PSYCHE 



VOL. XXIX. AUGUST 1922 No. 4 



POSSIBLE PEDOGENESIS IN THE BLOW-FLY, Calliphora 

 enjthrocephala MEIGEN. 



By G. H. Parker. 



Zoological Laboratory, Harvard Universit3\ 



In the early autumn of 1918 I prepared a number of cultures 

 of larvae of the common blow-fly, Calliphora erythrocephala, and 

 in several of these cultures the numbers of maggots seemed to 

 exceed considerably the numbers of eggs that had been intro- 

 duced. This aroused the suspicion that some unusual form of 

 multiplication such as polyembryon}^ or pedogenesis was oc- 

 curing and to test this definite experiments were attempted. 



On November 25, 1918, thirty bottles closed with aluminum 

 caps through each of which a minute hole had been punched, 

 were supplied with small pieces of fish-meat carefully inspected 

 to see that they carried no fly eggs. In each of twenty of these 

 bottles a single blow-fly egg was placed, ten bottles having been 

 retained as checks. On December 9, 1918, all these bottles were 

 carefully examined. Seven of the infected bottles contained no 

 maggots, ten contained each one maggot, one contained two 

 maggots, another three, and a third four. One of the check 

 bottles, however, contained nine small maggots showing that 

 the procedure that had been followed was defective. Either un- 

 seen eggs had been accidentally introduced with the meat, or 

 flies had slipped eggs into the bottle through the small hole in 

 the cap. Hence the increased numbers in several of the infected 

 bottles could not be said to be due to multiplication within the 

 bottle itself and this type of test was, therefore, abandoned. 



In the spring of 1919, with the return of the flies, a new 

 procedure was employed. Fifty clean quart jars were prepared 

 by pouring into them enough coarse sand to cover their bottoms. 

 This sand had previously been sterilized by baking. Into each 



