22 BULLETIN 826, U. S. DEPARTMENT OF AGRICULTURE. 



The wing veins are not reduced in most species. In some, however 

 the radial sector of the fore wings is very faint or entirely absent. 

 This condition is met with in several genera of the Callipterina. That 

 it is this vein which is lacking is indicated by the trachea of the freshly 

 emerged wing. Here the media is represented by M x , M 2 , and M 3+4 . 

 The cubitus and first anal are distinct tracheas, whereas the second 

 anal is faintly indicated. In the hindwing besides the radial sector 

 three oblique tracheae are present ; these are the media, cubitus, and 

 first anal. Only the media and cubitus are represented in the vena- 

 tion. 



Considerable variation is met with in the cornicles of this tribe 

 but they are never long and prominent as in the Aphidini. The usual 

 form is the truncate one represented in Myzocallis, Chaitophorus, etc. 

 Very often the cornicles are sculptured. In some cases they 

 are reduced to small cup-shaped structures and in others they are 

 represented by mere rings. 



The antennae, as a rule, are long and slender and armed with few 

 sensoria. These sensoria are usually small, subcircular or oval. In 

 rare cases they are somewhat elongate. 



The oauda in this tribe is as a rule knobbed and the anal plate 

 bilobed. In some cases, however, the cauda and anal plate are both 

 rounded. In the Saltusaphidina the anal plate is divided and the 

 cauda remains distinctly knobbed. 



Wax secretion is present to a limited extent in this tribe. It is 

 most developed in the Phyllaphidina. Here there are large lateral ab- 

 dominal wax plates in all of the forms and the insects present a wool- 

 like appearance on the foliage. In the genus Euceraphis wax secretion 

 is found to a limited extent. In one species, mucidus Fitch, it is, 

 however, abundant and the insects of this species often seem to 

 float in the air, a peculiar appearance common also in the Erioso- 

 matinae. In the Saltusaphidina also distinct wax plates occur, 

 particularly in the oviparous forms. These are arranged along the 

 abdominal segments. 



The habit of leaping is common in the Saltusaphidina as the name 

 implies. Here the muscles of the femora are greatly enlarged for this 

 purpose. Many of the other members of the tribe approach this con- 

 dition, especially in the genus Monellia. Others, although they do not 

 distinctly leap, drop so suddenly when disturbed that they almost ap- 

 pear to leap from the foliage. Our common Symydobius on the 

 birch is difficult to collect on account of such a habit and other forms 

 of Callipterina are very similar in action. Certain species in this 

 tribe are closely attended by ants in return for the honeydew excreted. 

 Some species are protected by these Hymenoptera by means of sheds 

 or roofs built over colonies on the leaves or twigs. These sheds are 

 found quite commonly upon the leaves of the oaks protecting the spe- 



