152 Psyche [October 



The female will readily oviposit in many species of dipterous 

 pupa?. Evidently it has no preference. In addition to Stomoxys 

 calcitrans the following species have been parasitized experimen- 

 tally: Musca domestica Linn., Hcematobia serrata Desv., Helicobia 

 quadrisetosa Coq. and Pseudopyrellia cornicina Fabr. In one test 

 a number of puparia of different species of flies were mixed with 

 those of Stomoxys calcitrans and all were put under a glass bell 

 jar in the laboratory. A number of parasites were introduced and 

 observations made in order to ascertain if any preference was 

 shown. In this case, as well as when different pupse were placed 

 in small tubes with parasites, no discrimination between the dif- 

 ferent species was apparent. 



In nature the stable fly is undoubtedly the principal host of 

 the parasite. This is evidently due to the breeding habits of this 

 fly. As has been stated, the stable fly breeds largely in rotting 

 straw or manure which contains much straw. The loose texture 

 of this material allows the parasites to gain access to the puparia 

 with ease. On the other hand, the breeding habits of the species 

 which have been found experimentally to act as hosts of this par- 

 asite, are quite different. For example, Musca domestica, Hcema- 

 tobia serrata and Helicobia quadrisetosa breed mainly in dung or 

 other matter which is of compact texture. By the time the 

 larvse are ready to pupate the material in which they are breeding 

 becomes quite compact. This prevents, to a great extent, the adult 

 parasites from entering the substance in order to reach the host, 

 except when the mass of breeding material is accidentally scat- 

 tered or if some straggling specimens happen to pupate so as to be 

 partially exposed. In nature this condition is not the rule, hence 

 we find the parasite attacking most commonly those species which 

 are readily reached. 



Development. 



The length of the developmental period of the parasite varies 

 greatly, according to the temperature experienced. An egg (see 

 Plate I fig. 2) which was probably of this species has been re- 

 moved from the body of a fly pupa. A number of observations 

 have been made to determine various points in the developmental 

 period of the parasite. 



