108 U.S. NATIONAL MUSEUM BULLETIN 256 



can be determined by the hard black sap exudation from the affected 

 areas. Where the insect is abundant, several cells may occur in one 

 cladode, which may rot through the action of plant diseases that 

 extend the injuries caused by the weevil larvae. Under these circum- 

 stances G. nobilis is capable of bringing about considerable damage 

 to prickly pear plants. 



Gerstaeckeria basalts (LeConte) 



Adults reared from Opuntia tortispina at Littleton, Colorado, were 

 given this determination. 



Gerstaeckeria cactophaga (Pierce) 



This weevil appears to be confined to the lower Rio Grande Valley 

 of Texas, where adults have been collected on prickly pear at Kings- 

 ville and in small numbers at Brownsville. 



Gerstaeckeria elegans Fisher 



The original description was made from a single specimen taken on 

 prickly pear at San Luis Potosi, Mexico, in June 1927. 



Gerstaeckeria unicolor (Fisher) 



Described in 1928 from an adult collected at San Luis Potosi, Mexico, 

 this weevil appears to be common in the general neighborhood 

 of the type locality, where it is found in company with G. doddi. In 

 April and May 1930 larvae were extremely abundant and, assisted 

 by Syrphid larvae and plant diseases in the rotting tissue, were causing 

 considerable damage to the more succulent forms of prickly pear such 

 as Opuntia robusta. Undetermined Gerstaeckeria adults from Saltillo, 

 Zacatecas, and Mexico City, Mexico, may represent this species. 



Gerstaeckeria cuhaecola (Fisher) 



This weevil was described in 1928 from several adults collected on 

 Opuntia dillenii at Santiago, Cuba, in December 1926. 



Gerstaeckeria insulana (Fisher) 



This weevil was described in 1928 from material taken on Opuntia 

 dillenii at Port-au-Prince, Haiti, in January 1927. In the same month 

 an emerged pupa and typical feeding punctures of adult Gerstaeckeria. 

 were observed on 0. antillana at Azua, Dominican Republic, Hispaniola. 



