1 82 ENTOMOLOGY 



and more than twenty species prey upon the twig-like geometrid larvae; 

 while the weevils that look like particles of soil, and the green-striped 

 caterpillars that assimilate with the surrounding foliage are constantly 

 to be found in the stomachs of birds. 



After all, however, protective resemblance may be regarded as ad- 

 vantageous upon the whole, even if it is ineffectual in thousands of in- 

 stances. An adaptation may be successful even if it does fall short of 

 perfection ; and it should be borne in mind that the evolution of protect- 

 ive resemblances among insects has probably been accompanied on the 

 part of birds by an increasing ability to discriminate these insects from 

 their surroundings. 



Warning Coloration. In strong contrast to the protectively 

 colored species, there are many insects which are so vividly colored as 

 to be extremely conspicuous amid their natural surroundings. Such 

 are many Hemiptera (Lygaus, Murgantia), Coleoptera (Necrophorus, 

 Lampyridae, Coccinellidae, Chrysomelidae ) , Hymenoptera (Mutillidae, 

 Vespidae), and numerous caterpillars and butterflies. Conspicuous col- 

 ors, being frequently though not always associated with qualities 

 that render their possessors unpalatable or offensive to birds or other 

 enemies, are advantageous if, by insuring ready recognition, they ex- 

 empt their owners from attack. 



Efficiency of Warning Colors. Owing to much disagreement as 

 to the actual value of " warning" colors, several investigators have made 

 many observations and experiments upon the subject. Tests made by 

 offering various conspicuous insects to birds, lizards, frogs, monkeys and 

 other insectivorous animals have given diverse results, according to 

 circumstances. Thus, one gaudy caterpillar is refused by a certain bird, 

 at once, or else after being tasted, but another and equally showy cater- 

 pillar is eaten without hesitation. Or, an insect at first rejected may at 

 length be accepted under stress of hunger; or a warningly colored form 

 disregarded by some animals is accepted by others. Moreover, some 

 of the experiments with captive insectivorous animals are open to ob- 

 jection on the score of artificiality. 



Nevertheless, from the data now accumulated, there emerge some 

 conclusions of definite value. Frank Finn, whose conclusions are quoted 

 beyond, has found in India that the conspicuous colors of some butter- 

 flies (Danainae, Acrcea viola, Delias eucharis, Papilio aristolochice) are 

 probably effective as "warning" colors. Marshall found in South 

 Africa that mantids, which would devour most kinds of butterflies, in- 

 cluding warningly colored species, refused Acma, which appeared to be 



