90 KANSAS UNIVERSITY SCIENCE BULLETIN. 



hirsute, but the distal one is furnished with heavy spines or 

 sensorial hairs. The end of the beak is rounded and heavily 

 chitinized, probably thus protected, as this portion rests upon 

 the food-plant during feeding. 



Set^. The setse are four in number, one pair assigned to 

 the mandibular processes and the other pair to the maxillary. 



The inner pair of maxillary setse are separated with diffi- 

 culty, as they appear to be tightly grooved, forming a tube. 

 The distal end of this pair extends beyond the other pair and 

 projects out of the distal end of the beak. (Fig. 38b, pi. XII.) 

 The distal ends of the maxillary setse are smooth and hair-like, 

 but curved slightly at the extreme tip. They lie between the 

 other pair until the first segment of the head is reached, when 

 they become caudad in position and separate from each other 

 on either side of the pharynx, disappearing into the head 

 cavity. The inner end of each seta is thickened and is joined 

 to the inner surface of the top of the head by heavy muscles. 

 From this muscle descends a muscle to the inner face of the 

 maxillary sclerite. (Fig. 41, pi. XII.) 



Mandibular Setse. — These are heavier than the maxillary 

 setae, although not as long. The distal end is blunt and its outer 

 edge or surface bears eight black teeth. (Fig. 37b, pi. XII.) 

 The setse lie laterad of and surround the maxillary setse in 

 their passage into the head, but on entering the head they lie 

 cephalad. These mandibular setse are thickened in the head 

 and connected to the sclerites by a well articulating joint. 

 (Figure 41 at v, pi. XII.) From this joint extends a heavy 

 muscle, which branches into two as it nears the top of the 

 head. 



For further investigation, observations must be based on 

 sections, both transverse and longitudinal. In making obser- 

 vations on sections to ascertain the structures of mouth parts, 

 it seems to be advisable to begin at the distal end of the beak 

 and carry our observations into the head, piece by piece. 



The general shape of the beak or labium is transversely 

 elliptical, the outline varying somewhat in the different seg- 

 ments. The back or dorsal side of the labium (the side which 

 lies against the sternum) is protected and strengthened by a 

 chitinized rod. (Fig. 40, pi. XII.) The labial wall on the ven- 

 tral side comes almost together, and then curves inward, form- 

 ing a groove in which the setse lie. 



