n YMEN OP TER A. 
603 
The Parapstdes .—in this order the scutum ot the mesothorax is 
divided into three parts by two longitudinal sutures; the lateral por- 
Fig. 732. A Chalcis-fly: 1. pronotum; 2, 2, parapsides; 3, mesal part of the scutum 
the mesothorax ; 4, scutellum; 5, tegulae. 
of 
tions of the scutum thus separated from the mesal part (Fig. 732, 2,2) 
are termed the parapsides (pa-rap'si-des). 
The Wing-veins .— It is much more difficult to determine the 
homologies of the wing-veins of the Hymenoptera than those of 
either the Lepidoptera or the Diptera; for in this order the primitive 
plan is much more obscured. The best way to learn the wing-veins 
of the Hymenoptera is to make first a careful study of those of the 
Diptera, and then to compare the front wing of a generalized 
hymenopterous insect with a wing of one of the more generalized 
Diptera; for this purpose take the front wing of a saw-fly of the 
genus P amp hi Hus (Fig. 733) and that of Tabanus (Fig. 539, p. 454). 
In Pamphilius (Pam-phil i-us), and in most other Hymenoptera 
also, the anal furrow or vein VIII is easily recognized as a concave 
fold, in the position indicated by the doited line (Fig. 733, VIII). 
Having found this, a very important landmark is established. 
Next it should be understood that the Hymenoptera belong to 
that series of orders in which veins IV and VI are not developed; 
therefore the veins that lie in front of the anal furrow are veins I, II, 
III, V, and VII. 
Vein I forms the costal border of the wing, as in the Diptera 
(Fig. 733 . I). 
Vein II is usually absent in the Hymenoptera; but in Pamphilius , 
and in a few other genera, it is well preserved (Fig. 733, II). It is 
simple, and is usually connected with vein III by a cross-vein. 
Vein III is the most difficult of all of the veins to understand. A 
very careful study of the problem has convinced the writer that this 
vein is typically five-branched in this order, resembling in this re- 
