A. J. Grove 
3 
air from the tracheae before the jelly has solidified sufficiently to stop 
up the stigmata. 
Whenever possible, the drawings were made with the camera 
lucida, and in the diagrammatic ones the proportions were obtained 
from camera lucida sketches. 
External characters. 
Buckton (1875—1882), in his Monograph, gives the distinguishing 
features of S. rosarum as follows : 
Long, oval, flat. Wholly green, ringed, the posterior edges fringed 
with capitate hairs which mostly spring from small tubercles. Vertex 
tufted. Antennae and legs somewhat short. Frontal tubercles small. 
Eyes reddish brown. Tail green, and not conspicuous. 
This description certainly includes most of the distinguishing 
features of S. rosarum ; and it is only intended here to give in more 
detail points not brought out in the above description. 
The body consists of head, thorax and abdomen; the first two 
together forming the anterior half of the body and the abdomen the 
posterior half (Text Figs. 1 and 2). 
The segmentation of the body is not so markedly clear as Buckton 
seems to infer. The three segments of the thorax are fairly distinct, 
and, on the ventral surface only, the segments of the abdomen can be 
made out, but they are almost invisible on the dorsal surface. 
When the Aphis is viewed from above, the most striking feature is 
the rows of capitate hairs (cap. h.) which Buckton mentions. These are 
arranged in six rows—three on each side of the median line (Text 
Fig. 1). The two middle rows are more prominent than the others 
from the fact that the tubercles or excrescences upon which the hairs 
are mounted, are more pronounced than in the other cases. Moreover, 
in these median rows each tubercle bears two hairs and the rows are 
continued right to the front of the head. In the other cases the rows 
are confined mainly to the abdomen. These hairs are also found for a 
short distance on the legs, usually ceasing at the beginning of the tibia, 
so that towards the end of that joint the hairs are of the usual tapering 
kind. A remarkable feature about the feet of the Aphis is the 
reduction of the number of the tarsi to one (Text Fig. 4). This is 
described by Buckton. The antenna (Text Fig. 5) of S. rosarum —in 
common with all the genus Siphonophora —consists of six joints. The 
last joint is very peculiar, it being composed of two parts—an expanded 
1—2 
