ADAPTIVE COLORATION 199 



ive resemblances among insects has probably been accompanied on the 

 i 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 (Lygceus, Murgantia) , Coleoptera (Necrophorus, 

 Lampyridae, Coccinellidae, Chrysomelidae) , Hymenoptera (Mutillidae, 

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



Iors, 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 accumulatedj 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 aristolochici) 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 Acr&a, which appeared to be 

 not only distasteful but even unwholesome; Acr&a is eaten, however, 

 by the predaceous Asilidae, which feed indiscriminately upon insects 

 for example, beetles, dragon flies and even stinging Hymenoptera. The 

 masterly studies of Marshall and Poulton strongly support the general 

 theory of warning coloration. 



In this country, much important evidence upon the subject has been 

 obtained by Dr. Judd from an extensive examination of the stomach- 

 contents of birds, supplemented by experiments and field observations. 



