Comparative studies on the developmental rates of the larvae of certain blowflies (diptera: calliphoridae) at constant and alternating temperatures

Abstract

The four blowfly species (named below) were reared as larvae at constant 10º , 15º, 20º and 26º and alternating temperatures (12 hours/day at each) of 10º - 20º and 15º - 26ºC. Larval developmental zero temperatures calculated from the above constant temperatures data were as follows:-Calliphora vicina R-D, 4.8ºC; Calliphora vomitoria L, 5.7ºC; Lucilia sericata Meig. and Phormia terrae-novae R-D. both 10.1ºC. Calculated thermal (day-degree) requirements were also obtained for egg incubation and development of each larval instar for the 4 species. The temperatures or ranges within which each species completed larval development at the lowest day-degree figure, considered to be their most favourable temperatures, for each species were:- C. vicina, constant 10º and 15ºC; C. vomitoria alternating 10º - 20ºC; L. sericata had uniform thermal requirement at 15º , 20º and 26ºC, but at 10ºC failed to develop beyond the lst/2nd instar moult; in P. terrae-novae the most favourable temperature was 26ºC, failing to develop beyond the 2nd/3rd instar moult at 10ºC.Growth rate variation was found to be great within batches of larvae hatched within 30 minutes and reared on excess liver, and weighed at intervals. This variation in C. vicina and C. vomitoria was greater and produced higher S.E.'s at constant than at alternating temperatures, while in L. sericata this effect was not noticeable. In Phormia the S.E. was markedly inversely related to the temperature used. Analysis of growth rate variation in the batches show that there were faster and slower developing individuals with corresponding gradation of final weights achieved, showing that slower developing larvae in the main failed to catch up with the faster larvae. The significance of these variations is discussed.