A. J. Grove 
9 
enter into that discussion, but rather to give as accurate an account as 
possible of the mouth organs of the species under consideration. 
S. rosarum, like other Aphides, possesses a chitinous framework in 
the head for the support and control of the mouth organs. Whether 
this corresponds to the tentorium usually present in the head of insects 
is rather doubtful ; at least it is much more complex than the usual 
type of tentorium. Fig. 1 (Plate I) gives a general frontal view of 
this chitinous framework, and it agrees in some points with the figures 
given by Witlaczil and Krassilstschik ; but, at the same time, there are 
points of difference, especially in connection with the lower parts. 
It will be necessary first to describe in detail this framework, and in 
doing so, reference will be made to similar arrangements in other 
Aphides. 
The chitinous framework. Traversing the head from side to side, 
in a position about two-thirds of the distance, dorso-ventrally, from the 
ventral side of the head, there is a strong, hollow, slightly curved rod of 
chitin, which is closely applied to the under surface of the cerebral 
ganglia (see Plate I, Fig. 4). From this rod the whole of the chitinous 
framework depends, and to it most of the muscles controlling the mouth 
parts are attached. Compared with the figures of Mark (1877), Kras¬ 
silstschik (1892 and 1893), etc., this rod corresponds with their “Arcus 
superior,” but I think the term “ Transverse bar ” is more appropriate. 
This bar has two pairs of chitinous supports, which may be termed the 
“Anterior and Posterior lateral rods,” one pair arising from its anterior 
face, and the other pair from its posterior face. These supports arise 
from the ends of the bar, and consist of slender hollow rods of chitin, 
joining the bar to various parts of the head. The anterior lateral rods 
pass almost horizontally forwards, closely applied to the under surface 
of the expanded portion of the cerebral ganglia, so that the tapering 
portions of the ganglia lie between them. This pair eventually becomes 
continuous with the chitin of the front of the head. The posterior 
lateral rods dip down at a considerable angle and finally become 
connected with the ridge which marks the junction of the head with 
the first thoracic segment. 
Depending from the centre of the tranverse bar or rod are two rod¬ 
like pieces of chitin which are arranged in the form of an inverted Y 
(A), the junction of the two arms corresponding with their point of 
attachment to the transverse bar. The arms of the A-shaped bar are 
divided towards the lower end by a kind of joint, and finally they both 
make a strong curve inwards and become continuous with the chitin of 
