MEMBRA CIDJE. 
1 o 
O 
The mesonotum then appears to be composed of two shining chitinous lobes or 
bullae, which form the attachments internally of the bundles of muscles which move 
the alary organs. These oval convex protuberances may be seen in Umbonia spinosa 
and U. orozimbo. Also in Membraces tectigera and M. cdta.\ see PI. A, Figs. 6, 11, 12, 
These processes are quite independent of the pronotal sheath. Above them there 
is a smaller shining lobe, the significance of which is not so obvious, but it occurs in 
other insects. 
The crescentic process for articulating the pronotum may be seen in PI. A, 
Fig. 10, and in profile in Fig. 6. Also the situation of the septum above 
noted Fig. 13 d. 
The Scut'ellurn. —This portion of the thorax is very little developed in Membracidae, 
though in the allied Jassidae it is often very visible and obvious. 
In the Membracidae it can rarely be seen, though always present. This obscurity 
is due to the great development of the pronotum, which entirely covers it, except in 
the subdivision Centrotidae, in which case the pronotum is either raised above it by a 
clear space, or else the pronotum is very short, and but little developed. 
The scutellum in insects has by no means the same anatomical importance as the 
other great divisions of the thorax, for no special organs like wings or legs proceed 
from it. 
It thus proves a valuable help in the identification of species, for it seems to be a 
rule, that the less specialised a part of an insect is, the more constant it is in form, 
for it is not necessarily modified by the requirements of organs attached to it, and 
their adjuncts. 
When the pronotum is foliaceous in form, as in Membracis, and thus composed ot 
two distinct layers, the representatives of the mesonotum and the metanotum can be 
easily seen, and the same may be shown by the careful removal of the large thorn¬ 
like sheath ol the pronotum in Umbonia. In these cases, viewed from the back, the 
pronotal attachment occurs as an angular process near the head, and below this three 
considerable bullae, or shining, horn-like protuberances mark the attachment of the 
internal muscles which work the tegmina and wings. 
Under the last of these bullae the scutellum may be found lying above the first 
segment of the abdomen. In Umbonia spinosa this is figured in profile, Plate A, 
Fig. 6. In Membracis alta, Plate A, Fig. 10, it is seen from above. 
Though never large, the scutellum is uncovered in the Centrotidse. Perhaps it 
has its greatest development in the genera ./Ethalion and Tolania. 
Many Centrotidse are conspicuously marked with a white triangular patch near the 
middle of the pronotum, which may or may not represent the scutellum. The spot 
is covered with a shining felt or velvety, pile-like substance. This structure however 
