THE DANGER OF FLIES 



By ARTHUR E. SHIPLEY, M.A., D.Sc. (Princeton), F.R.S. 

 Fellow and Tutor of Christ's College, Cambridge 



It is one of those facts which not unfrequently occur in science 

 that we know less about the life-history and habits of the 

 commonest insects than we know about scarce and remote 

 species. For instance, the life-history of the common house-fly, 

 one of the most widely distributed insects in the world, is as yet 

 very incompletely known. 



It was Linnaeus who first described this insect and named it 

 Musca domestica, and De Geer who, in the middle of the eigh- 

 teenth centur3 r , first described its transformation. In 1834 

 Bouche described the larva of the insect as living in the dung 

 of horses and fowls. In 1873 the well-known American 

 entomologist A. S. Packard : reinvestigated the question, and 

 L. O. Howard 2 has recently written on the subject. In our own 

 country C. Gordon Hewitt has published a short preliminary 

 account 3 of what will fill a long-felt want when published — his 

 monograph on the House-fly. Packard noted that in the August 

 of 1873 the house-fly was particularly abundant, especially in the 

 neighbourhood of stables. He was able to observe the insects 

 laying their ova in clumps containing some 120 eggs in the crevices 

 of stable manure, " working their way down mostly out of sight." 

 The eggs hatched in about twenty-four hours, but he noticed 

 that those hatched in confinement required from five to ten 

 hours longer, and that these larvae when hatched were smaller 

 than those hatched out in the open. The eggs are oval and 

 cylindrical, one twenty-fifth to one-twentieth of an inch long and 

 about one-hundredth of an inch wide, and of a dull, chalky 

 white colour. 



The little larva has not been seen emerging from the egg- 



1 Proceedings of the Boston Society of Natural History, xvi. 1874. 



2 U.S.A. Department of Agriculture, Division of Entomology, Bulletin 4, 

 New Series. 



3 Manchester Memoirs, li. 1906, p. 1. 



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