AND MORPHOLOGY OF APHIS. « 203 
made their appearance. Therefore, being extremely desirous to compare the process of 
the development of the germ'with that of the ovum, before completing this paper, I began 
in the last days of October to seek for oviparous females of some other species, 
An Oak-tree in the Zoological Gardens at length supplied me with that which I sought. 
The small twigs and leaves afforded habitation to a number of minute wingless Aphides, 
all so nearly equal in size, that I did not doubt their non-viviparous, and hence in all 
probability their oviparous character. 
Microscopic examination fully confirmed my suspicions; for not only were the Aphides 
full of ova, but I found multitudes of similar ova adhering to the plant in the axils of the 
leaves, and more particularly between the outer bracts of the buds*. 
These Aphides were very different from my viviparous species. They were about th 
of an inch in length. The general hue of the body was pale green ; but it was diversified 
in the dorsal region by four longitudinal rows of blackish rounded spots, one spot in each 
row being seated on the tergum of most of the somites, from the prothorax backwards. 
Hence, there were nearly as many transverse rows of four spots each, as segments of the 
body. The two median spots in each row were larger, and situated close to the middle line. 
The external spots were more upon the sides of the body. The spots upon the mesothorax, 
and thence to the sixth abdominal somite inclusive, were the largest and most conspicuous. 
Each spot was constituted by a dark elevation of the integument, which supported a 
tuft of long setæ, knobbed at their extremities like the glandular hairs of certain plants. 
The hairs were not confined to these localities, however, but were scattered over the head 
and other parts of the body. The eyes were red, and produced into a small tubercle on 
their posterior margins. The distal portions of the antennæ, and the tarsi, were blackish. 
The antennæ were not more than equal to half the body in length ; they were seven-jointed, 
the penultimate joint being somewhat swollen at its extremity. Both this and the pre- 
ceding and following joints were so sculptured as to appear, at first, minutely annulated. 
The basal joint was the thickest of all, the second less thick, but stronger than the others. 
` The proximal half of the antennæ was sparsely setose. The promuscis was short, extend- 
ing, when deflexed, no further than the posterior edge of the prothoracie sternum. The 
abdomen tapered into a cone beyond its sixth somite, on whose dorso-lateral region the 
very short trumpet-mouthed siphons were situated. The abdomen was terminated by 
two subcylindrical rounded setose tubercles, of which the lower was the larger. They 
had the anus between them, and acted as anal valves. The posterior limbs, when fully 
extended, hardly reached beyond the end of the abdomen. 
The eggs when first laid are of a dark green hue and very soft; afterwards they ap- 
pear to become black. : 
The vulva of the oviparous Aphis (B) opens between the eighth and ninth abdominal 
sterna, the eighth (8) being a little prolouged, so as to form a sort of inferior lip to the 
vaginal aperture (Pl. XL. fig. 1). The vagina (C) is a thick-walled tube provided with a 
* I do not think that my Aphis of the Oak is identical either with that described by Réaumur, or that ee 
by Bonnet. None of my specimens attained the size of theirs, nor do either of those vem mention the peculiar 
dorsal markings: of my species: furthermore, the proboscis in both Réaumur's and — wem long ; dl. it 18 
very short, The proper specific names of both the Aphides alluded to in this memoir will be discussed in a note. 
YOD: XXII, dim 
