EFFECT OF INTERTUNNEL DISTANCE AND NEST-SURFACE ASPECT ON PROGENY PRODUCTION-RATE AND SEX-RATIO IN THE ALFALFA LEAFCUTTING BEE (HYMENOPTERA, MEGACHILIDAE)

Populations of he alfalfa pollinator, Megachile rotundata (F.), nest i n dense aggregations in artificial shelters in alfalfa fields. The clo seness of the nest tunnels in these shelters (5-10 mm apart) fosters w hat appear to be numerous counterproductive interactions among females . By increasing the distance between nest tunnels and patterning the n est-block surface to help orient bees returning from foraging trips, w e sought to reduce interactions and to increase both the number of pro geny produced and the proportion of female progeny. Only the nest-bloc k surface aspect affected progeny production rate; progeny were produc ed at a significantly faster rate in patterned blocks than in plain bl ocks. Intertunnel distance did not affect progeny production rate. Nes t blocks with tunnels 5 mm apart contained a significantly greater pro portion of female progeny than did nest blocks with tunnels spaced far ther apart. Sex ratio of progeny was unaffected by surface patterning of blocks. Females strongly preferred patterned to plain blocks and pr eferred 5-mm and 2-cm intertunnel distances to those of 4 cm. Beekeepe rs and alfalfa growers can increase bee productivity by supplying patt erned nest blocks with intertunnel distances between 5 and 10 mm.