SANBORN : KANSAS APHIDIDvE. 7 



The second type or incrassate form is used to describe when 

 the tube is distinctly enlarged or diminished in size or breadth. 

 This irregularity may occur any place on the tube, but when 

 at the distal end it is called clavate, and when in form of a grad- 

 ual distension, as shown in figure 12, it may be called vasiform. 

 The last or tuberculate type may partake of the first two forms, 

 but is never longer than broad. For illustrations of these types, 

 see plate II. 



The second type of appendage under consideration is the style. 

 It is an outgrowth of the last segment of the body. Of this 

 there are about three predominant types. (See plate 11.) The 

 first may be defined as ensiform. This is predominant among 

 the Nectarophorini. The caudal end usually tapers to a point, 

 and is generally turned dorsad, causing the dorsal boundary 

 line to become somewhat semicircular. The central part of the 

 style may be its broadest division. The second or cone-shaped 

 type is broadest at the base, from which it tapers to a point at 

 the distal end. This form is common to the Aphis. The third 

 type is known as globular. It may be constricted near the 

 center, so that a knob is formed at the distal end. The knobbed 

 is the larger form of this type. The other or subobsolete is 

 similar in size and shape to the former, with the constriction 

 and knob removed. The obsolete type of style is when the last 

 segment is not lengthened by any projection. Such a form 

 would be that shown in figure 26, plate IV. 



The Thorax. 



The second large division of the body is the thorax, which is 

 similar to that of other insects. Consequently only the wings 

 will be noted here as of special importance. It is from the 

 venation of these that the subfamilies are mainly distinguished. 

 When on foot most species carry their wings in a defiexed po- 

 sition ; i. e., the cephalic border or margin becomes the ventral 

 margin and lies near the lateral margin of the body, and what 

 is normally the caudal margin becomes the dorsal margin and 

 approximates dorsad the abdomen. The cephalic pair of wings 

 are much larger than the caudal pair, and in their color, vena- 

 tion and expansion depend specific characteristics. For illus- 

 tration of terms used, see plates. 



In the following descriptions of species the location and termi- 



