Mr. P. Walker's Descriptions of Aphides. 443 



I may add to the above, in conclusion, that the opinions of 

 observers are becoming more and more in favour of the view, that 

 multiplication by cell-division is the regular mode of increase in 

 vegetating or growing parts. Nageli* asserts it in his most re- 

 cent publications, and Unger f considers that it is the mode of 

 increase in the cambium layer or growing region of wood. On 

 the other hand, Mohl, Miiller, Nageli and many other authors, 

 agree that spores, pollen and embryos are produced by free cell- 

 formation from nuclei. 



XLVII. — Descriptions of Aphides. By Francis Walker, 



F.L.S. 



[Continued from p. 345.] 



Eighth Group. 



The following species is one of the most beautiful of the Bri- 

 tish Aphides, and is distinguished from all other kinds by its 

 peculiar structure. 



17. Aphis Juglandis, Frisch. 



Aphis Juglandis, Frisch, Ins. xi. pi. 16. f. 1, 5. 



Lachnus Juglandis, Kalt. Mon. Pflan. i. 150. 3. 



The viviparous winged female. It feeds from July to October 

 on the leaves of the walnut, Juglans regia, and is stationed in 

 clusters along the middle vein of the upper side of the leaf. The 

 body is pale orange : the head is darker, and rather short and 

 broad : the front forms an angle where it retreats on each side, 

 and is slightly concave in the middle : the feelers are filiform, and 

 a little more than one-fourth, or sometimes full one-third, of the 

 length of the body ; the fourth joint is much less than half the 

 length of the third ; the fifth is a little shorter than the fourth ; 

 the sixth is less than half the length of the fifth ; the seventh is 

 much shorter and more slender than the sixth ; the tips of these 

 joints are black : the eyes are red : the mouth reaches to the mid- 

 dle hips ; its tip is black : the discs of the chest and of the breast 

 are black : the sides of the fore-chest are notched : the abdomen 

 is rather large, and sometimes it contains upwards of thirty young 

 ones which are all of the same size : the nectaries are extremely 

 short, and less than one-twentieth of the length of the body: in the 

 pupa there are four rows of brown spots along the back of the 

 abdomen ; the middle rows, which are confluent in the winged 

 insect, have a short and slender transverse brown line on each 

 interval between the spots : the fore-legs are much shorter than 



* Zcitscliril't fur Wiss. Botanik, Heft 3, 1847. f L. cit. 



