328 



JOHN B. SMITH. 



Fig. 7. Mouth parts of Tabanus lineola. 



along the meiituni. The palpi are not at all functional, but are 

 rigid, not articuhited, yet not entirely connate with the paraglosscB. 

 In Tabanus lineola (I feel safe in this detenuination) the palpi are 

 still more distinct, but not yet free, noi' have I found any species in 

 which they are functional. I have a very strong conviction, how- 

 ever, that somewhere in the Diptera some vicious beast will be found 

 in which the palpi are entirely free, and possibly functional. The 

 figure of Tabanus lineola is here inserted to show the relative position 



of the ])arts, as attached to 

 the head. No effort has been 

 made to difi'erentiate the galear 

 structure, which is highly spe- 

 cialized here. Returning to 

 the study of fig. 6, we find the 

 right hand figure to represent 

 the lacinia (mj), the palpifer 

 (st.) and maxillary palpi 

 (mxp), in their relative posi- 

 tions, attached together. The 

 lacinia alone {mx) is shown to 

 the left of the labium, and at the extreme left are the palpus (7nxp) 

 and palpifer (st). This figure shows the development of an impor- 

 tant tendency in the palpi. It will be noted that, at the base, there 

 is but a flat strip connecting with the base'of the palpifer, and that 

 the joint becomes a complete cylinder only near its tip. The chiti- 

 nous band forms the real base of the palpus, but the membranous 

 extension from the margin of the head envelopes the base of the 

 mouth, and the palpal joint first becomes complete on the outer side 

 of this membrane. That is to say, outside of the enveloping mem- 

 brane, the palpus is complete, but within the head the joint becomes 

 partly muscular, and the chitinous cylinder is incomplete. This is 

 important, for it is the beginning of the complete separation of the 

 palpi from the functional mouth parts. 



The next step will be noted in the Asilidte, of which Erax sp. and 

 Asilus sericeas will be figured. 



In Erax, we have at figure 8, c, the appearance of the mouth parts 

 from the front, showing the attachment of the palpi (the dotted por- 

 tions representing membrane) and the method in which the palpifer 

 enters the galear structures. The terminal joints of the galea are 

 completely separated, but the basal joints are united beneath. The 



