268 BrengaMiIn P. Youne 
Examples of such a development are found in Plates IX, 2, X, 4, 5, and 
6, XI, 7, XII, 12, XIII, 13, 14, and 15, XIV, 18; X{Vilie 27 amd exanxe 322 
On the other hand, there are examples of the opposite development, the 
epimeron becoming greatly enlarged at the expense of the episternum, 
as in Dolichopus cuprinus (Plate XVIII, 29). 
Another common peculiarity in the epimeral region is the failure of the 
hypodermal cells of the ventral part of this area to lay down chitin in 
the integument, with the resulting appearance of the epimeron’s moving 
dorsad (Plates X, 6, XI, 7, XIII, 14, XIV, 16, 17, and WS) Sexes 2 xexe 
34 and 35, X XVI, 57, X XVII, 62, X XIX, 67). Many examples of very 
weak chitin in this lower epimeral sclerite are to be seen. In fact, it is 
often difficult to say where the epimeron leaves off and the interseg-. 
mental abdominal membrane begins (Plates XIII, 13, X XI, 38 and 39, 
XXII, 41, XXX, 70 and 71, XXXI, 72). 
An interesting variation in the lower Nemocera, and one that is 
very difficult of interpretation, is the movement cephalad of the episternum 
(es?) into the mesothorax, with a resulting crowding of the compound 
sclerite mep? into a very small area above the mesothoracic coxa (Plates 
X, 5 and 6, XI, 9, XII, 10 and 11). 
The movement forward of both pairs of legs has caused a decided pro- 
longation of both the episternum (es*) and the epimeron (em?) in Lep- 
togaster loewi (Plate XVIII, 28) and in Gastrophilus intestinalis (Plate X XI, 
37); while the prolongation of the coxae in Leia winthemi (Plate XII, 12) 
apparently results in the movement of the episternum (es*) and the epi- 
meron (em*) down on the base of the legs. 
Sutures sometimes become vestigial, as in the case of Oncodes incultus — 
(Plate XVI, 23) in which the pleural suture shows no implex nor scarcely 
any external evidence of having once existed just above the base of the 
coxa. The suture between the lower epimeron of the mesothorax and 
the metathoracic episternum is lacking in Dixa modesta (Plate X, 5) 
and in Phora concinna (Plate XIX, 32). 
What seemed to be sense pits were found on a number of species, on 
either the tergum or the pleuron of the metathorax or the basic segments 
of the abdomen. In a number of cases these have been figured, as in 
Thereva fucata (Plate XVII, 25, em*® and 2s), in Leptogaster loewt 
(Plate XVIII, 28, t*), in Chrysopila ornata (Plate XV, 21, 2t), and in 
Hirmoneura sp. (Plate XVI, 22, 2t and Qs). 
