120 U.S. NATIONAL MUSEUM BULLETIN 25 6 



midges issued from the fruit between 7 and 9 a.m., and none emerged 

 after 3 p.m. On the other hand, in March 1927 at Uvalde, emergence 

 occurred after sundown. In experimental work carried out in Aus- 

 tralia, the adults appeared between 4 and 6 p.m. 



No difficulty was experienced in securing mating and oviposition 

 in different types of cages. At Uvalde, both acts were general between 

 9 a.m. and noon in March 1925; but in March 1927 mating and ovi- 

 position were not observed until after sundown, continuing until 

 after dark. In Australian cages, oviposition took place between sun- 

 down and dark, and very occasionally between 5 and 7 a.m. The 

 female crawls over the young bud and selects a position on the side 

 of the bud at about one-half its length. The ovipositor, which is 3 mm. 

 long, is thrust between the small leaflets into the air space in the ovary. 

 About 25 to 30 minute granular eggs are deposited, lightly cemented 

 together in a mass about 0.5 mm. in diameter and resembling a bundle 

 of miniature grapes. Three egg masses have been observed in one fruit. 

 One female may oviposit in several fruit, and two or more may lay 

 in the same bud. The incubation period occupied 5 to 10 days at 

 Uvalde in March. The adults live for 3 to 5 days. 



Judged on larval counts or by the issuing adults, the number of eggs 

 deposited in each bud varies very greatly. In Opuntia lindheimeri the 

 average number of larvae was 40 to 50 per fruit; counts of 70 were not 

 uncommon; and as many as 100 and as few as 2 larvae have been 

 found in individual fruit. At Tehuacan, Mexico, the larvae in fruit of 

 0. hyptiacantha averaged 20, but sometimes not more than 4 or 5 were 

 present. The small fruit of 0. leptocaulis generally produced three midges. 

 In Australia as many as 80 larvae occurred in one fruit of 0. stricta. 



As a rule the affected fruit are definitely yellow and are readily detect- 

 ed. Frequently they are very much swollen, or, if not enlarged, their 

 contour is abnormal in comparison with healthy fruit of the same 

 variety of prickly pear. At Tehuacan, Mexico, infested fruit of 0. 

 hyptiacantha were not appreciably yellow but were much enlarged. 

 In Australia, fruit of 0. stricta were greatly swollen, even to the extent 

 of being three times the size of normal examples; so great an enlarge- 

 ment has not been observed with any of the various prickly pears 

 recorded as host plants in America. 



In Texas attacked fruit of 0. lindheimeri and the closely related 

 0. cacanapa very often assume the character of segments and produce 

 new growth of either segments or fruit. The infested fruit alter in shape 

 to become short and stout or long and narrow. The deve opment of 

 new growth in these fruit commences several weeks after the midges 

 have oviposited in the buds and continues until August or September. 

 More usually segments arise, but fruit production from attacked fruit 



