1910 EXTOMOLOGICAL SOCIETY. 33 



be found packed together in one clump. The eggs are pearly white in colour, marked 

 with very fine sculpturing; they are 1 mm. in size, slender and cylindrioally oval, 

 one end being more pointed than the other and along the dorsal side of the egg 

 there are two curved rib-like thickenings of the chorion. The eggs of M. domestica 

 have not the appearance of the grooved wheat grain as stated by several writers. It 

 has been found that horse manure is the special breeding place of flies, but they -wall 

 deposit their eggs and the larvse are able to feed on almost any kind of excremental 

 products and in decaying vegetable substances such as kitchen refuse, especially if 

 such substances are in a fermenting condition. They will also deposit their eggs 

 in decaying fruit and certain food stuffs such as moistened bread, egg, broth, etc. 

 The most important factor which governs the development of the larvse is tempera- 

 ture; a high temperature accelerates the development. It is also affected by moisture, 

 diminution in the amount of moisture retards development and by the character of 

 the larval food and fermentation. The shortest time which I was able to obtain for 

 the development of M. domestica was eight days. This was obtained by keeping 

 the larvae at a constant temperature of 35 degrees C., and the times occupied in 

 the different stages were as follows : — Qgg from deposition to hatching, 8 hours ; 

 whole larval or "maggot" stage 5 days ; the larvae moult twice and the times occupied 

 in the three larval stages were 24 hours, 24 hours and three days respectively; the 

 pupal stage lasted three days. These times are probably as short as will be found 

 \isually under natural conditions. Under unfavourable conditions, with regard 

 to temperature, moisture, etc., the development has been found to extend over 

 several weeks. In no case, however, was it found possible to keep the insects in 

 the pupal stage during the winter nor do I know of any other observer who was 

 able to do so. They invariably pass the winter as adult flies, and under suitable 

 conditions of temperature and the presence of larval food, are able to breed during 

 the winter months. The newly hatched larva measures 2 mm. in length and the 

 average length of the adult larva is 12 mm. It is a typical, conically cylindrrcal, 

 muscid larva, or "maggot," consisting of thirteen segments. It progresses by 

 means of seven pairs of locomotary pads on the ventral side of the body and these 

 are covered with small spines. The intestine of the full-grown larva is very com- 

 plicated as will be seen from the figure thrown on the screen. When the larva is 

 full-grown it retracts the anterior and posterior ends to form a barrel-shaped 

 pupal stage lasted three days. These times are probably as short as will be found 

 from a creamy yellow to a, dark chestnut brown. When the fully develope'd fly 

 emerges from the pupal case it pushes off the front end of the case in two sections 

 by means of an inflated sac in front of the head; this sac is afterwards withdrawn 

 into the head. After emerging from the pupal case the fly crawls about until its 

 wings have attained their permanent form and the body has hardened and dried. 

 In my experiments I found that the flies became sexually mature in ten to fourteen 

 days after their emergence from the pupal state, and four days after coitus with 

 the male they began to lay their eggs which was possible therefore from fourteen 

 days after emergence from the pup*. It will be seen from actual observations and 

 experiments that in hot weather the progeny of a fly may be laying eggs in about 

 3 weeks from the time the eggs from which they were hatched were deposited, 

 and as a fly may deposit about six hatches of eggs in a single season, it 

 is not difficult to realize the millions of flies which a few flies may produce 

 in the hot summer months. These observations indicate two important 

 points : first, the necessity of destroying the first flies that appear in the 

 season, and secondly, the abolition of their breeding places. In our towns and 

 cities owners of stables should be compelled to either remove collections of manure 



