ANATOMY AND PHYSIOLOGY 



81 



FIG. 99. 



Stinging hair of a caterpillar, 

 Gastropacha. c, cuticula; g, 

 gland cell; h, hair; hy, hypo- 

 dermis. After CLAUS. 



extremity of the hair. Bulbous tenent hairs occur also on the 

 tarsi of Collembola, Aphididae and other insects. 



Nettling hairs or spines clothe the 

 caterpillars of certain Saturniidae 

 (Aittomeris) , Liparidae, etc. These 

 spines (Fig 1 . 99), which are sharp, 

 brittle and filled with poison, break 

 to pieces when the insect is handled 

 and cause a cutaneous irritation 

 much like that made by nettles. In 

 Lagoa crispata (Fig. 100) the irri- 

 tating fluid is secreted, as is usual, 

 by several large hypodermal cells 

 at the base of each spine. These 

 irritating hairs protect their pos- 

 sessors from almost all birds except 

 cuckoos. 



Repellent Glands. The various 

 offensive fluids emitted by insects 



are also a highly effective means of defence against birds 

 and other insectivorous vertebrates as well as against preda- 

 ceous insects. The blood itself serves 

 as a repellent fluid in the oil-beetles 

 (Meloidae) and Coccinellidae, issuing as 

 a yellow fluid from a pore at the end 

 of the femur. The blood of Meloidae 

 (one species of which is still used me- 

 dicinally under the name of " Spanish 

 Fly ") contains cantharidine, an ex- 

 tremely caustic substance, which is an 

 almost perfect protection against birds, 

 reptiles and predaceous insects. Coccinel- 

 lidae and Lampyridae are similarly exempt 

 from attack. Larvae of Cimbex when 

 disturbed squirt jets of a watery fluid 

 from glands opening above the spiracles. Many Carabidae 

 eject a pungent and often corrosive fluid from a pair of anal 

 7 



FIG. 100. 



Stinging spines of a 

 caterpillar, Lagoa cris- 

 pata. After PACKARD. 



