Vol. xxi] ENTOMOLOGICAL NEWS 411 



The Development of a Green-Bottle Fly. 

 By MARY O. ALLEN. Milwaukee, Wisconsin. 



The following life history is the result of investigation 

 extending over a period of four summers under quite vary- 

 ing conditions. Knowing that several species of Diptera live 

 on decaying matter, meat, both raw and cooked, was left ex- 

 posed in several different places and at different times in 

 order to obtain eggs, and these were usually forthcoming after 

 a night's exposure if the conditions were right. Pieces left 

 on the ground were often eaten by cats or dogs, and one 

 small piece was drawn into the earth by a very large earth 

 worm as was known by the fact that it had been put on a 

 small piece of cloth, and the corner of this cloth was drawn 

 into his hole and the worm was in this hole. Those portions 

 of meat placed three or four feet above the ground were not 

 touched, probably because the pupal state is passed under the 

 surface of the earth if possible, and the larvae could not drop 

 down safely as can many caterpillars ; also meat left in very 

 sunny places was not visited, so it would seem as if the fly 

 must know that sun and drought are fatal to her offspring. 

 She herself disports in the sun most of the day. Whether 

 the meat is raw or cooked seems to make no difference, but 

 the green-bottle will not lay its eggs upon vegetable matter, 

 although they may be seen extracting food from vegetable 

 refuse. They must determine where the host is by the sense 

 of smell. 



The earliest that eggs have been obtained is June I3th. 

 and it seems probable that they are usually laid in the early 

 morning, as only once has a fly been seen depositing eggs. 

 In this case she began by walking over and over the meat, 

 fully forty or fifty times, feeling all the time with her ovi- 

 positor until she found just such a crevice as she wished. 

 Into this she deposited about thirty eggs in irregular rows, 

 then walked on continually feeling her way. She kept this 

 up for two hours, depositing all the way from four to fifty 

 or more eggs in each place. She probably laid no less than 

 four hundred eggs, but they were not actually counted. 



