LEAF-INSECTS 



269 



that the spectrum exhibits slight distinctions from that of solu- 

 tions of chlorophyll, but does not differ from that of living 

 leaves. Mr. J. J. Lister when in the Seychelles brought 

 away living specimens of Phyllium ; and these becoming short 

 of food, nibbled pieces out of one another just as they might 

 have done out of leaves. The Phasmidae are purely vegetable 

 feeders, and these specimens did not seriously injure one another, 

 but confined their depredations to the leaf-like appendages and 

 expansions. 



The males of this genus are totally different from the females ; 

 the foliaceous tegmina being replaced by appendages that are not 

 leaf-like, while the posterior wings, which are large and conspicu- 

 ous parts of the body, have no leaf-like appearance (Fig. 155). 



In the female Phyllium the hind wings are not present, 

 being represented by a minute process (Fig. 156, B). The 

 tegmen of the female Phyllium is, from various points of view, 

 a remarkable and exceptional structure. It is the rule that 

 when there is in Insects a difference between the alar organs of 

 the two sexes it is the male that has them largest ; this is the 

 case in Phyllium so far as the hind wings are concerned, but in 

 the fore- wings the rule is departed from, the leaf-like tegmina of 

 the female being very much larger than the rudimentary wing- 

 covers of the male. In Phasmidae it is the rule that the tegmina 

 are atrophied, even when the hind wings are largely developed. 

 This is the case in the male of Phyllium, but in the female this 

 normal condition is re- 

 versed. Although the alar 

 organs of Phasmidae have 

 received hitherto but a small 

 amount of attention, it is 

 probable that the female 

 tegmen of Phyllium is as 

 peculiar morphologically as 

 it is in other respects. In 

 Fig. 156 we give an accur- 

 ate representation of the 

 chief nervures in the teg- 

 men of a female P. cruri- 

 foliurn. It is interesting to compare this with the diagrams we 

 give of the tegmina of a Blattid (Fig. 121) and of an Acridiid 



FIG. 156. Alar organs and one side of thorax of 

 Phyllium crurifolium : A, tegmen ; B, rudi- 

 ment of wing ; C, pronotum ; D, anterior 

 division of mesonotum ; E, posterior division ; 

 F, metanotum ; a, b, c, d, e, chief \ving- 

 nervures ; a, mediastmal ; I, radial ; c, uluar ; 

 d, dividens ? ; e, plicata ? . 



