262 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



jurious there are two generations a year, but further south there 

 is evidence of at least a partial, if not complete, third generation, 

 and in the northern range of the species there is but one gen- 

 eration a year. 



Natural Enemies. One of the chief agencies to prevent the 

 excessive multiplication of this pest is the weather. Thus, Pro- 

 fessor Otto Lugger records that in Minnesota, late in the fall 

 of 1894, the beetles were lured from their winter quarters by a 

 few warm days, and most of them subsequently perished from 

 hunger or frost. In addition to this during the late summer of 

 1894 there was an excessive drouth, so that but few of the second 

 brood matured. Thus in 1895 there were very few of the in- 

 sects to be seen. 



Among the birds, the common crow, the red-breasted gros- 

 beak, and turkeys often feed upon this pest to a considerable 

 extent. 



Probably the most destructive insect-parasite of the larvae is a 

 Tachinid-fly known to science as Lydella doryphoroe Riley, which 



rather closely resembles the com- 

 mon house fly, both in size and 

 color. A single egg is laid on a 

 potato bug and from it hatches a 

 small, footless maggot which bur- 

 rows inside the bug. When the 

 larva enters the earth, the effect 

 of the maggot's work becomes ap- 

 parent, and instead of transform- 



. _ . ing to a pupa and beetle, it shrivels 

 FIG. 224. Tachmid parasite of Col- 

 orado potato-beetle (Lydella dory- up and dies; but the maggot itself 

 phora Ril.). (After Riley.) contracts into a hard, brown pupa, 



from which the fly eventually emerges. Thus in 1868, when 

 first noted by Dr. C. V. Riley, he asserted that in Missouri fully 

 10 per cent of the second brood and one-half of the third were 

 destroyed by this parasite. 



Many of our common lady-bird beetles and their larvae check 

 the pest by feeding upon the eggs. Several predaceous bugs, par- 

 ticularly the spined soldier-bug (Podisus spinosus Dall.) (Fig. 223) 

 are of value in destroying the larvae, into which they thrust their 

 short, powerful beaks, and then suck out the juices of the body, 



