4 KANSAS UNIVERSITY SCIBNOK BULLETIN. 



In conclusion, the author thanks Prof. S. J. Hunter, the head 

 of this department, under whose advice and guidance this work 

 has been done. Expressions of appreciation are also due Miss 

 Marguerite Wise and Miss Miriam Palmer, of this department, 

 for assistance in the preparation of illustrations. Following 

 their names are the figures drawn by each. Other figures con- 

 tained were drawn by the author. 



Miss Wise : 1 to 27, inclusive, 30, 34, 35, 36, 39, 48, 49, 50, 

 53, 62, 64, 66, 67, 68, 69, 70, 71, 72, 74, 75, 76, 83, 84, 85, 89, 

 93, 94, 95, 100. 



Miss Palmer: 28, 37, 45, 56, 57, 59, 60, 61, 77, 78, 81, 86, 

 87, 88, 91, 96, 97, 98, 99, 101. 



IXTKODUCTION. 



Plant-lice or aphids belong to the family Aphididne and to 

 the suborder Homoptera in the order Hemiptera. They are 

 characterized as small, soft-bodied insects which receive their 

 nourishment in the form of liquid taken into their bodies by 

 means of setse which lie in a jointed beak. The distal end of 

 the latter is placed closely to the cellular tissue of the plant and 

 used as a guide by means of which the four small, bristle-like 

 setae are extruded into the live tissues of the plant, from which 

 the juicy nourishment is conveyed to the assimilative organs of 

 the insect. They have six legs, and they may have a pair of 

 compound eyes, three ocelli, two pairs of wings, a pair of 

 honey-tubes, a beak, and a style, but these parts are not con- 

 stant throughout the family. 



Tlie Heart. 



The first main division of the insect's body bears some very 

 important organs of classification. It always bears a pair of 

 antennae, one on each side of the dorsocephalic angle of the 

 head. Caudad of these are usually two large compound eyes, 

 which at their caudal margins have a few facets extending be- 

 yond the rest. These are called occular tubercles. Between 

 the eyes and antenn^r and a little mesad are two simple eyes or 

 ocelli ; also between the antenna'! and a little ventrad on the 

 front is another ocellus. On the ventral surface of the head 

 the beak or labium is attached. This is mainly characteristic 



