ESSIG, APHIDIDAE OF SOUTHERN CALIFORNIA 51 



of damage, first because of its rapid increase in numbers, and secondly because 

 it is able to do a life's work before the parasite finally gets the upper hand. In 

 this way much of the new growth is completely destroyed and the tree thereby 

 injured. By summer only isolated specimens of the aphid can usually be found. 

 I have referred this common Californian form to the Aphis citrl of Ashmead, 

 but it is only a provisional reference, since there appears to be no way in which to 

 tell what Aphis citri really is, except by a re-examination and description of 

 authentic material. 



C^allipterii^ jiislandicolii Koch 



Ptcrocallis ju'^laiidicola — Kalt. 

 Lachniis jiiglandicola — Kalt. 

 Aphis jiiglandicola — JValk. 



Winged Vivip.\rous Fe.m.ale. — (Figure 35). Length 2 mm., width 0.5 mm., 

 wing-expansion 3.25 mm. Prevailing color light yellow, many individuals hav- 

 ing two rows of black blotches on the back extending from the pro-thorax to the 

 Cauda. Eyes are red. 



Head short and as wide as the pro-thorax, with few short hairs on the frontal 

 margin between the antennae. Compound eyes large, bright red, with long terete 

 tubercles just behind near the posterior border. Antennae (Figure 36 E) arise 

 from head without tubercles, are shorter than the body, being 1.975 mm. long. 

 The tips of articles III, IV, V and VI are very deeply clouded. There are very 

 few hairs. Article VI has an apical nail-like process. The lengths of the respect- 

 ive articles are as follows: I 0.1 mm., II 0.1 mm.. Ill 0.375 mm., IV 0.225 mm., 



V 0.125 mm., VI 0.15 mm. The distribution of the sensoria is: I and II none, 

 III one row of seven large circular, IV none, V one large circular near distal end, 



VI several small ones in the nail-like process. Pro-thorax without lateral tuber- 

 cles. Rostrum short, not reaching the coxal cavities. Abdomen distinctly seg- 

 mented, in many cases having two rows of black blotches on the back. With few 

 hairs and no digitules. Cornicles short, with trumpet-shaped openings. Legs 

 moderate in length, more or less hairy, without sensoria. Hind tibia with a large 

 black blotch on the distal end. Wings hyaline, veins slightly pigmented at the 

 base. Primary wings, length 2.45 mm., width 0.75 mm. Cubitus well defined 

 Stigma long and narrow. Radius well curved. First and second obliques 

 straight, third well curved and twice-forked. Secondary wings, length 1.45 mm., 

 width 0.5 mm. Two discoidals. Sub-costal bends down at the base of the sec- 

 ondary discoidal and extends to the wing-tip. 



First discoidal is straight and arises from the sub-costal nearly one-half its 

 length and extends nearly to the margin. Second discoidal curves slightly in and 

 arises from the sub-costa at about two-thirds its length and extends nearly to the 

 margin. Cauda rounded and hairy. Style obscure. 



Apterous Viviparous Female. — This form has not been obtained, although 

 close watch has been kept since the first of January. 



Pupa of Viviparous Female. — (Figure 36 A, B. C.) In shape and color 

 the pupa resembles the adult form. On the frontal margin the hairs are replaced 



