11 



INSECT ENEMIES. 



Of the invertebrate enemies of the chinch bug the same may be 

 said as of the frog. The writer has occasionally found a chmch bug 

 containing a species of Mermis, or "hair snake." Occasionally, 

 also, ants may be seen dragging these bugs away, while lady-beetles 

 have sometimes been found to devour them, as recorded by Walsh 

 and Forbes. Perhaps the worst insect enemies of the chinch bug 

 are to be found among its comparatively near relatives — the insidious 

 flower bug {Triplileps insidiosus Say), (Anthocoris fseudo-cJiinclie of 

 Fitch's Second Report), and Mihjas cinctus Fab., the latter being 

 reported by Thomas as the most efficient of the insect enemies of 

 this pest, while Riley found that the former also attacked it. Pro- 

 fessor Forbes ascertained, by exammations of the contents of the 

 stomach of a ground beetle (Agonoderus pallipes Fab.), that one- 

 fifth of the total food of this species was composed of chinch bugs. 

 Shimer and Walsh both claim that lace wing flies (Chrysopa spp.) 

 destroy chinch bugs, and they are doubtless correct. The writer 

 has also very often found dead chinch bugs entangled in spider 

 webs, although whether killed for food or by accident it has been 

 impossible to determine. 



NATURAL CHECKS OTHER THAN ANIMALS. 



There are two natural checks to the increase of the chinch bug 

 other than animal enemies. One of these is vegetable in nature, being 

 a fimgus, the other meteorological, and the interrelation of the two 

 is so close that the former is almost entirely dependent upon the 

 latter. It will at once be seen that the chinch bug, occurring, as it 

 does, from but little north of the equator to nearly a latitude of 50° 

 north and from an elevation of upward of 200 feet above the sea 

 level in the Imperial Valley of southern California to an elevation 

 of upward of 6,000 feet in the mountain regions, must be able to 

 withstand almost every conceivable variation of climatic conditions. 

 (See map, fig. 7.) So far as the influence of temperature is con- 

 cerned, it is only in the most unprotected situations that severe 

 winter weather appears to have much effect in regulating the abun- 

 dance of the pest, although frequent freezing and thawing is known 

 to be fatal to a large percentage of the adults if these occur in exposed 

 situations. Thus temperature may practically be eliminated from 

 consideration. It is also true that the nearly developed insect will 

 witlistand not only the humidity of the Tropics, but continuous 

 drenching rains of more northern latitudes. It is at the time of 

 hatching that the species is most susceptible to meteorological con- 

 ditions. Frequent drenching rains during the hatching season are 

 fatal to the pest almost to the extent of extermination, and it is due 



[Cir. 113] 



