OBSERVATIONS ON BLOW FLIES. 185 



The second main line of investigation was concerned with 

 coloration in the adult flies and showed results as follows: 



The first color assumed by the adults after their integument 

 has hardened is a deep purple which rapidly changes to dark 

 metallic blue in the larger forms experimented upon, Cynomyia 

 and Calliphora, becoming greenish after a short time in the males 

 of Cynomyia. In Lucllia the purple passes rapidly into a bright 

 green, which is later replaced by more or less bronze. The 

 degree of this bronzing tendency is evidently of an hereditary 

 nature as different strains vary in this respect and selection is 

 here effective. The environmental factors, light and tempera- 

 ture, seem to have no effect upon the degree or rapidity of this 

 process. 



The experiments recorded in this paper were performed upon 

 the various species of blow-flies common in New England, especial 

 attention being given to the common green-bottle fly, Lucilia 

 sericata. 1 



larvae of Lucilia sericata and Cynomyia cadaverina, which have been allowed to feed 

 on all the fish that they would eat, on attaining the migration stage, have pupated 

 within two or three days and have emerged from the pupae in due course despite 

 the fact that they have had plenty of opportunity to overeat. 



In Table IV., Series I, Herms records the mean weight of larvae of Lucilia at 

 the end of a feeding period of 60-72 hours as 38.183 milligrams, from 256 counts. 

 This weight is regarded as the optimum for development. Among this series were 

 a number that delayed pupation. These comprise Series 7. When weighed (there 

 were 64 individuals) the mean weight was 33.59 milligrams. Although this weight 

 is lower than the mean of Series i, it is considered, that at the time of migration it 

 must have been higher and that the difference is due to loss of moisture during the 

 extended migration period, which had up to the time of weighing been twelve days. 

 At the end of twenty days in the larval period as against a normal of about six 

 days, 39 of these larvae pupated, the rest being dead. // is assumed "that these 

 larvae were beyond the optimum weight, and for this reason pupation was deferred." 



1 Experiments were performed upon Lucilia sericata Meig., L. sylvarum Meig., 

 L. ccesar L., Calliphora erythrocephala Meig., C. viridescens Desv., C. vomitoria L., 

 and Cynomyia cadaverina Desv. Nothing has been done with the Sarcophagidae, 

 L. str., the flies named being included in the Calliphorinee of the Muscidee. Herms 

 groups them all under the Sarcophagidae, stating that he follows Girschner in this 

 matter; but Girschner includes Calliphorinae as his second group and Sarcophaga, 

 Dexia, etc., as his fourth group under the family Tachinidae, dropping the name 

 Sarcophagidae. (Girschner, E., '93, "Beitrag zur Systematik der Musciden," 

 Berl. Ent. Zeits., XXXVIII. , 3). 



While the work of Herms is said to have been done on L. ccesar, this is probably 

 not correct as this species is relatively infrequent as compared with L. sericata, 

 and Herms's material was collected from fish put out where all flies had ready 



