200 ENTOMOLOGY 



Judd says that the harlequin cabbage bug (Murgantia histrionica) and 

 other large showy bugs are usually avoided by birds; that the showy, 

 ill-flavored lady-beetles (Coccinellidae) and Chrysomelidae such as the 

 elm leaf beetle, Diabrotica, and Leptinotarsa (Doryphora), possess 

 comparative immunity from birds; and that Macrodactylus, Chauliog- 

 nathus and Cyllene are highly exempt from attack. Such cases, he- 

 adds, are comparatively few among insects, however, and in general, 

 warning colors are effective against some enemies but ineffective against 

 others. 



Generally speaking, hairs, stings and other protective devices are 

 accompanied by conspicuous colors though there are many exceptions 

 to this rule. These warning colors nevertheless fail to accomplish their 

 supposed purpose in the following instances, given by Judd. Taking in- 

 sects that are thought to be protected by an offensive odor or a dis- 

 agreeable taste: Heteroptera in general are eaten by all insectivorous 

 birds, the squash bug by hawks and the pentatomids by many birds; 

 among Carabidae with their irritating fluids, Harpalus caliginosus and 

 pennsylvanicus are food for the crow, catbird, robin and six others; 

 Carabus and Calosoma^&re relished by crows and blackbirds; Silphidae 

 are taken by the crow, loggerhead shrike and kingbird ; and Leptinotarsa 

 decemlineata is eaten by at least six kinds of birds : wood thrush, rose- 

 breasted grosbeak, quail, crow, cuckoo and catbird. Of hairy and spiny 

 caterpillars, Arctiidae are eaten by the robin, bluebird, catbird, cuckoo 

 and others; the larvae of the gipsy moth are food for the blue-jay, robin, 

 chickadee, Baltimore oriole and many others [thirty-one birds, in Massa- 

 chusetts]; and the spiny caterpillars of Vanessa antiopa are taken by 

 cuckoos and orioles. Of stinging Hymenoptera, bumblebees are eaten 

 by the bluebird, blue-jay and two flycatchers; the honey bee, by the 

 wood pewee, phcebe, olive-sided flycatcher and kingbird; Andrena by 

 many birds, and Vespa and Polistes by the red-bellied woodpecker, king- 

 bird, and yellow-bellied flycatcher. 



These facts by no means invalidate the general theory, but they do 

 show that ''disagreeable" qualities and their associated color signals 

 are of little or no avail against some enemies. The weight of evidence 

 favors the theory of warning coloration in a qualified form. While con- 

 spicuous colors do not always exempt their owners from destruction, 

 they frequently do so, by advertising disagreeable attributes of one sort 

 or another. 



The evolution of warning coloration is explained by natural selec- 

 tion; in fact, we have no other theory to account for it. The colors 



