Group Aphidina, Family Aphididae 69 



lengths. With the increase of the antennae we also find a correspond- 

 ing increase of the antennal or frontal tubercles. Van der Goot has 

 shown that they have little value in distinguishing genera and are pres- 

 ent in the Aphidini as well as in the Macrosiphini ; they are also found 

 in the Calaphidini. 



The Aphidini may be divided into two subtribes, the Aphidii and 

 Hyalopterii. 



KEY TO TIII<] SUBTIUL5ES OF THE Al'HIDINI 



1. Cornifles usually much longer than broad, cylindrical, sometimes wider at base 

 and tapering, or distinctly swollen. A direct I'terocommini line. 



APHIDII 



2. Cornicles short, usually not longer than broad, when longer than broad they 

 are usually slender and narrowed ,it base. Indicating Chaitopnorini characters 

 in addition to the usual Aphidini. . . . HYALOPTERII 



A division or grouping of the genera of the Aphidini was sug- 

 gested by Baker (1920), and historically was expressed by Koch in 

 separating the genera Rhopalosiphum and Hyalopterus from the old 

 genus Aphis. Two of these are undoubtedly distinct lines or sub- 

 lines and so express a subtribal division, but this can not be said of 

 the third, tho it appears so. The Aphidii with cylindrical cornicles and 

 progressive increase of length within the division indicate a distinct 

 line from the Hyalopterii with their short cornicles, non-progressive 

 increase of length in which they agree better with the more primitive 

 Chaitophorini. Some of the .\phidii may have cornicles very short or 

 even wanting, but this can be shown to be a reduction ( retrogression ) 

 from the original longer type of the division. The enlarged or swollen 

 character of the cornicles in Rhopalosiphum and related genera would 

 at first appear to have similar value, which is not the case. Swollen 

 cornicles are not confined to the Aphidini, this condition is common 

 also in the Pterocommini and can be found in the Calaphidini ; it is 

 found in the Macrosiphini and is almost characteristic of the Myzini 

 as a tribe. Koch's genus Rhopalosiphum has given more trouble and 

 led to more misplacement of species than all the other genera put 

 together. Swollen cornicles is apparently a character that early cropped 

 out in the primitive stock from which the group Aphidina is derived, 

 and the same character has again repeatedly cropped out in the vari- 

 ous tribes of the group. It is an excellent generic character when the 

 various types of swellings are considered. At most the group can be 

 considered as a section in the Aphidii. 



It will be noticed from the bibliography of the tribe that Baker 

 (1920) considers it as a subtribe under the term Aphidina. Whether 

 it is considered as a tribe or subtribe is of minor importance, but 



