6 KANSAS UNIVERSITY SCIENCE BULLETIN. 



In connection with the labium may be mentioned the labrum 

 (plate I, figs. 1 and 4), which is also prolonged distally into a 

 sharp point. Its lateral edges are turned under so that they 

 approximate on a median ventral line, which is chitinized. At 

 the proximal end the folds diverge. This forms a sort of guide 

 directly ventrad the antelabial sclerite, while the distal end 

 of the labial sclerite extends a little beyond or caudad of this. 

 The need of these two sclerites may be clearly understood when 

 the motion of the labium is considered. For instance, suppose 

 the insect to be in a feeding position. The setae then are all 

 straight, but when the insect removes the labium to its venter 

 again, after feeding, it will then be at right angles to its former 

 position, and the wire-like setcC will have been drawn nearly at 

 a right angle over the antelabial sclerite. Again, when the 

 labium is brought into a feeding position, the canal being short- 

 ened, will cause the setie to be bent outward, but the labial 

 sclerite helps to hold them in the canal, the latter being almost 

 eliminated at this point on account of the bend. Therefore, on 

 account of the motion of the labium and of the absence of the 

 canal at this point, this need of special devices for holding the 

 set?e may be seen. 



The Abdomen. 



The third division of the body is the abdomen. Its shape 

 depends largely upon its distension. Since the latter varies 

 with age or on account of food material, it is hardly necessary 

 to formulate any characteristic basis upon its size. Its color 

 and appendages, however, are of importance. And, in addition, 

 there is present in some forms an external covering of pulveru- 

 lent or cottony material. By the appendages are meant the 

 honey-tubes* and the style. And although tubercles may be 

 present, they are not considered as the former. 



The honey-tubes are external openings on the dorsal side of 

 the sixth segment. These are of various sizes and shapes. 

 The four principal types may be defined as cylindrical, incras- 

 sate, clavate, and tuberculate. The first type is the most com- 

 mon, but it is seldom perfect. For instance, a honey-tube of 

 two millimeters in length may be a shade narrower or broader 

 in some part of its length and yet be defined as cylindrical. 



4. Tlie exact function of these organs has never been scientifically determined, but it has 

 been lately conceded that they are purely excretional, and not " secretional." Other names 

 used to denote these are horns, cornicles, nectaries, and siphuncles. 



