ATTACHMENT OF THE ABDOMEN TO THE THORAX IN DipTERA 265 
tergite (plt), are used. These are the terms which Crampton appropriates 
from Martin. In case there are two lateral plates formed, the writer has 
prefixed ana and kata to the term pleurotergite for the upper and lower sub- 
divisions, respectively, calling the upper one anapleurotergite (aplt) and 
the lower one katapleurotergite (kplt). 
The anterior phragma (Plate XXXII, 76, phg?,), or internal fold of the 
terga between the pro- and the mesothorax, is usually poorly developed in 
this group, and for this reason it 1s not indicated in the drawings. When 
present it usually projects under the pronotum. The posterior phragma 
(Plate XXXII, 76, phg’,) is well developed in the Brachycera (Plates XV, 
21, and XVI, 24). Very frequently the two lamellae, the one of the 
mesonotum and the other of the metanotum, are easily distinguishable in 
the composition of this phragma. 
The pleuron 
Primarily the pleuron plate is composed of two sclerites, the episternum 
(es?) and the epimeron (em?). The suture (pleural) formed by a more or 
less transverse infolding of the walls of this plate (Plates IX, 1, and XI, 
8, ap?) divides it into an anterior part, the episternum, and a posterior 
region, the epimeron. ‘This suture in its primitive condition extends from 
the wing process to the coxa, but in some of the higher Diptera, as Mus- 
cina stabulans (Plate X XII, 41), it may disappear altogether just above the 
leg. The primitive straightness of this suture as shown in Panorpa venosa 
(Plate XXXII, 76), in the Tipulidae (Plate IX, 3), in the Rhyphidae 
(Plate X, 4), in the Culicidae (Plate XII, 10), and in other forms, 
gives way in the more specialized members of the group to a prominent 
forward bending, in some cases, about midway dorsad from its origin 
at the coxa (Plates XX, 35, and XXII, 42). 
Secondary sutures may divide either the episternum or the epimeron, 
or both, into a dorsal and a ventral region, and in some cases the dorsal 
episternal area into an anterior and a posterior part. If common usage 
did not dictate differently, the writer would prefer to use the more descrip- 
tive prefixes ana and kata combined with the names of the primary sclerites 
in referring to these secondary divisions, and simply refer to the secondary 
division of the dorsal episternum as the anterior anepisternum. But 
because of their widespread acceptance by systematists of this group, 
the use of Osten-Sacken’s (1884) terms pteropleura and _ sternopleura — 
