INSECTS. 



253 



which really is not a locust at all. It derives its common name from the 

 fact that its swarms make their appearance once in seventeen years. The 

 larvae spend this long time underneath the earth, where they feed upon tin- 

 roots of various trees. At last the time comes for emergence, and then 

 the clumsy-looking but rather active pupae bore up out of the soil 

 make their way to trees, where, clinging to the hark, they undergo the lasl 

 molt, and the perfect insect appears. 



There are two distinct broods of the seventeen-year locust, in one of 

 which the locusts emerge once in seventeen years, while in the other the 

 period has been changed to thirteen years. 

 In different regions each brood has its 

 own times of emergence, and hence we 

 may hear of swarms of these insects 

 almost every year in some part of the 

 country ; but in each region the seventeen 

 or thirteen year period is invariable. These 

 insects do considerable damage, not only 

 when in the preparatory stages by gnaw- 

 ing the roots of trees and shrubs, but as 

 adults by their punctures of the bark, and 

 by the way in which they deposit their 

 eggs. They select small branches of the 

 trees, and with their ovipositor they bore 

 into them to the pith, and then deposit their eggs in the hole thus made. 

 The branches thus injured (which may contain as many as fifty packet 

 eggs) soon die and are broken off by the wind. In this way the young, as 

 soon as they hatch, are able to immediately burrow into the earth ; but 

 occasionally it occurs that the branch does not break off. and then the 

 larvae are said to precipitate themselves to the ground, and then to make 

 their way to some tender and succulent root. 



The lantern-flies and candle-flies are tropical species occurring in both 

 hemispheres. They are peculiar in shape, the front of the head being pro- 

 longed into a long horn, or 'lantern,' like that shown near the centre of the 

 plate opposite page 250. By some this lantern is said to be phosphi 

 cent, while others deny it any luminous properties, and say thai these 

 insects fly only in the day-time, when any such light would be useli $s 



Every one has noticed on the grass of our fields and lawns small ma 

 of what is apparently spittle, and no doubt the question often arises, How 

 came it there when there is not a trace of a person having been near ? 1 he 

 answer is, that the mass is not spittle at all, but is the product of a little 

 larval bug which sits fastened to the grass, with its beak perforating the 



Fig. 238. — Earthen tubes made by the seven 

 teen-year locust just before assuming the 

 adult condition. 



