6 BULLETIN 843, IT. S. DEPARTMENT OF AGRICULTURE. 



in their dietary. From an economic standpoint it is a potential pest 

 of the type of the Colorado potato beetle and the boll weevil and it 

 is singular that it has never migrated to any noticeable extent as have 

 those pests, since it is probably capable of extended flights. One 

 reason that may be assigned, for this is its practical limitation to a 

 single food plant, while the potato-feeding insect infests virtually 

 all of the Solanaceae, including the weeds, and is capable of breeding 

 continuously on all species of Solanum and probably on other genera. 

 There is no reason to suppose that this insect may not by flight in- 

 crease its present range materially some time, although not neces- 

 sarily in the near future. Its further dissemination, however, would 

 doubtless be slow and never as rapid as in the case of the compara- 

 tively fleet-winged and more adaptable Colorado potato beetle. The 

 reasons, then, for its failure to have become more widely distributed 

 are : Its limitation to a single food plant and its probable incapacity 

 for protracted flight with the wind. Moreover, it is probably not 

 capable of inhabiting such varied climates as is the Colorado potato 

 beetle, a species which seems to have no respect for life zones but 

 which thrives equally well from subtropical southern Texas to boreal 

 Manitoba. 



In the case of the Colorado potato beetle it can not as yet be defi- 

 nitely stated, as some authors have assumed, that it breeds wherever 

 potatoes are grown, but it is perfectly capable of doing so, and it may 

 be that in the course of time, many years undoubtedly, the bean lady- 

 bird will be distributed wherever its food plant is cultivated. 1 



Another factor which strengthens the belief that the bean ladybird 

 will, in the course of time, become more widely disseminated is its 

 very close relationship, both structurally and biologically, to the 

 squash ladybird (Epilaehna borealis Fab.), which ranges from South 

 America northward through Central America, Mexico, and the An- 

 tilles, along the Mexican and Atlantic seaboard States to Maine and 

 Canada. Obviously the squash-feeding species has a similar tropical 

 origin, beginning farther southward and extending much farther 

 northward. Instead of progressing straight northward it has fol- 

 lowed more nearly the coastal lines and has a totally different distri- 

 bution in the United States, being somewhat restricted to the East 2 

 just as the bean ladybird is restricted to the Middle West. 



The present distribution of this species as outlined in the map 

 would indicate that we may expect its establishment some time in 

 the future in near-by counties in the States of Utah, Wyoming, Ne- 



1 The predacious ladybird Hippodamia convergens Guer. is capable of accommodat- 

 ing itself to practically all climes and countries, with the exception of areas where the 

 temperature is so high or so low that few forms of plant and insect life are able 

 to survive. 



- It occurs, though not as a pest, in certain other regions remote from the region speci- 

 fied, e. g., in Kansas and Arkansas. 



