412 AN INTRODUCTION TO ENTOMOLOGY 



measure to the tips of the folded wings from 2.1 mm. to 2.8mm., the 

 hibernating form 3.3 mm. to 4 mm. The general color is light 

 orange to reddish brown, with darker markings. The eggs are laid 

 early in the spring in the creases of the bark, in old leaf-scars, and 

 about the base of the terminal buds. The young n^Tnphs migrate 

 to the axils of the leaf petioles and the stems of the forming fruit; 

 later they spread to the under side of the leaves. They secrete large 

 quantities of honey -dew, upon which a blackish fungus grows; this 

 is often the first indication of the presence of the pest. There are at 

 least four generations each year. Badly infested trees shed their 

 leaves and yoimg fruit in midsummer. In some cases orchards have 

 been so badly injured by this pest that they have been cut down by 

 their owners. 



The methods of control that are recommended are the following : 

 the scraping off of the rough bark from the trunks and larger branches 

 of the trees and burning it, in order to destroy the hibernating adults ; 

 and thorough spraying of the trees with kerosene emulsion or "black 

 leaf 40" tobacco extract when the petals have fallen from the 

 blossoms, in order to destroy the newly hatched nymphs; this spray- 

 ing should be repeated in three or four days; later sprayings are 

 not so effective on account of the protection afforded the insects by 

 the expanded leaves and by their covering of honey-dew. 



A monograph of the North American species of this family has 

 been pubHshed by Crawford ('14). 



SUPERFAMILY APHIDOIDEA 



The Plant-Lice cr Aphids and their Allies 



The plant-lice or aphids are well-known insects; they infest 



nearly all kinds of vegetation in all parts of the countr}'. Our most 



common examples are minute, soft -bodied, 



green insects, with long legs and antenna, 



which appear on various plants in the house 



and in the field. Usually, at least, in each 



species there are both winged and wingless 



forms (Fig. 487). There are many species 



of aphids, nearly all of which are of small 



Fig. 487.— A group of size; some measure less than i mm. in 



aphids. length; and our largest species, only 5 or 



6 mm. 



The body in most species is more or less pear-shaped. The 



winged forms have two pairs of delicate, transparent wrings. These 



are furnished with a few simple or branched veins; but the venation 



is more extended than in either of the two following families. The 



fore wings are larger than the hind wings; and the two wings of 



each side are connected by a small group of hamuli. The wings are 



usually held roof -like when at rest (Fig. 488, ab\ but are laid flat on the 



abdomen in some genera. The beak is four-jointed and varies greatl}- 



