4 E. Takahashi 



diffcreuces Ijctwecn the young and fuUy-growu nymphs are more disthict than 

 those between the latter and the adults, especially so in the apterous forms. 



Each of the nymphal instars usually displays structural characters sufficient 

 for the identification of the particular insfar that it represents, but the third and 

 fourth instars of the apterous form are scarcely difl'erent in structure in (rrecnidca, 

 Dilachius and Shivaphis celti Das. 



(Aleyrodiform femaks ,of Hormaphidina) 



Since tlie metamorphosis ot the aleyrodiform females of some genera of 

 Hormaphidina, as .Isfegojjtcri/x, UamamcUstcs and Iloniiaphiti, is very peculiar, 

 it will be considered first. 



The adults are very hard-bodied, almost black and aleyrodiform, being 

 cemented to their liosts. In the first instar, the nymphs are active, crawling over 

 the host. The)' are pale in colour, since the impregnation of chitin is much lighter 

 than in the adult, and arc provided with well-developed legs and antennae, the 

 latter 3 or 4- jointed. In the second instar, they become stationary, with the 

 antennae rudimentary, 2 or 3-jointed; the front and middle pairs of legs without 

 tarsi; the hiud legs provided with one-jointed tarsi, without claws. In the third or 

 last instar, the body becomes broader, tlie antennae more rudimentary, the legs 

 remaining almost as in the preceding instar. This metamorphosis resembles that of 

 some female Coccidae. 



(Other Aphidinae) 



In the young nymphs, the body is often rather flattened, witli tlie abilonien 

 narrow. In the dimorphs or the first instar specialized tor aestivation of Fvri- 

 phyllus, it is quite depressed and thin. 



In proportion to the size of body, the head is larger in the young nymplis 

 than in the grown ones or adults. It is completely fused with the pronotum in 

 Ccrataphis, Oregma, Astegopteri/x. Aleurodaphis, Cervaphis, Neophyll aphis, Grec- 

 ufdca and others, except in the fully grown nymphs and adults of the winged form. 

 The dorsal surface of the head of Lavhnus or Eulachnus is divided, though not 

 distinctly so, by a longitudinal line, visible even in the first instar. In the nymphs 

 of NeophijUaphis podocaipi Takah., it is likewise divided, though scarcely so in the 

 adults. In Oregma and CrmUiplus. a pair of horns is present on tlie front, even 

 in tlie first instar. 



They are usually larger in the nymphal stages than in tlu^ winged adults. 

 In Oregma huinhusi/oliuc Takah., tlie apices of these horns are rather pointed in the 



