TOXICITY OF INSECTICIDES TO THE ALFALFA LEAFCUTTER BEE, MEGACHILE ROTUNDATA F. (HYMENOPTERA: MEGACHILIDAE), ESTABLISHED BY THREE EVALUATION METHODS

Abstract

Can. Enr. 120: 29-37 (1988) Oviposition rate (eggs per 9 -degree-day) and fecundity (total number of eggs per 0 )were measured in two populations of Melanoplus sanguinipes (F.) under natural conditions during two seasons (1984, 1985). Differences in fecundity between the two seasons were indirectly associated with differences in time of hatching. In 1985, females hatched earlier and had shorter preoviposition periods, greater longevities, and higher oviposition rates; consequently, fecundity averaged about three-fold greater than in 1984. Longevity appeared to be the most important single determinant of fecundity. Maximum fecundity was 73.2 eggs (equivalent to four pods) and mean fecundity ranged between 10.1 and 28.9 eggs per female.On a estim6 le taux de ponte (oeufs par femelle par degr6-jour) et la f6condit6 (nombre total d'oeufs par femelle) chez deux populations de Melanoplus sanguinipes (E) en conditions naturelles au cours de deux saisons (1984, 1985). Des diffkrences de f6con-dit6 entre les deux saisons ont kt6 indirectement imput6es ? i des diffkrences de temps d'6closion. En 1985, les femelles ont tclos plus t6t et ont montr6 des d6lais de pr6oviposition plus courts, des longtvit6s sup6rieures et des taux de ponte plus 61evBs; par constquent, la f6conditt moyenne a kt6 d'environ trois fois plus 6levCe qu'en 1984. La longCvit6 est apparue cornme le paramktre dkterminant le important de la f6con-dit6. La f6condit6 maximale a kt6 de 73,2 oeufs (Cquivalant h quatre gousses d'oeufs) et la f6condit6 moyenne a vari6 10,l et 28,9 oeufs par femelle.