J 2; OHIO STATK ACADEMY OP 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 pectus. 



The rnetathorax 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, 

 libia and tarsus. Each tarsus contains five segments of which 

 the last or fifth bears a pair of clazvs, a pair of pads or pulvilli 

 beneath the claws, and between the pulvilli a single empodium, 

 which is developed similar to the pulvilli. The prothoracic coxae 

 are slightly more than half as long as the femora of these legs, 

 while the coxae 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 apkal 

 yellow knobs are always visible. , ■: 



Wing.. Plate II show's the regions, and venation of a wing 

 of Tabanus stygius Say, and- reference to the drawing will make, 

 it easy to locate them. 



