WALKING-STICKS AND WALKING-LEAVES. 71 



the male of Phyllium, but the female offers precisely 

 the opposite character — the wing-covers, the only 

 members susceptible of such exact mimicry of a leaf, 

 being greatly developed, while the wings are aborted. 

 There is this to be pointed out, that had the wings, and 

 not the tegmina, been made to resemble a leaf, the 

 mesothorax would have remained entirely visible ; it 

 would have spoilt the perfection of the resemblance of 

 the insect and a leaf, by forming with the head and 

 prothorax a petiole, as it were, too large, and too 

 apparent. Nature has then, contrary to the general 

 rule, atrophied the wings and developed the tegmina, 

 to obtain the appearance of a leaf over the largest 

 surface of the body possible. The great reduction of 

 size of the prothorax and antennee, parts which would 

 equally interfere with the resemblance, is likewise to be 

 included in this artifice, tending to the same end. 



Another surprising thing — it is probable that the 

 female tegmen of Phyllium is a structure as peculiar 

 morphologically as it is in other respects. In order the 

 better to imitate a leaf, the radial vein is placed quite 

 close to the posterior edge, permitting the radial veins 

 of the tegmina, when they come together, to juxtapose, 

 typifying the principal nerve or mid-rib of a leaf. The 

 lateral ribs of the leaf are represented exactly by 

 the oblique costal veins. It will thus be plain, that 

 the tegmina of female Phyllium not only break a rule 



