Pomona Journal of Entomology 



Volume I OCTOBER 1909 Number 3 



CONCERNING TWO NEW GENERA AND THREE NEW 

 SPECIES OF APHIDS OF CALIFORNIA 



G. DEL GUERCIO. 



(The following very important paper has recently appeared in the Rivista 

 di Patalogia Vegetale, Pavia, Anno III, n. 20-21, 1909. As this publication is 

 inaccessible to most of our students, I have made a free translation from the 

 Italian of the most important portions, and give it herewith. — Editor.) 



Of the three species of new aphides which are figured and described by 

 E. O. Essig in Pomona Journal of Entomology, I, 1-10, under the names of 

 Lachnus calif ornicus, Rbopalosiphmn violae, and Pemphigus radicicola, two are 

 here referred to new genera under the names Essigella and Trifidaphis Del 

 Guercio. , 



I. Lachnus californicus Essig 



The pine louse resembles in a general way Lachnus agilis Kalt. From 

 that species and all others of this small tribe, californicus differs first of all in 

 the antennae, which are five-articled and not six. By the character of the 

 cubital vein this species resembles more the genus Schizolachnus Mord., than 

 the old genus Lachnus Burm., though this character, drawn from the winged 

 female only, is far less important than one drawn from the tarsi, since the 

 latter is a more comprehensive and constant one. So that the characters as a 

 whole do not correspond either with those of Eulachnus or Lachnclla, which 

 latter, however, have the first tarsal article also distinctly elongate and sub- 

 equal to half of the second article. We are obliged to exclude californicus 

 from either of these genera on account of the nature of the antennae, and I 

 call it Essigella, the name taken from that of the student who has collected 

 and described the species. The new genus is distinguished from others of the 

 Tribe Lacnidi in the following manner: 



