44 MISCELLANEOUS STUDIES 



All the California species with the exception of Tuberolachnus vimi- 

 nalis (Fonsc.), which lives on willow, are found on conifers Firms 

 sp., Pseudotsuga sp., or Picea, sp. 



Following is a key to the genera, adapted from Del Guercio, Wil- 

 son and Essig. In this key are included not only the California 

 genera but the other three as well, in that an understanding of the 

 characters is thus made easier. 



1. Antennae six-segmented 2 



Antennae five-segmented (fig. 83) Essigella Del Guercio 



2. Stigma exceptionally long, reaching beyond the tip of the wing (fig. 84). 



Longistigma (Wilson) 



Stigma not exceptionally long, not reaching beyond the tip of the wing 



(fig. 85 ) 3 



3. First joint of the hind tarsus much shorter than half the second (fig. 86) .... 4 



First joint of the hind tarsus equal to or slightly longer than half the second 



(fig. 87) -. Eulachnus Del Guercio 



4. Abdomen with horn-like tubercle on median dorsum between the cornicles, 



(Sometimes this cannot be made out in specimens mounted in balsam, but 

 it is always readily discernible in fresh or alcoholic material). 



Tuberolachmus Mordwilko 



Abdomen without horn-like tubercle 5 



5. Bases of first and second discoidal close together; third discoidal often very 



faint; wings slightly if ever clouded (fig. 85) Lachnus Burmeister 



Bases of first and second discoidals not so close together as in Lachnus Burm. ; 



third discoidal plain; wings often darkly clouded Pterochlorus Rondani 



18. Genus Essigella Del Guercio 



Del Guercio, Eev. di patal. veg., vol. 3, p. 328, 1909. Type Lachnus cali- 

 fornicus Essig. 



43. Essigella calif ornica (Essig) 



Figures 3, 5, 83 



Essig, Pom. Jour. Ent., vol. 1, p. 1, 1909. Lachnus (orig. desc.). 



Del Guercio, Pom. Jour. Ent., vol. 1, p. 73, 1909 (translation by C. F. 



Baker of Del Guercio 's paper listed above). 

 Essig, Pom. Jour. Ent., vol. 4, p. 773, 1912 (list). 

 Essig, Pom. Jour. Ent., vol. 4, p. 780, 1912 (desc.). 



Records. Pinus radiata; Claremont, Los Angeles County, and Santa Paula 

 (Essig); Pinus sabiniana, Stanford University, March, 1915; Pinus spp., Stan- 

 ford University, March and April, 1912 (Morrison) ; Ontario, San Bernardino 

 County, January, 1917. 



This curious little aphid, described by Essig from specimens taken 

 in Claremont, Los Angeles County, on Pinus radiata, has since been 

 found in several parts of the state. Wilson has taken it in Oregon 

 on Pseudotsuga taxifolia, and Patch in Maine on Pinus strobus. It 



