360 STOMOXYS [CH. 



brown. The length varies from 5 to 5-5 mm. The duration 

 of the pupal stage varies from nine to thirteen days under 

 favourable conditions, but may be considerably prolonged by 

 cold. 



A few days before the emergence of the insect the pupal 

 case darkens and splits anteriorly along the lateral and median 

 lines and also across the fourth segment. The front region then 

 falls away and the fly escapes after undergoing a final moult 

 within the puparium. On emergence the fly at first tries to 

 make its way to the surface of any rubbish with which it may 

 be covered. This is chiefly accomplished by means of the 

 frontal sac, which is alternately inflated and deflated, and at 

 the same time the insect pushes itself forward by means of its 

 legs. After it has become free the hairs of the arista are care- 

 fully combed out, and also the .frontal sac and rudimentary 

 wings are cleaned by means of the front pair of legs. Subse- 

 quently the frontal sac contracts and the head assumes a more 

 normal appearance, and then the insect stretches itself to the 

 full extent and pumps air into its body. This air is forced 

 along the nervures of the wings and these finally unfold, being 

 aided by the use of the hind-legs. The fly then remains qui- 

 escent for some time and when the integument and wings 

 are sufficiently hardened it takes flight. 



The duration of the whole life-cycle from egg to imago 

 varies from 25 to 37 days, under favourable conditions of 

 temperature and moisture. 



Methods of destruction. The methods which have been used 

 for the destruction of the common house-fly are also appli- 

 cable to StoniO'ys, with this difference, that whereas in the 

 case of the former, middens and ashpits are notorious breeding 

 places, the stable-fly rarely selects these localities, but chiefly 

 breeds in stable manure and heaps of decomposing vegetation. 

 The numbers of the insect would be considerably reduced in 

 any particular locality, if all stable manure, etc. were care- 

 fully removed at least every seven days, during May to October 

 inclusive. By this means the fly would be prevented from 

 breeding, as the immature stages would be removed together 

 with the manure. In the case of farmyards and country 



