702 AN INTRODUCTION TO ENTOMOLOGY 



United States, and infests a great variety of grasses and garden 

 crops. The moth (Fig. 890) is white, marked with yellow and black. 



There are many black dots on 

 the wings, a row of black spots 

 on the back of the abdomen, an- 

 other row on the venter, and two 

 rows on each side. The sexes 

 differ greatly in the ground-color 

 of the wings; in the female, this 

 is white throughout ; in the male. 

 Fig. 890. — Estigmene acrcza. only the Upper surface of the fore 



wings is white, the lower surface 

 of the fore wings and the hind wings above and below being yellow. 

 The number and size of the black spots on the wings vary greatly. 

 There are usually more submarginal spots on the hind wings than 

 represented in our figure. 



The fall web worms, Hyphdntria cunea and Hyphdntria textor. — 

 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. 

 It is a disputed point whether there are one or two species of fall 

 webworms. In the North the adults are all snow-white in color and 

 there is only a single generation annually. This form is the Hyphan- 

 tria 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; which name should be applied to both the northern and 

 southern forms if they prove to be specifically identical, cuneaheing 

 the older specific name. 



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 

 caterpillar reddish brown in the mid- 

 dle and black at either end, which is ..,,,, 

 seen so commonly in the autumn ^'^- ^9i.-Ista ^sabella, larva. 

 and early spring (Fig. 891). The 



extent of the black color varies in different individuals; rarely, es- 

 pecially on the West Coast the body is all brown. In the spring after 



