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maxillae are more easily separable. Removing them from 

 the labium note the channel in which they naturally lie. 

 The labium is more strongly chitinized along the walls of 

 the channel than elsewhere, except at its tip. 



Make a drawing of the month-parts from dorsal view, 

 with mandibles and maxillae removed from channel of labium 

 and spread apart. 



THE MOUTH PARTS OF THE HORSE-FLY. 

 ( Tabanus sp.) 



Select a female horse-fly (distinguished from the males by 

 the narrow space between the eyes ; in the males the eyes 

 touch for a greater or lesser distance along the dorsjmeson 

 of the head). The projecting mouth-parts are conspicuous. 

 On superficial examination there may be noted two, thick- 

 ened, slightly-curving, horn- or club-like processes (the 

 maxilliary palpi) projecting above a black, thickened stalk 

 or trunk (the labium), lying on the dorsal surface of which 

 a number of light-brown, slender, pointed stylets may be 

 seen. 



For more detailed examination of the mouth-parts the 

 head of the fly should be removed from the body, a consid- 

 erable part of the head, laterad and caudad, broken away 

 and the remainder, with mouth-parts attached, boiled in 

 K O H to soften and bleach. 



The large maxillary palpi are two-segmented; the distal 

 segment is longer than the basal one, and compressed. The 

 proximal one is subcyliudrical, and projects dorso-cephalad, 

 so that the large distal segment is carried above the rest of 

 the mouth-parts. 



Lying along the dorsal surface of the large labial trunk 

 are six, long, slender, pointed pieces or stylets. The upper- 

 most, unpaired, flat piece is the labriun (or perhaps labrum 



