Civic Cooperation 131 



site of beneficial. It is only due to the protective color 

 scheme of the caterpillars that some escape from the fate 

 of becoming food for the parasite brood. 



Besides these parasitic insects, there are others which 

 eat the depredators directly. The interesting Mantis, Rear- 

 horse or Walking-stick, is one of these; ants and spiders are 

 others, which, however, even more than the birds, do not 

 make much distinction between friend and foe. The 

 larvae of the tiger-beetles {Cicindelida) and "ground-beetles" 

 (Carabida;), on the other hand, with some other beetle larvae, 

 are more useful caterpillar hunters, because feeding on 

 specific injurious insects. Among the most important are 

 the "lady-bugs" {Coccinella) , whose small-headed, long- 

 legged larvae, often prettily colored, prey especially on plant- 

 lice and scale-insects. Quite a number of other friends 

 could be mentioned. 



While it is well to know these friends, it is in most cases 

 impossible to rely on them for much practical help, espe- 

 cially in street trees, where wdiolesale methods of warfare 

 become necessary, and no fine distinctions can be drawn, 

 i.e., where poison is used, which generally kills both friend 

 and foe. 



Civic Cooperation. In the city, unbalanced conditions 

 have been created by man and have been maintained so 

 long that insect pests have the best chance for growing con- 

 tinuously worse, unless special effort is made to keep them 

 in check. Theoretically, it would be possible by a supreme 

 effort to get rid of aU these pests, and then by moderate 

 attention to keep them subdued. Practically, the condi- 

 tions for securing this result are rarely attainable; especially 

 when private owners do not fall in line with the efforts at 

 extermination. Wliile much may be done by private asso- 

 ciated effort, there are always some persons antagonistic or 



