INTERRELATIONS OF INSECTS 343 



Atemcles cava occurs in the nests of Formica rufa, and is much 

 prized by this ant on account of the fluid which the beetle 

 secretes from glandular hairs on the sides of the abdomen. 

 The beetle Claviger has at the base of each elytron a tuft 

 of hairs, which the ants lick persistently. This beetle is blind 



Atemeles emarginatus being fed by an ant, Myrmica scabrinodis. After WASMANN. 



and appears to be incapable of feeding itself; for when de- 

 prived of ant-assistance it dies, even though surrounded by 

 food. These cases of symbiosis, or mutual benefit, are well 

 authenticated. 



Visitors. Many myrmecophilous insects are not restricted 

 to ants' nests, but are free to enter or to leave. This is true of 

 such Staphylinidae as visit formicaries simply for shelter or to 

 feed upon detritus, and these visitors are treated with indif- 

 ference by the ants. 



Intruders. Not so, however, with species that are inimical 

 to the interests of the ants, such as many species of Staphy- 

 linidse and Histeridae, which steal food from the ants, kill 

 them or devour their larvae or pupae at every opportunity. 

 The ants are hostile to these marauders, though the latter often 

 escape through their agility or else rely upon their armor for 

 protection. Quedius brevis and Myrmedonia, as Schwarz 

 observes, are soft-bodied forms which remain beside the walls 

 of the galleries or near the entrance of a nest and attack soli- 

 tary ants ; while Hetcerius, which mixes with the ants, is pro- 



