MIMICRY AMONGST THE BLATTID^E. 359 



genus and of Platyzosteria Br., are fond of sunning themselves 

 on the tops of posts and tree-stumps. Commander j. J. Walker 

 when collecting in Australia frequently encountered a species, 

 Cosmozosteria lateralis Walk., which emitted so vile a smell that 

 he always refrained from touching it. This species is russet- 

 brown in colour with some variable yellow markings on the 

 thoracic and abdominal tergites, and on each posterior angle of the 

 ninth abdominal tergite is a brilliant orange-red spot ; when the 

 insect is at rest these two spots are almost concealed, the ninth 

 tergite being somewhat retracted within the preceding one, but 

 on the approach of an enemy the apex of the abdomen is elevated 

 and slightly distended so that the orange spots become conspicu- 

 ously displayed to view. A better example of a warning signal 

 associated with highly distasteful properties could not be found. 

 Prof. Baldwin Spencer, writing in 'Nature ' of July 28, 1892, 

 p. 309, says : — " One morning, when Mr. Frank Connelly and 

 myself were digging for worms, we accidentally cut in two a 

 cockroach. From between the segments in its back it poured 

 forth a milky-white fluid, possessing an odour so execrable and 

 pungent that it drove us from the spot." It is unfortunate that 

 the species was not identified, but I expect that it was one of the 

 Polyzosteria group. 



Commander J. J. Walker says of Periplaneta fortipes AValk., a 

 synonym of Platyzosteria novce-zealandice Br., that it is " very 

 evil-smelling/' but that its smell " is quite mild in comparison 

 with several of the Australian species." (Entom. Monthly Mao-. 

 (2) xv. p. 70(1904).) 



Dr. G. B. Longstaff recently took this species in some numbers 

 in New Zealand, finding it, however, not in exposed situations, 

 1 tut under logs and the bark of dead trees. Quoting from his note- 

 book Dr. Longstaff tells me that one specimen had a " moderate 

 cockroach odour, evanescent," of another that it had " a strong 

 peculiar fetor." The discrepancy may possibly be accounted for 

 by sexual differences (see remarks later on Eurycotis -floridana 

 Walk.). 



All the Australasian species of the Polyzosteria section appear 

 to be conspicuous insects. Many of them are shining black, a, 

 colour which is noticeable enough in Nature when associated 

 with free exposure ; others are black edged with yellow, or with 

 red legs. The species of Anamesia Tepp., are chestnut-brown 

 banded or margined with yellow. Cosmozosteria zonata Walk., 

 is black, banded with yellow or orange. Many of the species of 

 Polyzosteria Burm. are bright with metallic colours, and Eu- 

 zosteria mitchelli Angas, with its bronzy dorsal surface, spotted 

 and barred with orange or yellow, its pale yellow ventral surface 

 and sky-blue tibia?, is the most gaudy cockroach yet discovered 

 In the New World the Polyzosteria section of the BlattinaB i« 

 represented by the genera Eurycotis Stal, and Pelmalosilpha 

 Dohrn. The species do not appear to be so blatantly conspicuous 

 as their Australian relatives, but it seems likely that most, if not 



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