428 



AN INTRODUCTION TO ENTOMOLOGY 



pseudogalls the fifth generation is produced; the members of this 

 generation become winged and migrate to witch-hazel in early 

 summer, where they produce the seventh and last generation of the 

 series, the males and oviparous females. These pair and the females 

 soon lay their eggs. Both sexes are wingless. The winged migrants 

 of this species can be distinguished from those of the preceding 

 species by their five-jointed antennae 



Family PHYLLOXERID^ 



The Adelgids and the Phylloxerids 



The members of this family differ from the typical aphids in that 

 both the sexually perfect females and the parthenogenetic forms lay 

 eggs, in lacking vein Ri of the fore wings, and in that the outer part 

 of the stigma is bounded behind by the radial sector (Fig. 500). 



Sc.-R^M^Cu^li^-^ g^ 



Fig. 500. — Wings of Adelges. (From Patch.) 



In this family the cornicles are always wanting; and the males and 

 sexually perfect females are dwarfed and wingless. 



This family includes two subfamilies, which can be separated by 

 the following table. These subfamilies are regarded as distinct 

 families by some writers. 



A. The wingless agamic females excrete a waxy flocculence. The winged forms 

 have five-jointed antennae, the last three segments of which bear each a single 

 sensorium. The wings are held roof-like when at rest. The free part of vein 

 Cu of the fore wings is separate from vein 1st A (Fig. 500). The sexual forms 

 have a beak. The alimentary canal is normal, producing a fluid excrement. 

 The species infest only conifers Adelgin^ 



AA. The wingless agamic females do not secrete a waxy flocculence, but in the 

 genus Phylloxerina they excrete a waxy powder. The winged forms have 

 three-jointed antenna, the second segment of which bears two sensoria. The 

 wings when at rest are laid flat upon the abdomen. The free parts of veins Cu 



