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 foimd 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 x^th 

 of an inch in length. The general hvie 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 pro thorax 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 setae, knobbed at their extremities Hke the glandular haii-s 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 antennse, and the tarsi, were blackish. 

 The antennaj 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 fij-st, minutely annulated. 

 The basal joint was the thickest of aU, the second less thick, but stronger than the others. 

 The proximal half of the antennae was sparsely setose. The promuscis was short, extend- 

 ing, when deflexed, no further than the posterior edge of the prothoracic sternum. The 

 abdomen tapered into a cone beyond its sixth somite, on whose dorso-lateral region the 

 very short trvmipet-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 fu st 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 prolonged, so as to form a sort of inferior lip to the 

 vaginal aperture (PI. XL. fig. 1). The vagina (C) is a thick- walled tube provided with a 



• I do not think that my AphU of the Oak is identical either with that described by Reaumur, or that described 

 by Bonnet. None of my specimens attained the size of theirs, nor do cither of those writers mention the peculiar 

 dorsal markings of my species: furthermore, the proboscis in both Reaumur's and Bonnet's was long; in mine it is 

 very short. The proper specific names of both the Aphides alluded to iu this memoir will be discussed in a final note. 



VOL. XXII. 2 E 



