TRIBES OF APHIDIDAE 51 
(folicola) feeding on the tender twigs and leaves of trees and woody 
plants. Fourth, those feeding on annual plants (herbicola), which un- 
doubtedly represent the latest type of development in the direction 
of food habitat. 
KEY TO THE SUBFAMILIES OF THE APHIDIDAE 
1. Typical Aphididae in which the aphidian characters are usually expressed by 
increase or additions, as seen in the development of the spur and sensoria of the 
antennae; and in the great development of the cornicles and cauda. The group is 
typically aerial in habitat. .. . Subfamily APHIDINAE 
—Specialized Aphididae in which the typical aphidian characters are specialized 
in the line of reduction or loss, as seen in the number of segments to the antennae, 
in the spur, sensilla and sensoria; in the reduction or loss of the cornicles and cauda ; 
reduction in venation is also carried further in this group than in the preceding. 
The group is typically subterraneous or protected in habitat, as found in folds of 
leaves, in crevices of bark, or in galls. Positive pemphigian characters are seen in 
the great development of dermal glands. . . . Subfamily PEMPHIGINAE 
SuBFAMILY APHIDINAE 
Retzius, 1783, DeGeer’s Genera. Sub “Fam. I. Abdomen corniculatum.” 
Latreille, 1807, Gen. Crust. Vol. 38. Sub Bicorniculatum et bituberculatum. 
Leach, 1818, Trans, Hort. Soe. Vol. 2 Sub Eriosoma (genus). 
Burmeister, 1835, Handb. Entom. Vol. 2. Sub Lachnus (genus). 
Koch, 1854, Die Pflanzenl. Heft 1. Sub Dikyphonen et Monokyphonen. 
Passerini, 1863 Aphid. Ital. Sub Aphidinae et Lachninae (subfamilies). 
Buckton, 1876, Monogr. Vol. 1. Sub Aphidinae (subfamily). 
The subfamily Aphidinae was foreshadowed by Retzius (1783) 
and Latreille (1807) in their grouping of the species of the genus 
Aphis. Leach (1818) first indicated the Pemphiginae by the genus 
Eriosoma, restricting the genus Aphis as representative of the present 
subfamily. Burmeister further divided the genus by erecting the genus 
Lachnus which became the foundation of Passerini’s subfamily 
Lachninae. Koch (1854) indicated the subfamily names Dikyphonen 
and Monokyphonen, both of which are nomena nuda. Buckton (1876) 
united Lachninae with Aphidinae which is now generally taken as the 
natural limits of the subfamily. 
Morphological characters. Vhe positive characters of the sub- 
family are seen in the gradual increase or direct development of the 
antennae and the spur, the sensilla and sensoria, and the cornicles 
and cauda. The Pemphiginae, on the other hand, show a non-develop- 
ment or reduction and loss of the same characters. 
Biological characters. Three distinct stages or steps of food 
habitat may be distinguished in the present subfamily. First, those 
feeding on woody part of trees, which is undoubtedly the primitive 
food-habitat of the family. This is characteristic of the Lachnina and 
the more generalized Chaitophorina. Second, those feeding on tender 
