WALNUT APHIDES IN CALIFORNIA. 



39 



orange-colored; cylindrical, long oval, slightly tapering to either end, 

 four times as long as broad; deposited in compact masses of from 5 to 

 25 on the leaf, usually on the underside, and with their long axis at 

 right angles to the leaf surface; size, 1.3 by 0.35 mm. The larva: All 

 black at hatching, later with pale markings, becoming more distinct 

 after each successive molt. After the third molt the general color 

 is dark purplish-black, with a median line of pale brick-red spots on 

 the thorax and abdomen and also two lateral rows of similar spots. 

 On segments 1 and 4 of the abdomen occur also two pale spots, one on 

 either side of the median brick-colored spot and midway between it 

 and the corresponding lateral spot. The full-grown larva has a 

 length of 8 millimeters. The pupa: General color white, wing pads 

 sienna brown. A large number of black spots and dashes are present 

 but the prevailing color is white. Average size, 4 by 3.3 mm. The 

 adult: Hemispherical, ashy-gray, with black markings, the elytra 

 sometimes diffused with dull reddish blotches; head black, with 

 central portion white or light gray; thorax (pronotum) black, with 

 gray margins; elytra ashy-gray, with eight black spots on each 

 elytron; legs yellow; abdomen reddish-yellow; average size, 5.2 by 

 4.2 mm. The adults of this species, if confined without food, will 

 devour one another. 



Table XIII indicates the predatory activities of two larvae of 

 Adalia melanopleura on walnut plant lice. 



Table XIII. 



-Adalia melanopleura: Predatory activities on walnut plant lice, Walnut 

 Creek, Cal., 1912. 



Larva 

 No. 



Date of 

 hatching. 



Date of 

 molt 1. 



Num- 

 ber 



"lice" 



eaten 

 to 



molt 1. 



Date of 

 molt 2. 



Num- 

 ber 

 "lice" 

 eaten, 

 molts 

 lto2. 



Date of 

 molt 3. 



Num- 

 ber 

 "lice" 

 eaten, 

 molts 

 2 to 3. 



Date of 

 pupa- 

 tion. 



Total 

 "lice" 

 eaten. 



Date of 

 adult 

 emer- 

 gence. 



1 

 2 



Sept. 17 

 17 



Sept. 20 

 19 



41 

 35 



Sept. 24 

 22 



38 

 34 



Sept. 26 

 25 



30 

 33 



Sept. 30 

 30 



181 

 194 



Oct. 12 

 12 



In all, 375 plant lice were eaten in 26 days, or 14.4 per day per larva. 

 The feeding period of both larvae was 13 days as contrasted with an 

 average of practically 18 days for the larvae of the ashy-gray lady- 

 bird. Adalia melanopleura is considerably smaller than that species, 

 its larva consuming in a period of 13 days half as many plant lice 

 as the larva of the larger species will devour in 18 days. This 

 larger species will consume 70 larvae in a single day while the maggot 

 of the large syrphid fly (Catabomba pyrastri) will dispose of over 100 

 and during the 23 days or so of its existence will devour over 1,000, or 

 about 43.5 lice per day. However, in contrasting the two groups of 

 predaceous insects — Syrphidae and Coccinellidae — it must be remem- 

 bered that the former are aphidophagous only in the larval state 



