39 



Packard, writing in 1873, stated that there were only three works in which its 

 life-history was given. The first was published by DeGeer, in 1776, and satisfactorily 

 described the various stages, but did not give the time occupied by each. The following 

 is his description of the manner in which he discovered the habitat of the larvae : — 



"In considering the enormous abundance of these domestic flies, which especially 

 appear in the months of July and August, it is astonishing that no person ha3 hitherto 

 discovered their larvae. I searched uselessly for them myself everywhere during several 

 years, and then it was only chance that caused me to discover them in the same months 

 of July and August of the year 1750, when having, according to the instructions M. de 

 Eeamur in the 'Art of Hatching Domestic Birds,' made one day a heap of horse manure 

 to hatch some chickens, I saw flying upon and all around it a great number of these 

 flies, which having aroused in me the curiosity to stir up the heap, I found in it abun- 

 dance of larvae with the head of a variable form ; and having enclosed several of them 

 in a sand-box half filled from this same dung-heap, I observed that some days after they 

 had made cocoons of their own skin, from which came out afterwards true domestic 

 flies, such as those which I have just described. The larvae of this species live then in 

 manure, but only in that which is very warm and moist, or to say it better, that which 

 is in a complete fermentation, as was that which immediately surrounded the cask in 

 which I hatched successfully some hen's eggs j at least I have never met with them in 

 dry manure nor in- the earth." 



The second work was published several years later by a German named Keller, and 

 contained excellent figures of the larvae and pupae. The third, also by a German named 

 Bonche, appeared in 1834, but the figures in it (copied in the " Guide to the Study of 

 Insects ") were drawn so poorly as to be unrecognizable. Packard, not having seen 

 Keller's work, was of impression that the poor figures of Bonche were the only ones 

 published, but I have before me a little book, entitled the " Earthworm and House-fly" 

 (published in 1858 by James Samuelson, assisted by J. Braxton Hicks, M.D., F.L.S., etc.), 

 which reproduces Keller's figures from a copy of his work in the British Museum, and 

 shows us that they were excellent ones. There are also some very fine microscopic 

 illustrations of various parts and organs of the house-fly in the little treatise just men- 

 tioned drawn by the author. 



As recently as 1873 the transformations of the house-fly had not been given by any 

 American naturalist ; but in the autumn of that year Packard worked out its life-history, 

 and described its different stages in a paper published in the Proceediugs of the Boston 

 Society of Natural History. This paper was accompanied by a large plate of excellent 

 figures, and to it I am indebted for many of my facts. 



Every one has noticed that flies are particularly numerous in the vicinity of stables, 

 and investigations have proved that it is in the decomposing vegetable matters which 

 there accumulate that the eggs of the fly are deposited and that the larvae live. Keller 

 reared them successfully in a jar of moist decomposing wheat, but the material used by 

 Packard was that which furnishes the majority of flies with a breeding place, viz., 

 fresh horse manure. In the crevices of thi3 substance the fly deposits her eggs to the 

 number of about 120. These eggs are elongate, oval cylindrical: a little smaller and 

 more pointed at the anterior than at the posterior end. Each is from to of an 

 inch long and of an inch in diameter, being slightly smaller than the egg of the 

 meat-fly which we see attached to meat. In colour it is a chalky white, and opaque, so 

 that the earlier embryonic changes cannot be observed, as in the case of many insects 

 having transparent eggs. With suitable conditions of heat and moisture the egg hatches 

 in 24 hours, and there slips out an active, semi-transparent little maggot (as the larvae 

 of all flies are called) of an inch in length. About 24 hours later the larva, grown 

 too big for his jacket, casts it aside, and now measures from to of an inch, and 

 is slenderer than during the preceding stage. This second stage lasts from 24 to 36 

 hours, when another moult takes place, after which the larva lives three or four days 

 and attains a length of from £ to T 4 ff of an inch. The larva has a small conical head, 

 bearing minute, two-jointed antennae, and below them three small fleshy tubercles — 

 probably representing or foreshadowing some of the future mouth-parts, of which there 



