STOMOXYS CALCITRANS: EARLY STAGES 365 



Stable refuse, especially when mixed with horse dung and urine, is a 

 favourite breeding ground for Stomoxys calcitrans, but young larvae are 

 rarely found in the upper layers if they have become dry. It is sometimes 

 only necessary to turn over the superficial layers and expose the damp 

 manure below when a number of females will be attracted to it and will 

 commence to lay their eggs. In Chester Newstead noted that a heap of 

 grass-mowings, the upper layers of which had only recently been deposit- 

 ed, contained a number of nearly mature larvae, whereas a neighbouring 

 heap of horse manure which was dry did not contain any. At the King 

 Institute, Madras, this fly regularly breeds in the sand in a Massachusetts 

 sand-filter bed. The sewage effluent, as it trickles over the sand, forms 

 a green scum, and here the females lay their eggs during December 

 and January. In the Soudan Roubaud notes that the species frequent 

 damp places, some more than others, and that the breeding grounds, as 

 in the case of Glossina, are much more extensive during the rainy season 

 than the dry weather, for they then usually migrate to streams and 

 marshy ground. The females always deposit their eggs in the sand where 

 there is much moisture and organic matter. 



Newstead draws attention to the great difficulty often experienced 

 in finding the natural breeding grounds of this fly ; one of the writers 

 had a similar experience recently at Kodaikanal, South India. The 

 flies were swarming on cattle and horses, yet not a single larva was 

 found in the locality, in spite of the presence of many suitable breeding 

 grounds, such as large collections of horse manure ; in one heap old 

 pupal cases were found, but no larvae. A search was also made in 

 the sand along the banks of streams where there was much organic 

 matter, and where cattle came to drink. Although the flies were 

 seen resting on the leaves of plants no larvae were found. There can be 

 no doubt that calcitrans is somewhat particular as to where it lays its 

 eggs, and that the one essential factor is the presence of an abundance 

 of moisture. 



In the case of the filter bed mentioned above it has been noted that 

 the flies deposited their eggs between 5 p.m. and 7 p.m., rarely during the 



day ; this is, perhaps, explained by the fact that the 



fiu u A A *u Early stages of 



filter bed is exposed to the sun during the greater part stomoxys caicjtrans 



of the day. On alighting on the sand the fly crawls 

 about for a short time, and then, rapidly depressing its abdomen, inserts 

 its ovipositor into the sand and deposits three or four eggs, sometimes a 

 dozen or more ; Newstead notes that the eggs may be laid in a heap. 

 According to Mitzmain oviposition takes place about nine days after the 



