30 ■ Riley — Presidential Address. 



to the subject of myrmecophilous insects alone. Ants are as a 

 rule hostile to every other living thing, except such as the plant- 

 lice, which furnish them with desii'ed sweets. They fiercely 

 resent any intrusion into their nests, and often attack and kill 

 their own kind if belonging to another colony. It is there- 

 fore remarkable that careful examination of almost any formi- 

 cary will reveal the presence of a multitude of different in- 

 sects which appear to live peaceably in the company of the legiti- 

 mate inhabitants. A mere list of these myrmecophilous insects 

 would be of little interest. The species comprise, first, those 

 which, in the larva and pupa states, live among the ants ; secondly, 

 accidental visitors, not confined to ants' nests; and, thirdly, the 

 true myrmecophilous species, i. e., those which in the imago state, 

 and so far as known in the adolescent states also, are exclusively 

 found in ants' nests and depend for their existence on the ants. 

 In some species of the second category we already find a tendency 

 to simulate in color the ant itself, or the surroundings of the 

 formicary; but the true myrmecophilae, or species of the third 

 class, often mimic m the most remarkable manner the host upon 

 which they depend. Some of these myrmecophilous sjiecies are 

 mere scavengers, and feed upon the offal, of an animal or vegetal 

 nature, which is always found abundantly in the nests of ants. 

 They are endured with indifference by the ants, because they are 

 useful in an iudirect way, helping in the performance of a duty 

 which would otherwise have to be performed by the ants them- 

 selves. Another group is present as marauders, living in the 

 nests for the purpose of stealing and devouring the ants' eggs, 

 larva? or pupa?, whenever a chance offers. To this group be- 

 long the various Histerida?, a Coleopterous family in which the 

 species are so constructed that it is impossible for the ants to ad- 

 vantageously attack them. In the third grouj) we find species 

 characterized by sweet secretions, from which the ants derive 

 benefit. In some cases, as in the black, clumsy beetles of the 

 genus Cremastochilus, the insects are not absolutely confined to 

 the formicary, though they are always developed there. Fre- 

 quently in the perfect state they endeavor to escape, and it is curi- 

 ous to note the strategy which the ants employ to prevent the de- 

 parture of these inquilines or guests from which they obtain the 

 coveted sweet. In such cases, as in the well known genus Claviger? 

 and allied genera, the insects are absolutely dependent on the ants. 



