22 PRINCIPAL CACTUS INSECTS OF UNITED STATES. 



growth of the plants. At the end of the season there are no more 

 joints than there were the year before. 



A hymenopterous parasite of this species, Eiphosoma texana Cres- 

 son, has been reared. It does not appear, however, to be sufficiently 

 abundant to exert much control over the species. 



CONTROL. 



Mr. J. D. Mitchell has found by experiments performed at Vic- 

 toria, Tex., that it is not difficult to control the species by the early 

 application of powdered arsenate of lead. As soon as damage be- 

 comes evident in the spring the new growth should be dusted care- 

 fully with this arsenical. In this way the majority of the first 

 brood will be destro} r ed. Some of the joints infested at that time will 

 recover and there will be little injury from the following broods. 

 The early application of the arsenical is very important on account 

 of the formation of the protective web soon after the larvse have 

 begun work. If the first brood should not be reached in time every 

 effort should be made toward applying the poison in ample time for 

 the second brood. 



In the case of small experimental plantings the use of the gasoline 



torch will furnish an economical means of control. In other cases 



the cutting off and burning of the early infested joints will answer 



the same purpose. 



Disonycha varicornis Horn. 1 



Disonycha varicornis Horn is a flea-beetle about 7 mm. in length. 

 It is of conspicuous appearance on account of the brilliant polished 

 blue of the elytra. The head and thorax are yellow; the under parts 

 dark brown. So far as known this insect is restricted to Opuntia 

 leptocaulis and Opuntia arborescens. It has never been found on the 

 broad-leafed species of the genus Opuntia. It is observed frequently 

 on its host plants in the adult and immature stages. The larvae feed 

 on the surface of the plants without any protective covering what- 

 ever. (PI. IV.) Frequently they occur in such numbers as to cause 

 the death of the plants. As it happens that the cacti attacked by this 

 insect are not of any special economic importance, it is unnecessary to 

 give further attention to the species. 



Stylopidea picta Uhler. 2 



Stylopidea picta Uhler is a slender hemipterous insect about 6.5 

 mm. long. The head and thorax are bright crimson and the wing 

 covers slate color but with narrow yellowish borders. The eyes are 



1 Order Coleoptera, Family Chrysomelidoe, Subfamily Halticinse. 

 - Order Hemiptera, Family Capsidse. 



