244 THE STUDY OF INSECTS 



and size of the black spots on the wings vary greatly. There are usually 

 more sub-marginal spots on the hind wings than represented in our 

 figure. 



The fall webworms, Hyphdntria cunea and Hyphdntria tcxtor. — A 

 very common sight in autumn in the North and in midsummer in the 

 South is large ugly webs enclosing branches of fruit or forest trees. These 

 webs are especially common on apple and on ash; but the insects that 

 make them infest more than one hundred kinds of trees. These webs 

 differ from those made by the apple-tree tent-caterpillar in being much 

 lighter in texture and in being extended over all of the leaves fed upon 

 by the colony; and they are also made later in the year. Each web is 

 the residence of a colony of larvae which have hatched from a cluster of 

 eggs laid on a leaf by the parent moth. 



In the North the adults are all snow-white in color and there is only a 

 single generation annually. This form is the Hyphantria textor of those 

 who believe that there are two species. 



In the South, some of the moths have the fore wings thickly studded 

 with dark brown points, some are pure white, and every gradation exists 

 between these two types. Of this southern form there are two generations 

 annually. This form is known as Hyphantria cunea. 



Both forms winter in the pupa state. 



The Isabella tiger-moth, Isia Isabella. — " Hurrying along like a 

 caterpillar in the fall " is a common saying among country people in New 

 England, and probably had its origin in observations made upon the 

 larva of the Isabella tiger-moth. This is the evenly clipped, furry cater- 

 pillar reddish-brown in the middle and black at either end, which is seen 



so commonly in the autumn and early 

 spring (Fig. 427). The extent of the 

 black color varies in different individ- 

 , uals; rarely, the body is all brown. 

 In the spring after feeding for a time 



Fig. 427- -IsiaisabeUa, larva. thg lafya makeg & b lackish-brown CO- 



coon composed largely of its hair. The adult is of a dull grayish tawny- 

 yellow, with a few black dots on the wings, and frequently with the hinder 

 pair tinged with orange-red. On the middle of the back of the abdomen 

 there is a row of about six black dots, and on each side of the body a simi- 

 lar row of dots. 



The yellow-bear, Diacrisia virglnica. — The larva of this species is 

 one of the most common hairy caterpillars found feeding on herbaceous 

 plants. The long yellow hairs with which the body is clothed are uneven 

 in length, some scattered ones being twice as long as the others. The 

 long hairs are nowhere gathered into pencils as with the tussock-cater- 

 pillars. This larva varies greatly in color. The body is most often of a 

 pale yellow or straw color, with a black, more or less interrupted, longi- 

 tudinal line along each side, and a more or less distinct transverse line of 

 the same color between each of the segments. Sometimes the hairs are 

 foxy-red or light brown, and the body brownish or even dark brown. 

 The head and the ends of the feet and fore legs are yellowish, and the 

 venter is dusky. The larva feeds on almost any plant especially on the 

 silk of corn. The cocoon is light, and is composed almost entirely of the 

 hairs of the caterpillar. This insect passes the winter in the pupa state: 

 and it is probable that there are usually two or more broods each year; 



