LEAF INSECTS 61 



considerable variations as are met with in leaf- 

 like Lepidoptera and Orthoptera, from genera- 

 tion to generation, is a standing witness against 

 the truth of " Darwinism," inasmuch as, accord- 

 ing to the Darwinian theory, such variations 

 ought either to become fixed by natural selection 

 or swamped by interbreeding. On the face of 

 it there would seem to be some force in this 

 argument. Whatever the answer may be, it is 

 not that these varieties may become fixed in 

 course of time ; on the other hand, it may be that 

 natural selection is interested in keeping alive the 

 variations for the benefit of the species, not for 

 the production of new species. In any case it is 

 a good point, worthy of special consideration. 



Butterflies owe their leaf-like appearance to 

 the effect of bilateral compression when the 

 wings are closed. Leaf insects of the genus 

 Phyllium, which belong to the order Orthoptera 

 (containing also the cockroaches, grasshoppers, 

 and stick-insects), owe it to the dorsiventral 

 flattening of the body. A similar antagonistic 

 flattening of the body occurs between two 

 human ectoparasites where the compression 

 also achieves a cryptic object indirectly, viz. : 

 the bilaterally flattened Pulex and the dorsiven- 

 t rally flattened Cimex. 



An excellent description and plate of Phyllium 

 crurifolium, a wonderful leaf insect which is 

 found in the Seychelles islands as well as in 

 Ceylon, has been published recently by Mr 



