362 MR. ROBERT SHELFORD ON 



WestwoocVs handwriting attached to it : — " This Blatta lives on 

 trees and closely resembles in its habits some of the large Lam- 

 pyridae [T. Belt]." This is doubtless one of the species mentioned 

 by Belt in his book, and I had great hopes of being able to match 

 it with a definite species of Lampyrid beetle, but the most diligent 

 search through the Godman-Salvin collections of Central American 

 insects failed to reveal a " model " to the cockroach. The Malaco- 

 dermatous appearance is undoubtedly but generalised, not specific. 

 The same may be said of Hypnorna amoena Sauss. & Z., also from 

 Central America. This Blattid has all the appearance of a small 

 Longicorn, but it actually resembles no particular species of that 

 family. It may, of course, be argued that further collecting will 

 bring to light species of beetles which can legitimately be regarded 

 as models to the cockroaches, but I do not think that this is in 

 the least degree probable. Our knowledge of the Central American 

 Coleoptera must now be nearly complete, speaking from the point 

 of view of the systematist, aiid the West African Eustegasta Im- 

 prestoides is so very abundant that it might reasonably be expected 

 that its supposed model would be, if not abundant, at any rate in 

 sufl&cient numbers to permit of some specimens falling into the 

 hands of collectors. At the very end of this paper I desciibe 

 two new species of Blattid?e, belonging to a new genus, wdiich 

 also must fall into the category of generalised Coleopterous 

 mimics. 



The two species of the Oriental genus ThyrsoGera Burm. are 

 shining black cockroaches with large yellow spots on the tegmina, 

 a type of coloration frequently met with amongst the Endomy- 

 cliidfe of the same region. These cockroaches, though far larger 

 than, and in other jDoints quite unlike any Endomychidse known 

 to science, may possibly be regarded as part of a " convergent 

 group," the dominant or " central " members of which are the 

 yellow-spotted Endomychidse (genus Eumorphus). A generalised 

 resemblance to certain families of Rhynchota is also shown by 

 some Blattidte. For example, some species of Holocompsa Burm. 

 and Hypercomj^sa Jieheri Br. are rather like small Capsidse ; the 

 illusory effect is produced by the tegmina, which are largely 

 membranous and hyaline, though opaque and coriaceous at the 

 base; the I'esemblance does not bear a very close examination. 

 Homopteroidjea nigra Shelf, is not unlike some small Fulgorid or 

 Jassid. Mr. J. C. Kershaw found at Hong-Kong, under a stone, 

 several little black Pentatomids, and in company with these a 

 similarly coloured and shaped cockroach which appears to be 

 identical with PseudopJiyllodromia parilis Walk., and he sug- 

 gested * that the cockroach mimics the bug. Having seen the 

 specimens I pi-efer to regard them as examples of syncryptism or 

 of homoplasy. 



Linnaeus, deceived by the Coleopterous appeaiance of Corydia 

 petiveranaj placed it in his genus Cassida. Mr. T. Bainbrigge 



* 111 a letter to Profe.s'ior Poulton. 



