DIMORPHISM IN CHAITOPHORUS ACEEIS. 129 



on tlie occiput. Thorax not visibly separated from 

 the head. Abdomen broad, oval ; dorsum and sides 

 decorated with four rows of plates or pseudo-scales, 

 which gives the insect a somewhat tessellated appear- 

 ance, and so may be likened to the carapace of a tor- 

 toise. Cauda and anal plate very minute. 



The legs are short and much flattened. This dila- 

 tation appears most strongly in the tibice, whose 

 margins are sharply serrated. 



But the most remarkable part of the insect is the 

 development of the tegumentary system. Instead of 

 the hairs seen in the normal young, the body and 

 limbs are furnished with a series of flat transparent 

 leaflets, which surround the front, the abdominal 

 margin, and the outer edges of the tibiae. Each 

 foliole contains a radiating system of vessels (?), which 

 Signoret regards as ramifying nerves. Folioles also 

 are attached to the first joints of the antennas, which 

 are gibbous, and elongated folioles also sprout from 

 tubercles near the anus. 



The tarsi have, in addition to the usual double claw, 

 two minute hairs, the summits of which are expanded 

 into sucking discs or pulvilli. In this and some other 

 respects, the insect somewhat approximates to the 

 genus Phylloxera. There are only five joints to the 

 antennae. The rostrum is short and very stout. 



When placed on a slip of glass under a low mag- 

 nifying power it moves, but with extreme deliberation. 

 Its progression is ludicrous, poising itself on its hind 

 legs, and employing its pulvilli to secure its position 

 before it attempts to make any further advance. 



Its habits are quite solitary, strongly fixing itself to 

 the inner angles of the leaf-ribs of the sycamore or 

 maple, on which they appear as small yellow scales. 

 These may be easily detected if the leaf be examined 

 by the transmitted light of the sky. 



On account of the transparence of this insect, a 

 slow peristaltic movement of the internal organs may 

 be often noticed, and under favorable circumstances 



VOL. II. 9 



