Female size and fitness in the leaf‐cutter bee <i>Megachile apicalis</i>

Abstract

1. The effects of female size on fitness of the leaf‐cutter bee Megachile apicalis Spinola (Hymenoptera: Megachilidae) were examined using artificial nesting sites in the field. 2. Although female size had no significant effect on female longevity or sex ratio of progeny, it did have a significant effect on fecundity; larger females attained greater realized fecundity than did smaller females. 3. This significant effect of female size on fecundity occurred because larger females produced cells faster than did smaller females. 4. Female size also had a significant effect on egg size; larger females laid larger eggs than did smaller females. 5. Female size had a significant effect on the size of investment in each progeny. The size of investment estimated by brood cell weight was greater for larger females than for smaller females. This pattern was largely absent, however, when the size of investment was estimated by adult progeny weight. 6. Female size had a significant effect on nest usurpation behaviour; larger females had a higher capacity to usurp nests than did smaller females.