SPECIES ATTACKING JOINTS INTERNALLY. 



31 



The four species described are true cactus insects, being dependent 

 upon the plant for food and places for breeding. Although only- 

 four species have been discovered breeding in cactus, it is likely that 

 upon investigation other species of the genus will be found to injure 

 it. The genus contains 22 species, of which 11 are found in the 

 United States and the remainder in Mexico. 



It is doubtful whether it will ever be necessary to resort to control 

 measures in the case of any of the species of Gerstseckeria. If con- 

 trol should become necessary, it would be extremely difficult on ac- 

 count of the fact that the immature stages are passed beneath the 

 surface of the joint. No remedy except the removal of the infested 

 joints can be suggested. 



Marmara opuntiella Busck. 1 



The tineid moth. Marmara opuntiella Busck (fig. 4), deposits its 

 eggs just beneath the epidermis of the leaves of Opuntia. The first 



m^TrC^^^^m 





Fig. 4. — A cactus insect, Marmara opuntiella: <i. Adult : b, larva; c, eggs and pupal case. 



Enlarged. (Original, i 



indication of injury is a slight elevation of the epidermis above the 

 gallery which the larvae have begun to excavate. The first attack 

 (PI. VI) is generally near the base of the joint. Later the epidermis 

 above the galleries becomes white and the galleries may cover the 

 entire surface of the joint. This is certain to be the case where sev- 

 eral eggs are deposited in one joint. A gummy exudation appears 

 and the whole surface of the joint becomes covered with a yellownsh 

 secretion that conceals the mines. The larva? work immediately 

 beneath the epidermis and never penetrate the interior of the joint. 

 On this account they have little effeci upon the growth of the plant. 

 Only on rare occasions when the attack has been directed against the 

 new growth does the joint fall to the ground. The species is widely 

 distributed in Texas, having been taken from New Braunfels south- 

 ward to Brownsville. 



1 Order Lepidoptera, Family Tineidae. 



