12 OHIO STATE ACADEMY OF SCIENCE. 
as dorsun and pleura; at the sides of the middle of the dorsum is 
‘a suture, furcate below and obsolete above, the transverse suture. 
In Diptera it seems not to be definitely settled as regards the 
downward extension of the pleura, but “the inferior surface of 
the thorax between the legs” has received the name of pectuts. 
The metathorax is small and the metanotum, which is the 
part of it visible from above, may be seen beneath the scutellum, 
by viewing from behind. 
Passing toward the pectus on each side we observe a promi- 
nence called the lateral callosity of the metathorax. Behind the 
lateral callosities are located the poisers or halteres, and just be- 
neath them the posterior thoracic spiracles. 
The prothorax bears a pair of legs, the mesothorax a pair of 
legs and the pair of wings, and the metathorax a pair of legs 
and a pair of halteres. 
The legs are each composed of five sections; the coxa next 
the thorax, and following in succession the trochanter, femur, 
tibia and tarsus. Each tarsus contains five segments of which 
the last or fifth bears a pair of claws, a pair of pads or pulvillt 
beneath the claws, and between the pulvilli a single empodium, 
which is developed similar to the pulvilli. The prothoracic coxz 
are slightly more than half as long as the femora of these legs, 
while the coxz of the other legs are very much shorter. 
There seems to be no notable difference between the legs of 
male and female except in the front feet where the male claws, 
pulvilli and empodii are much larger than the same parts in the 
female. 
By taking a specimen of Tabanus with its wings spread and 
following the posterior border of a wing toward ‘the body one 
finds toward the base an incision, the axillary incision, between 
which and the scutellum are three membranous lobes. These in 
order are called alula, antitegula and tegula. 
The first, bordering the axilliary incision, is considered as 
a part of the wing proper, but the other two called tegulae when 
taken together are usually considered as accessory. In closing 
the wing it is seen that the antitegula moves with the wing while 
the tegula, although joined with the antitegula is also securely 
joined with the thorax, remains practically stationary. When 
the wing is closed the antitegula fits over the tegula and nearly 
hides it from view. The halteres have their attachment beneath 
the tegula, therefore their basal parts are concealed, but the apical 
yellow knobs are always visible. 
Wing. Plate II shows the regions and venation of a’ wing 
of Tabanus stygius Say, and reference to the drawing will make 
it easy to locate them. 
