MIMlCUy AMONGST THE BLATTIU.E. 361 



In a very supei-ticial sort of way cockroaches nnd beetles may 

 be said to be similarly constructed. In both the pronotum is 

 Urge whilst the otlier thoracic tergites (in the winged species) 

 are concealed ; in both the membranous wings are covered by 

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

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

 produce a distinctly Coleopterous appearance. The names lycoides, 

 hn.prestoides. coccinelloules, di/tiscoides, silphoides, given to species 

 of lilattida; by various authors, are sufficient evidence of their 

 resemblance to beetles. It is quite an open question whether 

 this generalised resemblance of certain Blattidfe to Coleoptera 

 can be legitimately classified under the heading of Mimicry. It 

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

 their beetle-like form to convergence in development, or, to use 

 Sir Ray Lankester's term, that cockroaches and beetles are 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 time 

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

 the two classes of reseml)lance. For convenience' sake, at any 

 rate, throughout this paper the Blattidas which resemble insects 

 of other orders will be termed " mimics." 



Examples of generalised mimics of the Coleoptera are furnished 

 by species of Pachnepteryx Br., Calohlatta Sauss., Paratropes 

 Serv., Phoraspis Berv., Kxistegasta Cerst., Achroklatta Sauss., 

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

 species in other less specialised genera might be quoted. Of not 

 one of these species can it be safd that it is very like any definite 

 species of beetle. _ Eiistegasta hiiprestoides Walk., from West 

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

 the tegmina, and as its name imj^lies, it is very like a Buprestid 

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

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

 the greatest stretch of imagination could be regarded as even an 

 inditterent model for the cockroach. 



Belt speaks of mimetic cockroaches in ' The Naturalist in 

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

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

 equally* distasteful, and are also much mimicked by other 

 insects. I found different species of cockroaches so much like 

 them in shape and colour that they could not be distinguished 

 without examination. These cockroaches, instead of hiding in 

 crevices and under logs like their brethren, rest 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 I 

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

 roach AchroUatta lateola Blanch., with the following note in 



* I. e. with the non-phosphorescent species, by which Belt appears to mean the 

 heetles now known as Lycidae. 

 t I quote from the Everyman's Library Edition (Dent & Sons, 1911), p. 213. 



