165 



rendering remedial measures almost useless. Killing the larvae and 

 adults, plastering up holes likely to shelter them, and destroying the egg- 

 masses were all tried without appreciably diminishing the numbers 

 present the next day. Borax however proved of great utility, either 

 scattered about in corners or mixed with a thick syrup and spread on 

 pieces of tinplate and placed under cupboards or other places where 

 the cockroaches sheltered. 



WiLHiiMi (J). Das Panke-Lietzengrabengelande bei Berlin als 

 Kriebelmiickenschadgebiet und die Immunitatsfrage. [ Ihe Districts 

 aroinid the Panke and Lietzengraben near Berlin as a dangerous 

 Simuliid x\rea and the Question of Immunity.] — Deutsche ticrdztl. 

 Wochenschr., Hanover, xxix, no. 31, 30th July 1921, pp. 383-384. 



The area around the Panke and the Lietzen canal near Berlin is 

 fa^'ourable for studying the bionomics of Simuliids. An examination 

 on 7th March 1921 showed an abundance of larvae, but no pupae, 

 which corroborates previous negative findings as to pupal hibernation. 

 Furthermore, the larvae were found in channels where none had been 

 seen in the preceding summer, when the water was at a lower level. The 

 winter level must therefore be taken as the standard, and this all the 

 more so as the dangerous spring swarms come from eggs laid in autumn. 

 On 30th March mature pupae of SimnUum {Odagnia) ornatiim and a 

 few adults were found. The swarming period closed on 28th April. 

 On the 27th a bull died that had been put out to graze the previous 

 day, and the author believes this death to be caused by S. ornatum. A 

 toxicological examination of dried specimens of this Simuliid is being 

 made with a view to clearing up this point. As regards immunity, 

 this case affords another instance of an animal dying shortly after 

 being put out to pasture, whereas others that have been grazing for a 

 longer period survive. It is possible that in the case of early pasturing 

 in regions with a sea climate and with a transition climate, immunity 

 is conferred owing to the early and gradual emergence of the Simuliids, 

 and that the varying number of deaths in regions with a land climate 

 ma}^ be due to a more or less sudden emergence and to the varying 

 degree of imnmnity acquired. It is remarkable that draught cattle, 

 which spend the winter in the open or are put out early in the year, 

 remain almost unaffected, even in dangerous zones. Experiments in 

 immunisation are to be carried out in connection with the toxicological 

 work mentioned above. 



Reh (L.). Schweflige Saure, Blausaure, Zyklon. [Sulphurous Acid 

 Gas, Hydrocyanic Acid Gas, and Zyklon.] — Der Praktische 

 Desinfekior, Dresden, xiii, no. 5, May 1921, pp. 35-37. [Received 

 5th August 1921.] 



From a careful study of sulphurous acid gas, Zj-klon, and hydro- 

 cyanic acid gas the author states that the last-named is undoubtedly the 

 most poisonous. Under equal conditions one volume of it per cent, kills 

 most living creatures in one to two hours, whereas Zyklon requires two 

 volumes and six hours, and sulphurous acid H-2 volumes and 24 hours. 

 Its penetrative power is greater than that of either of the others, as it is 

 lighter than them and than air. It is also the least injurious to metals, 

 fabrics, etc. ; only living plants and moist or oily food-stuffs require 

 to be removed from its influence. It is, however, much less convenient 



