INSECTICIDES. 413 



taining the egg-clusters. Xone hatched. February 3. Ten 

 egg-clusters were treated with hydrogen sulphide for one 

 hour. None hatched. April 12. Some broken egg-clus- 

 ters were treated, in an open bottle, for two hours, with 

 hydrogen sulphide. None of them hatched. 



Hydrochloric Acid Gas. — March 31. Some egg-clusters 

 were submitted for fifteen minutes to the action of hydro- 

 chloric acid gas, formed by adding sulphuric acid to salt. 

 This destroyed the eggs by drying them up. Several egg- 

 clusters were submitted to the action of hydrochloric acid 

 gas for thirty minutes. None hatched. 



" Infernal" Mixture. — February 17. A number of new 

 egg-clusters were treated with a gas made by adding fifty 

 per cent, of sulphuric acid to fifty per cent of turpentine. 

 They were left exposed to the action of the gas over night, 

 which destroyed them so that none hatched. February 19. 

 Five e2:o:-clusters were treated for two hours with this iras. 

 The eo'o-s were bleached a little, and none hatched. Febru- 

 ary 22. Five egg-clusters were subjected for five hours to 

 the action of the above-mentioned gas. The eggs were 

 stained red, and shrivelled so that none hatched. Feliruary 

 22. Five eo-jr-clusters were submitted for ten hours to the 

 action of this gas, which entirely destroyed the eggs. Eggs 

 exposed to the action of this gas on February 19, for a 

 period of thirty minutes, were uninjured, and hatched on 

 March 24. 



Nitrogen Dioxide. — March 31. Several egg-clusters 

 were submitted to nitrogen dioxide for fifteen minutes. The 

 gas was formed by adding sulphuric acid to salt and nitre. 

 The eggs were entirely destroyed. April 1. A number of 

 egg-clusters were submitted for five minutes to the action 

 of nitrogen dioxide. The eggs were entirely destroyed. 

 August 24. Eo^o-s were treated with nitrous dioxide in a 

 hollow tree. The gas was generated as in the i)receding 

 experiments. After this treatment the eggs were taken into 

 a warm room, where they began to hatch on February 31. 



Potassic Cyanide. — March 15. A solution of potassic 

 cyanide in water, fifty per cent., and of alcohol, fifty per 

 cent., Avas dropped upon five egg-clusters, which it pene- 



