Tneecta. 269 



lity in dit'ferent years; (III) tlie extent to which cT suvvive tlie wiiiter probably 

 varies; (IV) tlie percentage of cT is perhaps greater in small irflands; (V) it is 

 improbable that tbe nature of soil and Vegetation, or altitude, affect the pro- 

 portions of <S and $. Tbe writer bas found tbat $ sometimes lay eggs in capti- 

 vity in tbe autumu, but it is uncertain if tbey would in a wild State. There is 

 probably a long ränge in tbe times of oviposition and batcbing. 



H. Scott (Cambridge). 



882) Shelford, K., Mimicry amongst tbe Blattidae; with a Revision 

 of the Genus Prosoplecta Sauss., and the Description of a new Genus. 

 In: Proc. Zool. Soc. London, Teil 2, S. 358—376, Taf. 48 (coloriert), 19V2. 

 The Blattidae in general are defenceless insects preyed on by many enemies, 

 from which they endeavour to escape by their cryptic habits and rapid movements. 

 The majority are obscurely coloured, harmonising with their inanimate surroun- 

 dings. But there are exceptions to this obscurely coloured type. (I) The author 

 deals first with certain Blattidae which have all the features associated with ex- 

 treme unpalatability : these are Polysosteria and certain allied genera of the Blat- 

 tinae, and their headquarters is Australia. Nearly all of them are apterous and 

 expose themselves freely, and all appear to be conspicuous, some being very 

 gaudily coloured, and many possess the pow^er of emitting an extremely repul- 

 sive odour. Certain species possess the habit of sunning themselves on the tops 

 of tree-stumps, etc. Cosmozosteria lateralis Walk, is brown with yellow markings 

 on thorax and abdomen: the 9*^ abdominal tergite bears two brilliant orange 

 Spots, which are concealed, when the insect is at rest, by this tergite being re- 

 tracted under the 8*^: but on the approach of an eneray the abdomen is disten- 

 ded and the brilliant orange spots conspicuously displayed. This species emits 

 an extremely vile smell. In America this group is represented by Enrycotis Stäl 

 and Pelmatosilpha Dohrn, many of which emit foul-smelling fluids: these insects 

 how^ever are not so conspicuously coloured as their Australian allies, and some of 

 them have cryptic habits. The nauseous Australian species are not mimicked by 

 other Orders of Insects or by other Blattidae, but it must be remembered that 

 Orthoptera in general do not serve as modeis to other Orders. 



(II) Several Blattidae mimic insects of other Orders, though usually in a 

 very generaHsed manner. There is no reason to consider these Blattidae unpala- 

 table. For example, the West African Eustegasta bupresfoiäes Walk., is metalHc 

 green with round yellow spots on the tegmina, and is very like a Buprestid 

 beetle: but the resemblance is only generalised, since no definite species of Bu- 

 prestidae is known which can be actually matched with the cockroach, and it is 

 unlikely that it w^ould be still undiscovered if it existed. Certain Central American 

 cockroaches resemble Lampyridae of the same region, not being definitely like 

 individual species, but having a generalised resemblance; these cockroaches do 

 not hide, but rest during the day exposed on leaves like the Lampyrids which 

 they resemble. Other examples are given of cockroaches bearing a generalised 

 resemblance to certain groups of Coleoptera and Hemiptera. At Hongkong 

 some little black Pentatomidae were found under a stone, and in Company with 

 them a similarly shaped and coloured cockroach: this the author regards as a 

 case, not so much of mimicry, as of "syncryptism" or "homoplasy". The female 

 cockroaches of the genera Perisphaeria and Pscudoglomeris roll themselves up into 

 balls when alarmed, and in form and colour closely resemble the pill-millipedes : 

 here again, no particular species of millipede appears to be copied, but the re- 

 semblance is a general one, which the author attributes to homoplasy. 



