OBSERVATIONS ON BLOW FLIES. 187 



for the fact that in many cases the full-sized imperfectly formed 

 specimens have come from pupae kept damp. Nor can this be 

 due in all cases to drying of the larvae in the prepupal stage as 

 will appear from experiment 1 91 2-f recorded below. 



Rarely has there been any considerable prolongation of the 

 pupal stage in my experiments. Eclosion has taken place in 

 approximately the time expected varying slightly with the species 

 and the temperature. In one case, however, a few pupae of L. 

 sericata were obtained which failed to emerge and were kept for 

 a number of weeks in a warm room in damp sand. At the end 

 of that period they were examined for the possible presence of 

 parasites, but nothing of that nature was found. I have no 

 explanation to offer for this unusual fact. 



On August 8, 1912, a female specimen of L. sericata, IQI2-/, 

 was taken at the garbage scow, Boston. She laid a number of 

 eggs in less than a week and the larvae soon reached the migration 

 stage. This occurred before August 20. They were then placed 

 in dry sawdust at room temperature and shortly there appeared 

 thirteen flies, four males and nine females. None of the other 

 larvae pupated and at various times they were removed and 

 examined. They seemed to be in a normal condition and re- 

 acted negatively to light. It was observed that the general tint 

 of the larvae gradually changed from white to light pink due pos- 

 sibly to the exhaustion of nutriment in the fat bodies. On 

 October 23 they were all very pink but were still active although 

 they had been in dry sawdust at room temperature for at least 

 two months. At this time they were placed in damp sand and 

 pupae were soon formed from which thirteen males and eleven 

 females emerged from November n to November 19. On 

 November 20 and 21, several more flies emerged but unfor- 

 tunately these were not counted. By December 4 the sand had 

 dried somewhat and an examination showed nine larvae remain- 

 ing. The sand was dampened and on December 24, two flies 

 emerged; on December 31, two more; and on January 3, one 

 fly came out. This was the last of the lot, the other four having 

 been killed on December 25 and studied for the presence of 

 parasites, such as bacteria, etc. Nothing of this sort was found, 

 however. 



