MIMICRY AMONGST THE BLATTIDJE. 301 



In a very superficial sort of way cockroaches and beetles may 

 l>c said to be similarly constructed. In both the pronotum is 

 large whilst the other thoracic tergites (in the winged species) 

 are concealed; in both the membranous wings are covered b\ 

 elytra or tegmina of a coriaceous or corneous texture. In fact 

 only a slight modification of the cockroach-form is required to 

 producea distinctly < !oleopterous appearance. The names lycoides, 

 buprestoides, coccinelloides, dytiscoides, silphoides, given to species 

 of Blattidae by various authors, are sufficient evidence of their 

 resemblance to beetles. It is quite an open question whether 

 this generalised resemblance of certain Blattidse to Coleoptera 

 can be legitimately classified under the heading of Mimicry. It 

 could well be argued thai some of the species, at any rate, owe 

 their beetle-like form to convergence in development, or, to us,! 

 Sir Ray Lankester's term, that cockroaches and beetles arc homo- 

 plastic forms. On the other hand, as will be seen later, some of 

 the cases of resemblance are so detailed and close that it is 

 impossible to regard them as anything but examples of true 

 mimicry, and it becomes most difficult to draw the line between 

 the two classes . >f resemblance. For convenience' sake, at any 

 rate, throughout this paper the Blattidaa which resemble insects 

 of other orders \\ ill be termed " mimics." 



Examples of generalised mimics of t he ( loleoptera are furnished 

 by species of Pachnepteryx Br., < ',,,'<„',/, </!(/ Sauss., Paratropes 

 Serv., Phoraspis Serv., Evstegasta Gerst., Achroblatta Sauss., 

 Corydia Serv., Areolaria Br., and Hypnorna Stal, whilsl several 

 species in other less specialised genera might be quoted, of not. 

 one of these species can it he said I li.it it, is very like any definite 

 species of beetle. Eustegasta buprestoides Walk., from West 

 Africa, is a metallic green cockroach with round yellow spots on 

 the tegmina, and as its name implies, if is very like a Buprestid 

 beetle. But in spite of the most diligenl search amongst col- 

 lections of Buprestidae, I have never found a species which by 

 the greatest stretch of imagination could be regarded as even an 

 indifferenl model for the cockroach. 



Belt speaks of mimetic cockroaches in 'The Naturalist in 

 Nicaragua' as follows : — " The phosphorescenl species of Lam- 

 pyridae, the fireflies, so numerous in Tropical America, are 

 equally* distasteful, and are also much mimicked by other 

 insects. 1 found different species of cockroaches so much like 

 them in shape and colour that they could not he distinguished 

 without examination. These cockroaches, instead of hiding in 

 crevices and under logs like their brethren, resl during the day 

 exposed on the surface of leaves, in the same manner as the 

 fireflies they mimic" t. It was with much interest that ] 

 found in the Hope Museum, Oxford, a specimen of the cock- 

 roach Achroblatta lateola Blanch., with the following note in 



* T. e. with the non-phosphorescent species, by which licit appears to mean the 

 beetles now known us Lycidae. 

 t 1 quote from the liveryman's Library Edition (Dent A Sons, lull), p. 243. 



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