90 THE POPULAR SCIENCE MONTHLY, 



So universal is protective resemblance among insects, in Nicaragua, 

 that Mr. Belt was sure that whenever he found a species provided with 

 special means of defense, others imitating it might be found also, and 

 such indeed was the case invariably. It was noticed that insectivorous 

 birds and mammals did not destroy the fire-flies, which were very 

 abundant, and several insects, especially species of cockroaches, mim- 

 icked them, and in a perfectly fearless manner made themselves con- 

 spicuous, instead of resorting to hiding-places as is the custom of their 

 tribe. 



Those insects which were protected by special means of defense ex- 

 posed themselves without fear, and rather made a display of their qual- 

 ities. With the brilliant Heliconii butterflies, wasps of rich metallic 

 lustre, fire-flies, and many other species, this was very obvious. Per- 

 haps the display of their destructive features is a warning, otherwise 

 they might be destroyed by their natural enemies, although not eaten. 

 Thus a brilliantly-colored frog would come forth fearlessly during the 

 day when others were concealed, and it was at once assumed that no 

 animal would feed upon it ; and, on offering it to fowls and poultry, 

 not one would touch it excepting a duck, which at once threw it down 

 and shook its head with evident dislike. Mr. Belt suggests that the 

 white tail of the skunk laid upon its back makes it conspicuous in the 

 dark, and may be a sort of warning to animals which would do it injury. 



A most interesting instance of mimetic appearance and habit was 

 afiorded by a green, leaf-like locust. This insect would remain per- 

 fectly motionless, exactly resembling a leaf, while its enemies, a species 

 of foraging ants, would run over it, and around it, destroying every 

 insect in their way. The locust might be taken up and dropped again 

 among the ants, still motionless as if dead, thus escaping injury. 



These wonderful features in animal life had previously been studied 

 by Mr. Bates in his researches in the valley of the Amazon, and by 

 Mr. Wallace in several works, and strikingly illustrate the possibility 

 of change in the structure and habits of living creatures. If this 

 were not the case, how surely all types of animals and plants would 

 disappear with the change of their environment ! Mr. Belt calls at- 

 tention to the fact that we are not to understand that one animal's 

 imitating another is a conscious act. Perhaps we know very little of 

 consciousness in these lowly creatures, but it is quite certain that they 

 are conscious of danger, experience fear, and impulse to seek safety. 

 Nor can we doubt that in these may originate those modifications 

 which inaugurate protective resemblances which afterward become so 

 marked. Natural selection is the present and efficient means by which 

 the modified forms are preserved ; those most favorably modified most 

 readily escape destruction, and thus the fittest survive amid inevi- 

 table dangers. 



Perhaps all insects have natural enemies which they fear, and this 

 instinct of self-preservation is active and acute; and it would be 



