CACTUS-FEEDING INSECTS AND MITES 107 



to 2 inches in diameter, in the disk of the upper segments. The tissue 

 of the affected area is destroyed, producing a "shot-hole" effect. Where 

 the species is common, several separate cells may occur in one cladode; 

 each cell contains one larva, which pupates in a small hard cocoon 

 within the cavity. 



In addition to the usual mode of development within the segments, 

 breeding may take place in the Opuntia flowers, a habit that has not 

 been observed among other species of Gerstaeckeria, In late April 1925 

 in the foothills country west of Del Rio, Texas, many adults were feeding 

 on the buds and unopened flowers of various kinds of prickly pear. 

 Larvae were very abundant within the flower heads, devouring the 

 stamens, style, and fleshy base of the petals; they pupated within the 

 dead corolla; very occasionally the larvae penetrated into the fruit. No 

 instance was recorded of the presence of larvae in flower heads that had 

 opened. The injured buds were unable to open, and the fruits were 

 rendered sterile. In some areas fully 75 percent of the flower heads 

 contained larvae or pupae. Collected material produced adults in May 

 and June. A similar infestation was noticed in the same locality in mid- 

 April 1928, when the adults were extremely numerous. 



A chalcid parasite, Tetrastichus gerstaeckeriae, has been reared from 

 the cocoons. 



Gerstaeckeria huhhardi (LeConte) 



This is a Florida species that is widely distributed in that state, having 

 been taken at Jacksonville, Gainesville, Palatka, New Smyrna, Miami, 

 and other localities. Adults have been observed practically throughout 

 the year. The larvae live in individual cells near the base of Opuntia 

 dillenii, 0. lata, 0. austrina, and other Platyopuntias. 



Gerstaeckeria nobilis (LeConte) 



An inhabitant of the more coastward areas of Texas, it is prevalent 

 from Galveston to Brownsville. The most northerly record was made 

 at Dallas, and the most westerly locality is Uvalde, where it is com- 

 paratively rare in comparison with the abundance of G. doddi and 

 G. porosa. Adults have been taken in all months from February to 

 November and have been reported as abundant in February, March, 

 April, May, and October. Probably there are two or three generations 

 annually. 



The larvae live singly in cells on the margin of the upper segments 

 of Opuntia lindheimeri, 0. inermisy and other prickly pears. Their presence 



