240 



THE STUDY OF INSECTS 



able exceptions to what are usually the habits of members of this order is 

 presented by the larva of this species. This larva is able to descend into 

 water and remain there for a long time. 



The young larvae of this species have not been observed; doubtless 

 they are leaf-miners. The older larvae live in the leaf-stalks of the pond- 

 lily, a single larva in a leaf -stalk. The larva bores a hole from the upper 

 side of the leaf into the petiole, which it tunnels in some instances to the 

 depth of two feet or more below the surface of the water. This necessi- 

 tates its remaining below the surface of the water while feeding. The 

 tracheae of these larvae are unusually large, and we believe that they 

 serve as reservoirs of air for the use of the insect while under water. 

 The form of the hind end of the larva has also been modified, so as to fit 

 it for the peculiar life of the insect. The last segment appears as if the 

 dorsal half had been cut away; and in the dorsal part of the hind end of 

 the next to the last segment, which, on account of the peculiar shape of 

 the last segment, is free, there open a pair of spiracles much larger than 

 those on the other segments. When not feeding the larva rests at the 

 upper end of its burrow, with the segment bearing these large spiracles 

 projecting from the water. 



The Armyworms 



Not all of the moths in this group have caterpillars that are gregarious 

 and march over the ground in great numbers. Some are simply cut- 

 worms with the habits of ordinary cutworms although most of these pests 

 are found in the next group. 



The armyworm, Cirpkis unipuncta. — The armyworm is so called 

 because it frequently appears in great numbers, and, after destroying the 



vegetation in the field where the eggs are 

 laid, marches like an army to other fields. 

 It is, however, a simple cutworm in most 

 years. This insect occurs throughout the 

 United States east of the Rocky Moun- 

 tains and is present every year; but it 

 attracts attention only when it appears 

 in great numbers. The larva is from if 

 to 2 inches long when full-grown and is 

 striped with black, yellow, and green. 

 The adult is of a dull brown color, 

 marked in the center of each fore wing 

 with a distinct white spot (Fig. 421). In 

 seasons of serious outbreak of this pest 

 it usually appears first in limited areas, 

 in meadows or pastures. 



The green fruit-worms. — There are three species, Xyllna antennaria, 

 X. laiicineria, and X. grotei, the larvae of which attack the fruit of the 

 apple, pear, peach and plum. The caterpillars are yellowish-green or 

 apple-green in color, about if inches long and much alike in appearance. 

 They eat cavities in the sides of the fruit, which scar and deform the 

 apples and pears especially. 



The moths of the three species are gray in color, very similar in ap- 

 pearance and with a wing-expanse of about if inches. 



Fig. 421. — Cirphis unipuncta. 



