636 AN INTRODUCTION TO ENTOMOLOGY 



folded under; and the radius of the hind wing is armed with setae, 

 which hook into this fold. 



The adults fly very swiftly and during the hotter part of the day. 

 They frequent flowers thus increasing their resemblance to bees or 

 to wasps. The larvag are borers, living within the more solid parts 

 of plants. Some species cause serious injury to cultivated plants. 

 More than one hundred species have been found in America north of 

 Mexico. Among the better known species are the following. 



The blackberr}^ crown-borer or the raspberry root-borer, Bembecia 

 margindta. — The larva of this species burrows in the roots and lower 

 part of the canes of blackberries and raspberries, sometimes completely 

 girdling the cane at the crown. 



The peach-tree borer, Synanthedon exitidsa. — This is the most 



important enemy of the peach-tree,except perhaps the San Jose scale 



in the North and the plum curculio in the South. In some parts of 



the country it is difficult to find a peach-tree that is not infested by it. 



The eggs are laid on the bark of the tree near the ground. The larvae 



bore downward in the bark of the trunk just below the surface of the 



ground. Their bun^ows become filled by a gummy secretion of the 



tree. As this oozes out in large masses the presence of the borer is 



easily detected by it. The insect always passes the winter in the larval 



state. When full-grown the larva comes to the surface of the ground 



and makes a cocoon of borings fastened together with silk. The 



perfect insects appear from May till October; 



-^ ^ the date at which most of them appear varies in 



^j^^y^-^^^^^^ different sections of the country. There is a 



^^^StAt^^^ single generation each year. The adults differ 



^^^^jH^^^^ greatly in appearance. The general color of 



|W| both sexes is a glassy steel-blue. In the female 



' V ' (Fig- 779) the fore wings are covered with scales, 



pjg_ jyg-Svtianthedon ^^^ there is a bright orange-colored band on the 



exitiosa , female. abdomen. In the male both pairs of wings are 



nearly free from scales. The usual method of 



fighting this pest is to carefully watch the trees and remove the larvas 



with a knife as soon as discovered. Recently the use of a toxic gas, 



paradichlorobenzene, has been found available on trees six years of 



age and older; and experiments are now being made to determine 



the practicability of its use on younger trees. See U. S. Dept. of 



Agr. Bull. 1 1 69, and later bulletins when pubHshed. 



The Pacific peach-tree borer, Synanthedon opalescens. — On the 

 Pacific Coast there is a peach-tree boier that is distinct from the 

 above, and appears to be an even more serious pest. The larva is 

 more difficult to remove from the tree, as it bores into the solid wood. 

 The female of this species lacks the orange-colored band on the 

 abdomen. 



_ The lesser peach-tree borer, Synanthedon ptctipes. — ^The larvce of 

 this species infest peach, plum, cherry, june-berry, beach-plum, and 

 chestnut. They do not confine their attacks to the crown but more 



