268 



NA TUBAL H1ST0R Y. 



Fig. 262. — Hop-vine moth 

 (Hypsena hunutli). 



Some feed on grass, some affect cucumbers, others bury their eggs in the 

 gooseberry, and still others eat flour and meal. One of these forms, which 

 is a serious pest in the hop-raising regions of central 

 New York, is illustrated here. Not content with doing 

 all the damage it can, it has two broods a year, thus 



doubling the amount of destruction it is capable of 



. . . Wttw/w- y fA'^' 



causing; but, as with most other insects, there is a wii';^" 



periodicity in its abundance, some years there being 

 many of them, while in others they are extremely few. 



As now understood, the word geometry means the science of theorems 

 .and propositions, straight lines, circles, pyramids, spheres, and angles. It 



formerly meant the measurement of the 

 earth's surface ; and so, when mankind 

 wanted a name for the measuring- 

 worms, which loop themselves up and 

 straighten themselves out as if they 

 were going to find out just how many 

 miles it is around our globe, what should 

 be more natural than to call them geom- 

 etrids ? They stretch themselves out as 

 far as possible, and then, taking hold 

 with the legs just behind the head, bring 

 the rest of the body up in a loop, so 

 that the legs at the hinder portion can 

 grasp the surface just behind the ante- 

 rior members, and the body then can be 

 extended as before. Other names are 

 ' inch-worm,' ' span-worm,' and ' loop- 

 worm.' 



The geometrids are all injurious, the 

 amount of injury they do being limited 

 chiefly by the comparative rarity or 

 abundance of the individuals. Prob- 

 ably the best known of all are the 

 canker-worms, which play such havoc 

 with the foliage of our fruit and shade trees. Yet we can easily control 

 these on account of a peculiarity immediately to be described. The larva' 

 let themselves down from the trees by a silken thread, and burrow into 

 the ground, from which they emerge later as perfect insects. The male 

 is winged like most moths, but the female is utterly without wings, and so 

 the only way in which she can get to the leaves to lav her eo-o-s is to 



Fig. 263. — Currant- worm, pupa, and moth which 

 proceeds from the latter. One of the larvse is 

 letting himself down to the earth by a silken 

 thread, previous to pupation. 



