192 PHINEAS W. WHITING. 



their white color but have become more contracted. In general 

 the larger species pupate more readily than the Lucilice. 



In no case has there been any correlation of abnormalities of 

 chaetotaxy either with imperfectly formed flies, or with perfectly 

 formed undersized individuals. My counts include several 

 thousand specimens of various sizes and the lack of any correla- 

 tion between number of bristles and size has been so obvious 

 that I have made no measurements to establish this principle. 

 I can, however, furnish numerous specimens of full size with 

 greatly reduced chaetotaxy and numerous minute specimens 

 having the full number of bristles and even additional ones. 

 Walton, 1 however, from a count of ten specimens of Belvosia 

 bifasciata Fabr. concludes that the larger specimens have addi- 

 tional bristles while the smaller individuals are likely to show 

 reduction. As I have not made a study of the parasitic Tachinid 

 flies, with respect to chseiotaxy I am unable to pronounce upon 

 the correctness of this conclusion. Number of bristles appears 

 to be an hereditary matter in the blow-flies, Calliphorinae, 2 and 

 as yet there is no sufficient evidence that environmental factors 

 enter into their determination. 



The normal color changes of the fly after eclosion are of interest 

 and may well be described here for comparison with the abnormal 

 conditions. In all the species bred, the fly emerges from the 

 puparium by pushing off the cap by means of the ptilinum. 

 The insect is at first very small and shrunken, but in a few minutes 

 the ptilinum is withdrawn and the tracheae filled with air. Thus 

 the fly immediately assumes a size much larger than the puparium 

 from which it has just emerged. The color is now white with 

 pinkish and bluish tints, which deepen in a few minutes until at 

 the end of one half hour after eclosion they become deep purple- 

 During the next hour this changes to the normal metallic blue in 

 Calliphorce and Cynomyia, the males of the latter genus gradually 

 taking on more or less of a dark greenish color in the course of a 

 few hours. In Lucilice the condition is very different inasmuch 



'Walton, W. R., '13, "The Variation of Structural Characters Used in the 

 Classification of Some Muscoidean Flies," Proc. Ent. Soc. Wash., XV., I, Apr., 



2 Whiting, P. W., '13, "Observations on the Chsetotaxy of Calliphorinae," Ann. 

 Ent. Soc. of America, VI., 2. 



