Ecological Studies on the Alkali Bee, Nomia melanderi, and its Bombyliid Parasite, Heterostylum robustum, in Washington1

Publisher Website
Google Scholar
Abstract
Temperature was the most important of the factors affecting time of emergence of the alkali bee and its beefly parasite. Developmental periods became shorter at each higher constant temperature up to 85° F., but development was slowed at temperatures above this point. A wide range of relative humidities did not affect time of development, though saturated and very dry air increased mortality. Depth of the overwintering stages in the soil of a particular site had a slight effect on emergence date, but ecological differences between nesting sites were of more importance. Depth of nesting, vegetation, soil moisture as it affected the condition of the soil surface, and topography all were about equally important in determining the rate of development in the soil. Male bees emerged 3 to 10 days earlier, male beetlies 1 to 5 days earlier than the females, and these differences were borne out in laboratory studies. Both the alkali bee and the beefly react very similarly to the same treatments in breaking the diapause. About 100 days of 50;° F. were required to break the diapause of summer-collected specimens, 60 days for those collected in early October, and no additional cold for those collected in early January. Extending the warm period of those specimens collected in midsummer before the cold treatment stimulated subsequent development. Generally, the beefly has a higher percentage of females than the bee, but beeflies oviposited for a shorter period each day and were quite indiscriminate in their oviposition sites; also, their active season ended 3 to 4 weeks earlier than that of the bees. Percentage of emergence was little affected by vegetation. Beefly larvae, though cannibalistic, preferred to feed upon bee prepupae; opportunities are more numerous for them to feed upon a second bee prepupa than upon each other. Of the natural enemies of both species, mice appeared not to cat beefly larvae, but sought out bee prepupae. Insectivorous birds ate both species, but devoured a larger proportion of beeflies.

This publication has 0 references indexed in Scilit: