SETM, OR HAIRS, BRISTLES, ETC. 



189 



chitinous integument. The cuticular hair, says Leydig, is in its first 

 condition the secretion of the cellular element of the skin, and a 

 thread-like continuation of the cell-body may rise up through the 

 pore-canal into the centre of the hair, remaining there permanently. 



While the setae are usually simple, they are often branched, 

 plumose, or spinulose, as in larval Hemerobidae, Anthrenus, and 

 Dermestes, the larvae of certain coccinellid beetles, notably Epi- 

 lachlia, and of Cassida, the larvae of arctians, etc., and in bees 

 (Anthophila, Megachile, Osmia, Colletes, Apis, etc.). 



The use of these spinulose, plumose, and twisted hairs in the bees 

 is clearly shown by J. B. Smith, who states that as these insects 

 walk over flowers, the pollen grains adhere to the vestiture, " and 

 this also accounts for the fact, probably noticed by every observant 

 fruit-grower, that bees frequently bury themselves completely in the 

 blossoms, or roll over every part of them. Such insects are after 

 pollen, not honey, and by so rolling about, the pollen grains are 

 brought into contact with and adhere to the surface of the insect." 

 The syrphid flies also pollenize flowers, the pollenizing of chrysan- 

 themums being effected, as Smith states, by Eristalis tenax, and he 

 adds that the body vestiture of the syrphids " is often composed of 

 spurred and branched hairs." (For reference to gathering hairs, see 

 p. 45.) 



Certain remarkable spines occur in limacodid larvae, notably Em- 

 pretia and Adoneta. These we have called caltrops spines, from 



FIG. 213. Cuticular spinnles of larva of Adoneta: a, b, c, d, different forms; e, e', caltrops. 



their resemblance to the caltrops formerly used in repelling the 

 attacks of cavalry. They are largely concerned in producing the 

 poisonous and irritating effects resulting from contact with the cater- 

 pillars of these moths, and are situated in scattered groups near the 

 end of the tubercles. A group of three is represented at Fig. 213, e. 

 They are not firmly embedded in the cuticle, but on the contrary 



