37 



on warm days, and that the eggs can survive the winter even if the 

 water in which they are laid should dry up temporarily. These 

 observations are remarkable in that A. maculipennis is not believed 

 to hibernate in the egg-stage. 



WiLLE (J.). Biologie und Bekampfung der deutschen Schabe {Phyllo- 

 dromia germanica, L.) [The Biology and Control of the German 

 Cockroach, Blatella germanica.] — Monographien ziir angeiv. Ento- 

 mologie, no. 5, Beiheft no. 1 to Zeitschr. angeic. Ent., Berlin, vii, 

 1920, 140 pp., 53 figs., 2 plates. [Received 6th December 1921.] 



This monograph deals minutely with the breeding, classification, 

 morphology and life-history of Blatella {Phyllodromia) germanica, L. 

 The influence of external stimuli on this species and the technique 

 employed in investigation are also described in detail. The remedial 

 measures described are applicable not only to this cockroach, but also 

 to Blatta (Periplaneta) orientalis, and Periplaneta americana. These 

 species devour a greater quantity and %'ariety of food and are chiefly- 

 responsible for injury on a large scale in warehouses. 



B. germanica is now a cosmopolitan species, chiefly found indoors, 

 but also occurring in forests. Its original home appears to be the old 

 eastern centres of civiHsation. It sometimes migrates in numbers 

 and thus invades new buildings under cover of night. Owing to its 

 larger number of eggs and its shorter developmental period it tends 

 to displace other cockroaches. It is chiefly found in rooms with a 

 temperature of about 20° C. [68° F.] and some degree of moisture. 

 The period of greatest activity in winter occurs between 5 and 7.30 p.m. 

 It was found that a first-stage larva can pass through a crack ^ mm. 

 high and 1 mm. wide. 



Parthenogenesis does not occur. At a temperature of 22° C. 

 [72° F.] the female carries the egg-cases for about 24 days until the 

 larvae hatch. The larval period lasts 172 days on an average at this 

 temperature, but at higher ones it may be as short as 75 clays. 



Liquids present an insurmountable barrier to P. germanica, which 

 never voluntarily enters water. Complete submersion for 2^3| hours 

 causes death. Preventive measures are of little value against cock- 

 roaches. Poison-baits are unsatisfactory in so far as no food is known 

 that is irresistibly attractive. Borax, salicylic acid, a mixture of two 

 parts borax and one of salicylic acid, and sodium silicofluoride, are 

 often employed indoors. Arsenicals are more efficacious but little 

 used. A dose of two milligrammes of arsenic trioxide (white arsenic) 

 pi-oves fatal in two days ; a stronger one does not kill more quickly. 

 Fumigation with hydrocyanic acid gas is considered to be the most 

 effective measure and it will also destroy any bugs, fleas, etc., thatmaj^ 

 be present. B. germanica is very susceptible to this gas, though 

 B. orientalis and P. americana are slightly less so. A strength of 

 0-124 volume per cent, kills the adult and aU the larval stages in two 

 hours. In practice fumigation lasts more than two hours, and a 

 minimum dose of 1 volume per cent, is used. The egg-cases of 

 B. germanica are readily destroyed, but those of the other species, 

 which are not carried by the female, are more resistant, though 

 24 hours' exposure to 1 volume per cent, destroys them. Experiments 

 in biological control did not give satisfactory results. A parasite, 

 Brachygaster minnius, 01., was observed, but its efficiency is 

 doubtful. 



