372 Mr. F. Walker on the Migrations of Aphides. 



Fig. 6. Brachiolit.es racemosus : the right-hand portion shows the form of the 

 arms as seen on outside of flint ; the left-hand portion shows the 

 root and longitudinal sections of several arms, p. 364. 



— 7. Brachiolites tubulatus, p. 366. 



PI. XVI. (all in chalk). 



Fig. 1. Brachiolites foliaceus : the lower part showing the outside, the upper 

 part a vertical section, p. 364. 



— 2. Brachiolites digitatus, p. 365. 



— 3. Brachiolites fenestratus, p. 367. 



— 4. Brachiolites labrosus, p. 368. 



— "/. Brachiolites protemus, p. i)69. 



XLI. — Remarks on the Migrations of Aphides. 

 By Francis Walker, F.L.S. 



From the great Author all that lives 

 Its stated boon of life receives. 



Ere long again restored to thee ; 

 Each insect too minute to name 

 Yet owns a portion of thy flame, 



Part of thy numerous family. 



Resplendent cars of fiery glow 

 From realms of light to earth below 



Thy animated offspring bear ; 

 And when this mortal trial ends, 

 Again the glorious car attends 



To wing them to their native sphere. 



Lorenzo de Medici. 



In the following notice I have enumerated some of the species 

 of Aphis that migrate at regular periods from one kind of plant 

 to another, or whose food has been partly altered by the cultiva- 

 tion of plants. Aphis Rosce migrates from the rose to the teazel ; 

 A. dirhoda from the rose to grasses and flags, and the introduc- 

 tion and growth of corn have afforded it a new nourishment, and 

 have consequently modified its habits ; and the cultivation of va- 

 rious species of rose brought into this country has also increased 

 its food, and that of A. Rosce and of the three following species : 

 A. trirhoda migrates from the rose to the columbine, and this 

 change of food is probably not aboriginal, but consequent on the 

 cultivation of the latter plant. A. tetrarhoda and A. Rosarum 

 appear to live only on the rose genus. A. Avence has its first 

 habitation on grasses, and the cultivation of corn has furnished 

 it with a new and abundant source of food. A. Caprece migrates 

 from the willow to umbelliferous plants, and in this case both 

 the winter residence and the summer pasture of the species are 

 aboriginal. The food of A. Urticaria is divided between the 

 nettle and the bramble, and both these plants are also original 

 sources. A. Humuli lives permanently and aboriginally on the 



