Mr. F. WalkeFs Descriptions 0 / 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, Muller, Nageli and many other authors, 
agree that spores, pollen and embryos are produced by free cell- 
formation from nuclei. 
XL VII. — Descriptions 0/ 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 JuglandiSj Frisch. 
Aphis Juglandis, Frisch, Ins. xi. pi. 16. f. I, 5. 
Lachnus Juglandis j 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 
* Zeitsdirifl fur Wiss. Botanik, Heft 3, 1847. f Z. cit. 
