4 E- Takabaslii. 



(1) The aphids arc abundant in Rpecies and individuals. 



(2) Most species an inactive or sedentary, being decidedly gregarious in 

 habit, and congregate on the surface of the leaves or branches of plants. 



It is obvious that the larvae of some Diptera (Syrphidae, Leucopis, CJdoro- 

 pisca, ApMdoletes) and a few Lepidoptera (Taraka Jmmada Druce, etc.) can 

 capture only such inactive insects. Some Callipterina are rather sporadic, having 

 a habit of jumping from the host and hence their enemies are fewer. The 

 enemies of Gfreenidea seem to he very few. This is perhaps due to the rather 

 active habit of this aphid. The species in galls are usually protected from 

 predacious or parasitic enemies. 



(3) The aphids are mostly weak, delicate and appetizing, and any predatory 

 insects or spiders are easily able to eat them. 



(4) The aphids are viviparous for a long period from spring to autumn 

 (in the tropics they are viviparous throughout the year), supplying a continual 

 food source for the predatory insects. Davis has found that the length of the 

 various stages id' Phyllophaga has a. direct relation to the number of enemies in 

 each stage (Bull. Illinois Dept. Registration and Education, Div. Nat. Hist. 

 Survey, XIII, 5) 



The number of aphids in the field also depends to a great extent upon 

 various inorganic influences, they being killed mechanically by rains, winds, etc. 

 It is needless to say that these defenceless, delicate creitures maintain their 

 existence only by the extraordinary powers of multiplication given to them by 

 parthenogenesis, viviparity and rapid growth. The prominent fluctuation of the 

 numbers of aphid individuals in the Held is apparently due to the two peculiar 

 features rapid multiplication and defenceless characters — of these animals. 



The predominant natural enemies id' insects are always other insects. The 

 aphids are subject to attacks of abundant enemies, most of which are, of course, 

 insects. 



(Orthoptera) Mantidae. Oecanthus, Xiphidium, Camptonotus, etc. have been 



recorded by various investigators to eat the aphids. In Formosa. Mantidae are 

 sometimes found to prey upon various species of these insects. 



(Rhynchota) The predatory specie* of Miridae, Hebridae, Reduviidae and 

 Pentatomidae each are known to eat aphids. No Rhynch da have been noticed 

 eating aphids in Formosa. 



(Neuroptera) The insects included in Chrysopidae and He merobiidae destroy 



