POLYMORPHA^-STAPIIYLINIDAE 



about 9000 species are known, some of which are minute, while 

 scarcely any attain a size of more than an inch in length, our 

 common British black cock-tail, or " devil's coach-horse beetle," 

 Ocypus olens, being amongst the largest. Though the elytra 

 are short, the wings in many forms are as large as those of 

 the majority of beetles ; indeed many Staphylinidae are more 

 apt at taking flight than is usual with Coleoptera ; the wings 

 when not in use are packed away under the short elytra, 

 being transversely folded, and otherwise crumpled, in a com- 

 plicated but orderly manner. It is thought that the power 

 of curling up the abdomen is 

 connected with the packing 

 away of the wings after flight ; 

 but this is not the case : for 

 though the Insect sometimes 

 experiences a difficulty in fold- 

 ing the wings under the elytra 

 after they have been expanded, 

 yet it overcomes this difficulty 

 by slight movements of the base 

 of the abdomen, rather than 

 by touching the wings with 

 the tip. What the value of 

 this exceptional condition of 

 short elytra and corneous dorsal 

 abdominal segments to the 



FIG. 105. Staphylinidae. A, Larva of Phi- 

 present lonthusnitidus. Britain. ( After Schiddte.) 

 B, Ocypus olens, Britain ; C, tip of abdo- 

 men, of O. olens with stink-vessels-. 



Insect may be is at 

 quite mysterious. The habits 

 of the members of the family 

 are very varied ; many run with great activity ; the food is 

 very often small Insects, living or dead; a great many are 

 found in fungi of various kinds, and perhaps eat them. It is 

 in this family that we meet with some of the most remarkable 

 cases of symbiosis, i.e. lives of two kinds of creatures mutually 

 accommodated with good will. The relations between the 

 Staphylinidae of the genera Atemeles and Lomechusa, and certain 

 ants, in the habitations of which they dwell, are very interesting. 

 The beetles are never found out of the ants' nests, or at any rate 

 not very far from them. The most friendly relations exist between 

 them and the ants : they have patches of yellow hairs, and these 

 VOL. vi Q 



