428 HOUSEHOLD INSECTS 



length. They are short, thick, and fleshy and covered 

 with a dense coat of long, silky brown hairs that project 

 upward and meet to form a ridge or crest along the middle 

 of the back (Plate VIII). Interspersed among these are 

 short, stiff, hollow spines containing a poison secreted by 

 certain cells in the skin at the bases of the spines. When 

 the caterpillar comes in contact with the flesh of a person's 

 body, the tips of the spines penetrate the skin and evidently 

 set free within the wound a poison. The result is a dis- 

 tinct irritation varying in its intensity according to the 

 susceptibility of the person attacked. The structure and 

 effect of nettling hairs are more fully explained in the 

 discussion of the brown-tail moth. 



These caterpillars feed upon blackberry, oak, apple, 

 pear, plum, cherry, and birch. They have been described 

 as appearing like half a hen's egg cut lengthwise and laid 

 flat side down on a leaf. The eggs are bright yellow and 

 laid on end in rows and covered with scales from the moth. 

 The larvae molt five times and spin dense cocoons, in 

 which they pass the winter, the moths appearing in the 

 spring. 



The beautiful io moth, Automeris io, with the con- 

 spicuous spots on the hind wings, also has a nettling cater- 

 pillar. The female moth has an expanse of wings of three 

 to three and one-half inches. The front wings are dull 

 purplish brown and the body, together with the bases of 

 the wings, is covered with long silky hairs. The male is 

 smaller and brighter colored, being of a deep yellow marked 

 with purple-brown. The moths deposit their cream- 

 colored eggs in clusters on corn, cotton, cherry, apple, elm, 

 and oak. These hatch into small caterpillars covered with 

 six rows of branched, black spines. They molt and grow 



