2 BULLETIN S26, U. S. DEPARTMENT OF AGRICULTURE. 



The present work was undertaken in the hope of remedying such 

 a condition to some extent at least. The genera of the. world have 

 been studied. Many workers have lent material and the large col- 

 lections of the National Museum and Bureau of Entomology have 

 been drawn upon. In the National Museum collection a large per- 

 centage of types has been available. To the study of preserved 

 material have been added embryological, anatomical, and biological 

 investigations that a better understanding of the natural relationships 

 might be gained. 



Besides many aphidologists in this country and abroad, who have 

 given helpful suggestions and many of whom have read and criticized 

 the manuscript, the writer is indebted to Dr. A. L. Quaintance, of 

 the Bureau of Entomology, for the facilities for conducting many of 

 the biological investigations which to a large extent have laid the 

 foundation for the systematic treatment here given. 



Superfamily APHID OIDEA. 



There appear to be two distinct families in the superfamily Aphi- 

 doidea. These are the Aphididae and the Phylloxeridae. The present 

 paper deals only with the Aphididae. 



Members of the Phylloxeridae differ markedly from forms belong- 

 ing to the Aphididae. In the first place their biologies are quite 

 different in that parthenogenetic oviparous forms occur during the 

 summer. In the Aphididae only the sexed females which are pro- 

 duced in the fall are normally oviparous. 



In structure the two families are separated at once by the formation 

 of the stigma of the forewing. The wing itself seems very little 

 different in an Adelges or Phylloxera from that in some of the special- 

 ized genera of the Aphididae. xln examination of the freshly emerged 

 wing, however, as has been pointed out by Dr. Patch, shows that the 

 stigma in the Phylloxeridae is formed by the radial sector and the 

 stigmal vein is the media. In the Aphididae, on the other hand, 

 the stigma is formed by radius x and the stigmal vein is the radial 

 sector. The two families may thus be separated as follows: 



Key to the Families op the Aphidoidea. 



Summer parthenogenetic oviparous forms produced: Stigma formed by 



the radial sector Phylloxeridae. 



Only sexual oviparous forms produced : Stigma formed by radius x Aphididae. 



A word of explanation in regard to the name Phylloxeridae may 

 be necessary. The genus Chermes was erected by Linnaeus in 1758 

 and in 1862 was replaced by Psylla Geoffroy. For this genus Chermes 

 jicus L. was set as type by Lamarck in 1801. Ficus, therefore, be- 

 comes ipso facto the type of Chermes, and Chermidae the family 

 name of the "jumping plant-lice. ' ; The family name for the aphi- 

 doidean group, therefore, is derived from the genus Phylloxera 

 Boyer (1834). 



