220 



MR. A. M. ALTSON ON THE LIFE-HISTORY AND 



The Adult. — Ernergence of the Adult. — "In geiiei-al, it may be 

 stated that the adult parasites emerge from the host puparium 

 through from 1 to 3 circular holes, situated variously, usually in 

 the dorsal or dorso-lateral aspect ; and when more than one exit- 

 hole, the two or three are usually scattered or widely separated. 

 The manner of emergence does not differ for sex. The exit-hole 

 varies in diameter from 0*75 to 1'50 mm. ; it is usually larger and 

 single when the host is Musca or Chrysoinyia and smaller when 

 Phormia, though this difference may be more apparent than real. 

 Individual exit-holes may of coui se vary considerably in shape ; 

 for rarely it may involve the whole of one end of the host 

 puparium, and is then relatively very large and iriegular. The 

 margins of the exit-holes are always jagged or serrate, showing 



that the adults gnaw their way out In regard to the time 



of emergence, the males usually emerge from 2 to 20 hours 

 earlier than the females, a few emergirig some hours previous to 

 the simultaneous emergence of the majority, but there is con- 

 siderable variation in individual cases. Thus some males may be 

 the last to emerge, but the tendency is for them to emerge earlier 

 than females." (6.) 



In the laboratory the number of exit-holes was not limited 

 to three, four and five have been seen, and the exit-holes, con- 

 sequently, dorsal, ventral, or lateral (text-fig. 16). 



Text-£gure 16. 



Puparium witli two exit-lioles latero-ventrally. N. hrevicornis. 

 Greatly magnified. Original. 



Both sexes emerge with the wings fully expanded. 



Larvae have been found in pnparia from which — several weeks 

 or months previously — adults had emerged. If this takes place 

 under natural conditions, it would appear that these have very 



