HOST KELATIONS OF COMPSILURA CONCINNATA 7 



has it given forth Compsilura. Whatever may be its status as a sum- 

 mer host, it is certainly of minor importance as a hibernating one. 



There is only one record of an abundance of Papilio polyxenes. 

 Usually the larvae are solitary. A great many adults have been reared 

 and Compsilura often secured. The collections indicate a partial 

 second generation, the insects passing the winter as chrysalids. 

 P. troilus is seldom of economic importance and is similar in its life 

 history to P. polyxenes. Undoubtedly it is common, although collec- 

 tions have been received only during the last three years. It is one 

 of the most acceptable hosts; and, were it not restricted to certain 

 food plants (sassafras and Lindera), it would rank high in impor- 

 tance as a hibernating host. Collections totaling 65 larvae made dur- 

 ing September, 1920, gave 24 adult Compsilura the following 

 spring — a record for hibernation far ahead of any other met in the 

 writers' studies. As many as five individuals have been known to 

 winter successfully in one host chrysalid. 



Apatela furcifera and A. brumosa are strictly solitary and, al- 

 though never plentiful, seem constant in their appearance each year. 



There is great difficulty in satisfactorily determining the species 

 of the genus Thanaos, and so the larvae have been separated according 

 to their food plant- It is only those species which feed upon the oaks 

 that are of immediate concern. Adults, identified as T . juvenalis 

 Fab. and T. horatius Scud, and Burg., were reared from these collec- 

 tions. Some of the species have at least a partial second generation 

 and the larvae are found in the field from July to October. Though 

 solitary, they are sometimes found in abundance. Compsilura has 

 been reared from larvae collected in August, the parasite issuing a 

 few weeks later and also on two occasions from larvae collected in the 

 fall, the parasite issuing the following spring. The host value of the 

 entire group is uncertain. 



GENERATIONS OF COMPSILURA 



As will be seen by reference to Table 2, the time of emergence of 

 Compsilura varies from year to year. Doubtless this factor is greatly 

 influenced by climatic and environmental conditions as would also be 

 the number of generations. However, in order to estimate the field 

 appearance of the various generations, there must first be chosen 

 what seems to be an average year. For this purpose, let us say that 

 the period of emergence for the first generation extends from May 

 24 to June 15. Allowing an 18-day longevity period for the adults, 4 

 this would extend the range of the first generation to July 3. Grant- 

 ing 30 days for a second generation and a longevity of 18 days for 

 the adult, we would then have flies of the second generation from 

 June 24 to August 22. At the time of the first emergence of the 

 individuals of the second generation, there are still many adults of 

 the first generation in the field. Thirty days later (July 24) adults 

 of the third generation would begin to appear, and it is perfectly 

 possible that stragglers of this generation would be found as late 

 as October. During an extremely mild season a partial fourth gen- 

 eration, the adults of which would issue August 24 and later, is not 

 at all unlikely. 



* Culver (2, p. 16) found that the fertilized females would live for an average of 18 days 

 in confinement and that mated males would live a few days longer. Unmated flies lived 

 but a short time. 



