TRIBES OF APHIDIDAE 47 
corrected this to Aphidae, the term generally accepted by British 
authors. Burmeister (1835) used the term Aphidina, which has been 
extensively followed by authors on the continent. Other terms pro- 
posed but not generally accepted are: Aphidiae, Zetterstedt (1840) ; 
Gradipedes, Amyot et Serville (1843); Aphidinae, Rondani (1848). 
Harris (1852) used the form Aphididae as now accepted by the best 
writers. 
Morphological characters. Much importance has been given to 
the form of the head in the classification of aphids. Three types or 
lines of modifications may be distinguished. First, the transverse 
(generalized), in which the head is broader than long, the distance 
between the antennae is wide and the frontal margin straight; this 
form is characteristic of the Lachnina. Second, the subquadrate 
(aphidian), in which the head is narrowed anteriorly and produced as 
a pair of frontal tubercles on which the antennae are situated; the 
frontal margin is concave or emarginated. Third, the reduced (pem- 
phigian), correlated with the reduction of the antennae and the eyes 
in the gall and underground forms of the Pemphiginae. The frontal 
margin in this type is usually convex. The family is unique, as far 
as known, in the presence of three types of insect eyes at the same 
time in the alate forms: the larval eyes which persist through life as 
the ocular tubercles with the compound eyes and the dorsal ocelli of 
the alate forms. The antennae are typically composed of six segments. 
The first two segments are short and broad, and usually devoid of 
sense structures. The following segments are more slender and known 
as the flagellum, and always provided with special sense structures as 
sensilla and sensoria. The terminal segment is characterized by the 
presence of a primary sensorium at the apex of the segment, and the 
prolongation of the segment beyond the sensorium as a slender filament, 
known as the spur, which carries a group of sensilla on the distal end, 
very constant and characteristic of the family. The subterminal seg- 
ment is also provided with one of the primary sensoria near its apex. 
Various types of sensilla (sense hairs) are present on the anten- 
nae which have considerable taxonomic value and may be distinguished 
under the following heads: First, the long and slender hair-like sen- 
silla of the flagellum as present in the Lachnina and related tribes. 
Second, the short,and spine-like sensilla of the Aphidini. Third, the 
glandular sensilla with enlarged apices of the Macrosiphini. Fourth, 
the apical sensilla of the spur just referred to. The sensoria (sense 
membranes) are of many kinds and very characteristic of the family. 
The following types may be recognized: First, the reticulations or 
