DESCRIPTIONS IN THE FAMILY APHIDLD^E. 163 



first colonizes the grape its honey tubes elongate and its form partakes 

 of the genus Macrosiphum. This same aphis when it colonizes the 

 plum in early spring appears like the genus Myzus. Thus we see 

 that a change of host plant affects not only the characteristics of a 

 species but also those of the genus. 



Now, if we depend upon the early system of description we may 

 have one species described as many species and contained in more than 

 one genus. One remedy is to follow a single species through its 

 entire seasonal history and obtain the specific names of all its host 

 plants, with descriptions of it containing all its changes in color and 

 form. By doing this one-form method will be discarded with sev- 

 eral troublesome synonyms. 



Another remedy will be found in a " host plant catalogue," which 

 should contain all the scientific names of the plants, each followed 

 by the species affecting it. The former is not only a list of beneficial 

 or injurious plants which are affected by these insects, but it is also 

 a good index key for identifying them. For instance, if a colony is 

 found infesting okra {Hibiscus esculentus) there may be but little 

 difficulty in identifying the species, because by looking into a late 

 host plant catalogue for Hibiscus esculentus there will be found Aphis 

 gossypii Glov. and Rhopalosiphum dianthi Schrank. Then by coin- 

 paring the descriptions of these species with the one in question an 

 identification is sure to follow unless it is a new species to the plant in 

 question. If the latter is true, a record of it should be made. 



Another item of importance in this connection is the date or dates 

 when a certain species is found to colonize a particular host plant. 

 This is essential, since we might get several species from one form 

 like Callipterus walshii Monell. The latter in July is frequently 

 found with a mottled pulverulence on its body. In October it can be 

 found with an .entirely different coloration, consisting of no pulveru- 

 lence, but with a background of brown color marked with dark spots 

 and transverse bars. If the dates for these colorations or character- 

 istics are given, the possibility of giving this species other names than 

 its own can be eliminated. 



Now, what is the bearing of an incomplete description upon 

 methods of eradication? A conspicuous example in Texas is the 

 "green bug 1 ' (Toxoptera graminum Rond). Whenever the natural 

 conditions permit this aphis to flourish it can devastate all the wheat 

 and oats that may be planted in its latitude of infestation. The 

 financial losses are almost inconceivable. With the present incom- 

 plete life-history knowledge of this pest no artificial method of 

 eradication seems possible. The only thing that can be depended on 

 with any degree of success until the life history is known will be the 

 inimical insects which prey upon it. 



