32 PKINCIPAL CACTUS INSECTS OF UNITED STATES. 



The only cases in which it will be necessary to combat this insect 

 will be those in which the new growth of the plants is affected. The 

 only course to follow is to remove these joints and burn them. 



SPECIES INJURING THE BLOOMS. 



In the category of species injuring the blooms there is only one 

 that is of importance. This is Trichochroiis (Pristoscelis) texanus 

 Le Conte. It is a slender beetle, 3 mm. in length, uniformly oliva- 

 ceous above, highly polished, with reddish legs, the upper surface of 

 the body covered with rather dense growth of short whitish hairs. 

 It has been collected at southwestern Texas and in New Mexico. At 

 Albuquerque, in the latter State, on June 16, Mr. F. C. Pratt found 

 it in such abundance that no blooms without indications of injury 

 were noticed. The great majority of the plants had been fed upon 

 to such an extent that fruiting had ceased. As many as 153 beetles 

 were found in a single bloom. No larvae could be found in the 

 vicinity. It is possible that this species is not at all peculiar to 

 cactus, but is to be found in blooms of various kinds. There was a 

 remarkable absence of flowers on all plants except the Opuntias 

 growing at Albuquerque at the time to which reference has been 

 made. This may account for the concentration of the insects in the 

 blooms of the Opuntias and for the damage accomplished. No simi- 

 lar cases had been observed, in the numerous observations that had 

 been made in Texas. 



Euphoria kernii Haldeman 1 is a very common beetle in cactus 

 blooms in Texas. It is a robust species of very variable color. Some 

 specimens are pure black and all gradations between this form and in- 

 dividuals in which the ground color is yellow, but covered with nar- 

 row black stripes, are to be found. The species seems to feed upon 

 the columns and anthers more than upon the petals. Even where it 

 is so abundant that several individuals are to be found in every 

 bloom no special injury to the plants has been detected. On this 

 account the species is included in the list at the end of this bulletin 

 as one which has no other association with the cactus plant than that 

 it frequents the bloom. 



SPECIES INJURING THE FRUIT. 



Narnia pallidicornis Stal. 



Of the species that injure the fruit, by far the most important are 

 the bugs of the genus Narnia, the most common being N. pallidicornis 

 Stal. 2 The species can be recognized readily. (PI. VII, fig. 4.) It 

 is of a brownish-yellow color, about 15 mm. in length. The posterior 

 femora^ are lengthened, very robust, and covered with heavy black 



1 Order Coleoptera, Family Scarabseidae. 2 Order Hemiptera, Family Coreidae. 



