122 Proceedings of the Royal Physical Society. 
description, or whether indeed this does not relate to the common 7. lineatum 
Clerck, quite another species. I am now introducing 7’. bellicoswm Sim. as 
new to Britain, and proposing to call that southern form, which we have 
hitherto called 7. lepidwm Walck., by the name of 7. instabile Camb. 
These two species resemble each other in many particulars, and these 
I shall not describe. I shall endeavour, however, to point out the numerous 
differences between them. 
T. bellicosum and TZ. instabile differ in the following respects:—1, size; 
2, colour; 3, proportions; 4, sexual organs; 5, male falces. 
Theridion instabile Camb. 
[Plate II. Figs. 8, 10, 12 and 13.] 
Theridion instabile Camb. Trans, Linn. Soc., xxvii, p. 416, pl. 55, No. 14. 
Size.—Total length of male, 2.2 mm.; of female, 2°2 mm. to 2°7 mm. The 
latter female was much distended with ova. 
Colour.—Similar in both sexes. Carapace.—Clear yellow-brown with a 
broad distinct dark brown central marking. This extends from the posterior 
end of the cephalothorax to the ocular area, which it generally passes, in 
these cases tingeing the clypeus. It is parallel sided, or slightly expanded 
at the ocular area. The sternwm is clear yellow-brown. These colours are 
practically invariable in all my specimens. Abdomen.—Very variable. The 
commonest arrangement for the upper side is its occupation by a large oval 
dark brown patch. This may be immaculate, or it may bear a central 
dentated band which, in all my specimens, is very narrow. The dark patch 
may be absent, and the central band may appear on a yellow-brown back- 
ground; or the abdomen may be of a pale yellow-brown colour, bearing 
a few pairs of dark blotches arranged longitudinally. Irregular white spots 
may ornament the whole or any part of the abdomen. Below, the abdomen 
is yellow-brown, the epigastric area not usually darker than the rest. 
Between this and the spinners a dark marking is nearly always present. 
In the male this takes the form of a transverse oblong, and in the female 
usually of an isosceles triangle with the apex pointing backwards. Occasion- 
ally, however, in the female the shape is oblong, or irregular, and sometimes 
even the whole mark is absent. 
Proportions.—The differences here are perhaps not very important. The 
average height of clypeus in the male is ‘22 mm. ‘The shape of the carapace 
of the male, as seen in profile, is rather characteristic. There is a gradual 
rise from the peduncle to the thoracic juncture, then a marked dip at the 
occiput, and finally a sudden rise at the caput. 
