4 CIRCULAR 18, U. S. DEPARTMENT OF AGEICULTUEE 



females have been observed ovipositing on the same egg mass at 

 the same time. They appear to be able to determine to some extent 

 which eggs have been parasitized, since females have been observed 

 to fly away without attempting to oviposit after examining an egg 

 mass upon which several females had previously oviposited. No 

 egg mass has ever been found to be completely parasitized, since 

 some tabanid larvae have hatched from each of the several hundred 

 masses collected. In collected egg masses, 93 per cent is the highest 

 percentage of parasitization of any single mass; the average in 

 any considerable number of masses has never been above 60 per cent, 

 as determined by the number of adult parasites emerging and the 

 number of tabanid larvae hatching. (Fig. 2.) 



Fig. 2. — Mass of eggs of Tabanus hi/alinipennis (viewed 

 from above), showing emergence holes of the parasite. 

 These egg massses are usually about one-half of an 

 inch across 



There are not enough data at hand to determine the number of 

 young a single female Phanurus is capable of producing. From 

 three masses of fly eggs which had been attacked by a collected 

 female parasite, 114 adult parasites have been reared. 



The males usually die within a few hours after copulation and 

 the females die soon after oviposition has been completed. Adults 

 have rarely ever lived longer than two days in the breeding jars and 

 none for more than five days. The adults have been supplied with 

 water, sweets, and flowers in the breeding jars, but have never been 

 observed to feed. They have bred quite freely in 4-ounce tumblers, 

 pint Mason jars, and smaller shell vials. It has been found advan- 

 tageous to introduce moisture into the jars by placing clean moist 



