6 NEW CALIFORXIAX APHIDIDAE 



Symydobius^ chrysolepis new species (Figs. 14, 16, 30, 32, 38.) 



The hills in the vicinity of Alpine, San Diego County, are 

 dotted here and there with maul oaks (Quercus chrysolepis), 

 these being quite abundant in the little ravines. In April 1916, 

 the writer noticed a number of ants crawling along a branch of one 

 of these small oaks. This brought his attention to a colonj^ of 

 brownish colored, medium-sized aphids entirely encircling a ter- 

 minal twig and leaf petiole. Further observation showed many 

 of these colonies on many of the trees in the near vicinity. A 

 considerable number of infested twigs were gathered and later 

 examined in the laboratory. Only apterous viviparous females 

 could be found then, but a few days afterward several alates 

 appeared in the colonies in the laboratorj'. There were also a 

 considerable number of Chalcid parasites,'' which had emerged 

 from the apterae. Another examination of tlie trees near Alpine 

 was made in Julj', but no aphids were found. Since then the 

 writer has had no opportunity to make further observations. 

 This species was at first thought to be Symydobius alhisiphus 

 Davis, ^ but, after an examination of specimens sent him, Davis 

 stated that although they were quite similar to specimens of 

 alhisiphus, he considered them as distinct. Below is a table of 

 the major points of difference in the habits and structures of the 

 two species: 



S. alhisiphus Davis S. chrysolepis new species 



Host : Quercus alba (a deciduous oak) Q. chrysolepis (a live oak) 



Occurrence: on under side of leaves on leaf petioles and twigs 



near leaf petioles 

 Alates: Abdomen bro^Ti with a mid- abdomen bro\sTi throughout 



dorsal whitish stripe 



Body, length: ave. 1.16 mm. ave. 1.49 mm. 



!\ntennae, length: ave. .953 mm. ave. 1.428 mm. 



Sensoria: III, 7-8; IV, III, 6-8; IV, 1-2 



5 This species has been placed in the genus Symydobius IVIordwilko only pro- 

 visionally, as it is not typical of the genus. It is so closely related to Symydo- 

 bius alhisiphus Davis, however, that it has been thought best to include it in 

 the same genus as Davis did his species. In the iype species of Symydobius 

 [S. oblongus (Heyden)] the anal plate is very indistinct or barely visible and 

 the third antennal segment of the apterous female bears a few secondary sen- 

 soria. In this species (fig. 38) and in S. alhisiphus Davis the anal plate is 

 distinct and clearly bilobed, and the third antennal segment of the apterous 

 female bears no sensoria. However, it more nearly fits Symydobius than any 

 other genxis known to the writer. 



^ Closterocerus utahensis Crawford var. calijornicus Girault. The writer is 

 indebted to A. B. Gahan and L. O. Howard for the identification of this and 

 other hjTnenopterous parasites of the aphids listed in this paper. 



" Davis, J. J., New or Httle known species of Aphididae, Can. Ent. 4^: 226- 

 231, 1914. Symydobius alhisiphus new species. 



