GENERIC CLASSIFICATION OF APHIDIDAE. 73 



Genus RHIZOCTONUS Mokrzecky. 

 1895. Rhizoctonus Mokrzecky, Horae. Soc. Ent. Ross., v. 30, p. 438. 



The genus Rhizoctonus was erected for ampelinus Mok. ; a species 

 occurring on the vine. Through the kindness of H. F. Wilson the 

 writer has been able to examine a slide containing alate forms. 

 These, however, are in a very poor condition and it is impossible to 

 determine whether or not cornicles are present. The antennae too 

 are much distorted. This slide seems to indicate, however, that 

 ampelinus is somewhat related to passerinii Sig., an hypothesis which 

 is strengthened by the fact that both species hold the wings flat 

 in repose. The genus, therefore, is placed here with some hesitation. 



Characters.— Antennae of six segments, without secondary sensoria and rather thick. 

 Fore wings with the media simple. Hind wings with both media and cubitus present. 

 Wings held fiat in repose. Cauda and anal plate rounded. 



Type (monotypical), Rhizoctonus ampelinus Mok. 



Tribe MELAPHINI. 



The tribe Melaphim is suggestive both of the Pemphigini and of 

 the Eriosomatini. It is, however, quite distinct from both. The 

 habits more nearly resemble those of the Pemphigini. The tribe 

 is placed here but a study of the sexes may show that it really belongs 

 to the Hormaphidinae. The typical host group is Rhus, and the 

 galls are typically fall galls. 



Characters. — Gall-inhabiting forms. Cornicles absent; antennae of the alate form 

 of five or six segments armed with somewhat oval or linear transverse sensoria. Sexual 

 forms not known. 



The genera may be separated as follows: 



Key to the Genera op the Melaphini. 



1. Both media and cubitus present in the hind wings 2. 



Only the media present in the hind wings Aploneura. 



2. Stigma of four wings pointed on distal portion and extending some distance 



Melaphis. 

 Stigma stopping abruptly on distal extremity 3. 



3. Antennae of five segments Nurudea. 



Antennae of six segments Pemphigella. 



Genus APLONEURA. 



Plate XII, A-E. 



1883. Aploneura Passerini, Aphididae Italicae, p. 78. 



1869. Tetrenema Derbcs, Ann. des Sc. Nat. Zool. (5), v. 11, p. 106. 



1848. Baizongia Rondani, Nuovi Annali delle Scienze Naturali, v. 9, p. 35. 



The genus is distinguished quite easily from related one's by the 

 venation of the hind wings, the relation of the cubitus and anal of the 

 fore wings, and hy the structure of the antennae. The positive determi- 

 nation of the insect of Fabricius may cause Aploneura to fall for 

 Rondani's name. 



