at 35 degrees C; mortality for both species was hig h on wheat at 35 degrees C. Interspecific competition resulted in sign ificantly reduced populations relative to single species populations f or both C. ferrugineus at 30, 25, and 20 degrees C and C. pusillus at 35, 30, and 25 degrees C on wheat and for C. ferrugineus at 25 and 20 degrees C and C. pusillus at 35, 30, and 25 degrees C on maize. During interspecific competition, C. ferrugineus was more successful in mult iplying at 35 and 30 degrees C on wheat and 35 degrees C on maize; bot h species multiplied equally well at 25 degrees C on wheat or 30 and 2 5 degrees C on maize; C. pusillus multiplied best at 20 degrees C on b oth wheat and maize. Cryptolestes pusillus reproduces more effectively alone or in interspecific competition under cool conditions, although C. ferrugineus occurs with much greater frequency in cool Canadian st ored grain, probably because of cold-hardiness and winter survival.