Different developmental strategies in two boreal blow flies (Diptera: Calliphoridae).

The minimum developmental rates of Protophormia terraenovae (Robineau-Desvoidy) and Calliphora vomitoria (L.) were measured at four temperatures: 12.5, 23, 29, and 35 degrees C. Although both species are Holarctic in distribution and hemisynanthropic, there are important differences in the response of their developmental stages to various temperature regimes. The eggs and feeding larvae of P. terraenovae responded linearly to temperatures from 23 to 35 degrees C, but development was retarded at 12.5 degrees C. The feeding larvae took about 11 times longer to develop at 12.5 than at 23 degrees C, indicating poor cold adaptation. The converse is true of C. vomitoria, which took only 2 times as long at 12.5 than at 23 degrees C but failed to complete development at 29 and 35 degrees C. Our laboratory data and field studies of others suggest that, in nature, P. terraenovae and C. vomitoria prefer breeding in larger carcasses as a survival tactic and means of extending their distribution into colder regions.