HOUSE FLIES, CENTIPEDES, AND OTHER INSECTS, 



45 



Dr. Packard studied the species with some care, and obtained lar^^e 

 numbers of the eggs by exposing horse manure. lie carefully followed 

 the transformations of tlie insect, and gave descriptions of all stages. 

 He found the duration of the e^^^i; state to be twenty-four hours, the 

 duration of the larval state five to seven days, and of the pupal state 

 hve to seven days. The i^eriod from the time of hatching to the exclu- 

 sion of the adult, therefore, occupies, according to Packard, from ten to 

 fourteen days. His observations were made at Salem, Mass. 



As is quite to be expected, as we go further south the house tly 

 becomes more numerous and more troublesome. The number of gen- 

 erations annually increases as the season becomes longer, and with the 

 warm climate the develox^- 

 ment of the larva? becomes ,. /^T 



more rapid. A few rearing 

 experiments were made in 

 this office during the summer 

 of 1895, and it was unexpect- 

 edly found that the house fly 

 is a difficult insect to rear in 

 confinement. Buzzing about 

 everywhere, and apparently 

 living with ease under the 

 most adverse conditions, it Is 

 nevertheless, when confined 

 in the warm season of the 

 year to a small receptacle, 

 not at all tenacious of life. 

 It results from this fact, for 

 example, that it is almost 

 impossible to ascertain the 

 length of the life of the house 

 fly in the adult condition. 

 On June 2G a small quantity 

 of fresh horse manure was 

 exposed in a fly-infested room 

 for a few minutes. The flies 

 deposited their eggs freely and inmiediatel} 



Fig. 14. — iTrfgca domesiica .- a, fiill-fj^rown larva: b, one of 

 its anterior spiracles ; c, siile view of head ; d, hind end 

 of body showing anal spiracles; e, side view of head: 

 /, head from above: fj, head of younof larva from above: 

 /', egjis — all enlarged (original). 



in this substance.' At the 



same time the specimens were confined iii.a glass dish 7.5 inches in diam- 

 eterand 3 inches in height. In this dish was a layer of moist sand, cov- 

 ered with a layer of fresh horse manure, and the vessel was covered with 

 a piece of gauze. On the following morning all the flies, twenty-four in 

 number, were dead, and not a single egg had been laid. A fresh sup- 

 ply of flies was introduced into the same vessel, and the next morning all 

 were dead and no eggs had been laid. The cover was now removed from 

 this vessel and the latter placed in a glass cylinder 14 inches high, the 



' The experiments which follow were conducted by Mr. D. W. C"o(iuilk'tt. 



