a 
120 Prof. Westwood’s Observations on the 
inerassated spot separated from the extremity of the 
subcostal vein by a very short clear space, which repre- 
sents the stigma of the ordinary hymenopterous wing. 
In S. vigilans the extremity of the subcostal vein 
appears to be continuous with the stigmal spot (Plate V., 
fig. 8a), and in S. JWollastonii (Plate V., fig. 2 a) , the 
median or discoidal vein simply forms a closed cell with 
the subcostal, and does not emit a spur or branch back- 
wards into the disk of the wing. 
The legs in this genus are comparatively slender and 
simple, not exhibiting any of the strong series of spines 
found in the fossorial Hymenoptera 
Some of the species of this genus ‘exhibit a remarkable 
instance of dimorphism and even trimorphism in the 
females, some of which are furnished with certain of the 
characteristics of the opposite sex. Sir 8. 8. Saunders, 
in addition to the ordinary female of S. ephippium, 
destitute of wings and of ocelli, found one agreeing in the 
general form of the body with the females, but possessing 
the fully-developed wings and ocelli of the male. - Re- 
membering the diversity in the size of the heads of 
different individuals among some of the species of ants, 
I was curious to ascertain how far this character was to 
be found in these different individuals. Their heads 
were therefore drawn of a large size by the camera 
lucida, which were then carefully reduced by measure- 
ment, when it appeared that the heads of the normal 
females were slightly longer than wide, whereas the head 
of the winged and ocellated female was considerably 
broader than long, although its length agreed very nearly 
with that of the normal female. Their relative pro- 
portions may be expressed by the following figures :— 
LONG. WIDE. 
Head of normal female without 
wings or ocelli_. : Pony 75 
Head of female with wings Eat ocelli 78 90 
-~] 
These measurements may be contrasted with those of 
the normal male and female of S. cylindrica from Prevesa, 
drawn to the same seale :— 
LONG, WIDE. 
That of the winged and ocellated 
male being i PioaGl 60 
That of the wingless ale Beane 
lated female being J : ist: OF 78 
