18 BULLETIN 100, U. S. DEPARTMENT OP AGRICULTURE. 



earliest egg deposition may be explained by the fact that until late 

 in August males are quite scarce and so the females must wait on 

 the leaves until the males are developed. Directly after mating the 

 female repairs to the branches and limbs to deposit her eggs. Al- 

 though eggs may be deposited anywhere along the limbs, and more 

 rarely on the newer growth, the locations most preferred are the old 

 scars of fallen leaves and the surface of the larger limbs near their 

 bases. Another favored location is that in the crotches of the smaller 

 limbs. Eggs are rarely laid along the stalk of the leaf or at the base 

 of the leaflets, and if placed in those positions they fall to the ground 

 when the leaf drops. Cavities and interstices in the bark are also 

 chosen, but when infestation is very severe the eggs are laid in the 

 open on the larger linibs (see PL II) . In such a case large groups of 

 eggs are massed together by many females, but a single female lays not 

 more than three or four in a group. The eggs are fastened together 

 and to the plant surface by a thin, transparent, gluey substance. No 

 accurate information was obtained as to the number of eggs a single 

 aphis produced, but from general field observations together with 

 dissections of gravid females the writer arrived at the conclusion that 

 not more than 30 eggs fell to the share of each adult, and probably 

 not over half that number. On July 20, 1911, five gravid females 

 were dissected. These contained respectively 5, 3, 3, 4, and 4 well- 

 developed ova, besides about a dozen much smaller ones. On August 

 28, 1912, four oviparous females dissected contained respectively 

 2, 2, 4, and 2 full-grown ova besides about 20 much smaller ones. All 

 these individuals were taken on the leaves and had not oviposited. 

 The largest eggs dissected were lozenge-shaped and measured 0.37 

 mm. in length by 0.14 mm. in width. 



THE EGG (FIG. 1; PL. II). 



When first laid, the egg is pale lemon-yellow or whitish yellow, oval, 

 almost twice as long as broad, flatter than most eggs of Aphidida?, 

 and slightly broader at the micropylar end. After two or three days 

 it turns black and shines obscurely when placed under a strong light. 

 The surface is beautifully sculptured with granular hexagonal mark- 

 ings. These markings are thickened portions of the shell. The nar- 

 row intermediate portions of the shell are extremely thin, so much so 

 that four months after the egg has been laid the yellow interior sub- 

 stance is plainly visible through them if subjected to a high power of 

 magnification. It appears that about 85 per cent of the eggs are 

 fertile. The average size is 0.50 mm. by 0.28 mm. The egg stage 

 may be said to occupy, on the average, five months in California. 



