ation) may be winged or wingless, or both forms may occur; they 

 reproduce agamicalh', some species Ijeing oviparous and depositing 

 pseudoova, or eggs which do not require fertilization for develop- 

 ment; while others are viviparous and bring forth young alive, the 

 pseudoova developing within the bod}^ of the parent. There may be 

 a succession of generations produced agamically, with most species 

 this mode of reproduction continuing until the approach of autumn, 

 when the true sexes appear and deposit eggs; or a species may be 

 more oy less biennial, some individuals producing true sexes only every 

 second j^ear. With still other species, the true sexes of which are at 

 present unknown, agamic reproduction possibh' continues for a series 

 of years. The same species of aphide may present several forms, as 

 wingless agamie females, winged agamic females, and the true sexual 

 forms; in the last the male may be winged and the female wing- 

 less, or both sexes may be wingless. The diti'erent generations of a 

 given species may vary more or less, and in some instances this is the 

 case to such an extent that thej^ appear to belong to distinct species. 

 Aphides are enabled to increase with great rapidity by reason of the 

 short time required by their young to reach maturity. Their powers 

 of multiplication are so great that if unchecked the product of a 

 single insect during one season would run up into the ])illions. Very 

 fortunately, however, there are many drawbacks to their increase, 

 among which are certain weather conditions, parasitic and predaceous 

 insects, and fungous diseases. When one or more of these agencies 

 are in abeyance, aphides may become very numerous and destructive 

 locally or over a considerable range of territory. 



THE EUROPEAN GRAIN APHIS. 



{Siphocorijne cu'etuc Fab.) 



The European grain aphis (fig. 2) is the common greenish apple aphis 

 of the United States, and is the species erroneously considered by Fitch 

 as identical with the European Aphis mali Fab., by which name until 

 recently it has been very generally known in our literature. Two 

 species, however, have been confused under this name, the present 

 and the following, which fact was recognized by Mr. Th. Pergande, 

 and also by Dr. J. B. Smith. Prof. E. D. Sanderson in 1902 described 

 this insect as new under the name of Aj?/u's fiicAi^ but Pergande has sub- 

 sequently shown that the insect is identical with the European grain 

 aphis {Aj)his avenEe Fab.), and considers that the species really belongs 

 to the genus Slpliocoryne of Passerini. This species is recorded from 

 various widely separated localities, and is probablv very generallv 

 distributed throughout the United States. Twenty-two plants upon 

 which it has been observed are recorded, comprising eight trees, four 

 weeds or herbs, and ten grains and grasses. Of orchard fruits, apple, 

 pear, quince, and plum are food-plants; and of grains, rye, oats, and 



[Cir.81] 



