Mr. F. Walker's Notes on Aphides. 61 



read, are one by Dr. Richardson (Phil. Trans.), and one by W. 

 Curtis (Linn. Trans.) As far as I have remarked, the obser- 

 vations of the writer in the Phil. Trans., which you quote, are 

 correct in regard to several species. I have never seen a male 

 pairing with a winged female, but Mr. Hardy, an entomologist of 

 Newcastle, informed me last year that he had observed such to 

 be the case with one species, and I have no doubt of his accuracy. 

 In one species {A. Saliceti), the wingless and winged broods of 

 females are alternate, but in June wingless oviparous females 

 appeared differing much in structure from their viviparous rela- 

 tions, and accompanied by wingless males, with which they paired. 

 A. juglandicola, a pretty little yellow or orange species on the 

 walnut, is also remarkable ; the female has continued viviparizing 

 for the last six weeks, but a short time ago the male suddenly 

 appeared, and after a few days passed away ; it was accompanied 

 by a variety of the female, but I did not observe that they paired. 

 I cannot say that 1 have seen this year any periodical flight of 

 Aphides, but I do not believe that it was confined to one day nor 

 to one species, the bean Aphis. Last year I distinctly remarked 

 two large flights or migrations of several species ; the first in the 

 middle of May, the second in the middle of September ; they 

 both occurred on still fine warm days, and I think that the flight 

 of Aphides is too passive and feeble to allow their migrations 

 from a long distance. In most species, where the generations are 

 alternate, the winged females migrate as soon as their wings are 

 fully developed and dry, and the chief object of such flights is to 

 place their wingless young ones in possession of fresh pastures, 

 and their existence soon ceases when this purpose is accomplished. 

 Do you think that a comparison of the analysis of different plants 

 would enable us to discover why Aphides prefer some to others in 

 their migrations ? A. Rosce migrates from the rose to the teazle, 

 another species from the rose to the blades of corn and grasses, 

 a third from the rose to the columbine, a fourth from the willow 

 to umbelliferous plants, &c. Are their correspondencies in the 

 respective proportions of the constituent parts of these plants ? 

 I remain, my dear Sir, yours sincerely, 



Francis Walker. 



