22 



Buckton gives an interesting account of the dimorplaic form* 

 illustrated by drawings.! 



He describes and depicts the curious appearance of the dorsum, 

 " tessellated like the carapace of a tortoise." I have, however, 

 failed to discern outlines of these plates on the upper part of the 

 dorsal region as shown in his figure, and I have not therefore drawn 

 them in my own. 



From an examination of many specimens I find the number of 

 transparent leaflets or folioles on the margins of the flattened 

 abdomen and anal plate to be twenty. 



On the head eight, besides a small narrow one on the base of each 

 antenna. 



On the outer margin of each tibife of the first pair of legs, eight 

 or nine, and two en the tarsus. 



On the third pair of legs these appendages are not foliaceous but 

 are reduced to long triangular, almost linear hairs. 



The tarsi of all the legs are terminated by two claws. 



The folioles on the head and abdomen are orbicular, those on the 

 bases of the antennae and on the legs are narrowly ovate and acute. 



Buckton states that " each foliole contains a radiating system of 

 vessels, which Signoret regards as ramifying nerves." 



The generative organs appear to remain extremely rudimentary 

 and indistinct, and since the insect rarely exerts itself by movement 

 of any kind during the three or four months of its existence, it is at 

 present impossible to imagine what use this dimorphic form can be 

 to the species. 



Balbiani and Signoret asserted that the insect neither moults nor 

 undergoes any metamorphosis whatever. Buckton, on the contrary, 

 states that he had clear proof that the skin was occasionally shed, 

 and that he possessed casts complete, even to the folioles or 

 flabellae. 



Moreover, he says, " I have every reason to believe that when 

 such moults occur the insect emerges without folioles, such organs 

 being replaced by tufts of hair." In plate Ixxix. he figures a speci- 

 men found so close to the slough (also figured) that he had no 

 doubt it emerged from it. 



In this figure the foholes are no longer present as such, but are 

 reduced to hairs, and the appearance of this instar is now extremely 

 similar to that of the normal young larva. 



According to Balbiani and Signoret, the green viviparous female 

 is the parent of the dimorph ; but Buckton figured a black variety 

 of the apterous viviparous female, which he tells us "yielded on 

 dissection, June 25ch, nine young, which unmistakeably showed 

 they were of the abnormal kind." He adds, "several of the pseiido- 

 morphic young were, moreover, scattered on the same leaf which 

 supported the aphis, and I conclude were born of her." 



* " lirit. Aphides," vol. ii., pp. 126-133. 

 t PI. Ixxix. 



