Mar. 3, 1919 



Species of Pegomyia Mining Dock 



235 



Table III — Length of the life of the adults of Pegomyia calyptrata 



Copulation frequently takes place a few hours after the female issues. 

 Flies that had issued during the night were observed in several cases to 

 copulate during the following morning. In order to induce copulation, 

 good results were obtained by placing pairs in 6-dram vials. They could 

 be conveniently watched, and mating took place quite readily. Pairs 

 that were in larger cages usually died before copulation took place. 

 Copulation usually lasted about 40 minutes; in one case it lasted for i 

 hour and 15 minutes. It is still unknown whether a second or later 

 copulations take place. 



The number of eggs laid was obtained only by dissection. About 62 

 ripe eggs were found in a fertilized female. All these are evidently laid 

 during one oviposition period. 



Number of generations. — The writer has been unable to determine 

 accurately the number of generations a year. This is due to the repeated 

 difficulty he experienced in attempts to keep the adults alive for any 

 considerable period of time, as well as the failure to obtain females to 

 oviposit. Only four of many females experimented with laid eggs, and 

 of these none laid more than five eggs. Under such conditions it was 

 impossible to rear the generations through from eggs to adults. How- 

 ever, the number of generations was followed quite accurately by observ- 

 ing conditions in the field and comparing them with conditions under 

 observation at the insectary. 



The various generations overlap one another, and it is impossible to 

 tell, from outside conditions alone, when one ends and the other begins. 

 The terminations of the first generation can be plainly seen. For 

 example, in the spring of 1916 the first flies to issue from puparia kept 

 out of doors over the winter appeared on May 4. The adults continued 

 to issue until May 16. The females began laying soon after emerging; 



