308 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



Lopus sulcatm {grisette de la vvjne). — Pratigeon destroys the adult 

 larvae by emulsions of petroleum spirit, or of carbon disulphide. So 

 as not to hurt the vine, he begins the treatment at the time when this 

 insect has ah-eady invaded the young grapes ; but it must be attacked 

 before hatching on the plants on which it feeds most willingly. A 

 slight shake is given to the stock ; the larvte, which are ah-eady clinging 

 to the vine, fall to the ground forthwith and the emulsion is then pro- 

 jected on to the soil. To kill the perfect insect, an emulsion diluted to 

 at least 2 per cent is projected on the fruit. 



112. Vaseline. — Action on Plants. — Vaseline is not harmless 

 to plants as might be imagined. It acts injuriously like petroleum 

 hydrocarbides. Shearer found that plants do not support with im- 

 punity larger doses than 10 per cent. Goethe and Marchal found 

 that vaseline used as an asphyxiating ointment on the cankers pro- 

 duced by the woolly aphis is injurious to the plant. 



Action on Insects. — Like oils and fats in general, vaseline acts 

 on insects as an asphyxiant ; it would appear at the same time to 

 exercise a toxic action analogous to that of petroleum on insects and 

 their larvae ; contact with it or its emulsions diluted even to 10 per cent 

 is deadly. 



Use. — Vaseline has been used to prepare the sulphuretted vaseline 

 invented by Meunier in 1887, to overcome the phylloxera. Vaseline 

 rapidly diminishes the evaporation of carbon disulphide in the soil, and 

 prolongs its action. Vaseline forms emulsions with soapy water of 

 the same strength as petroleum, and such emulsions are used in the 

 same condition ; they are especially used in England. Ward advises 

 an emulsion of vaseline 0-5 per cent, soap 1-25 per cent, against all 

 garden insects. 



Anthomyia Betce (beet fly) ; Antliomyia antiqua, Meig. (onion fly) ; 

 Antliomyia furcata, Bche. (onion fly) ; Anthomyia ceparum (onion 

 fly) ; Psila BoscB, Fabre (carrot fly). — Whitehead destroys these flies 

 by an emulsion of vaseline 10 per cent, soft soap 0-25 per cent. It is 

 used as a spray round the plant before the appearance of the fly. 



Thrips cerealium (ihrips of cereals). — Shearer destroys these insects 

 by spraying with emulsions of vaseline 7 per cent, soft soap 8 per cent. 



Aphides. — Plant lice are killed by an emulsion of vaseline O'75-l'O 

 per cent and soft soap 0-5-0-75 per cent (Whitehead) ; vaseline 

 3*5 per cent and soft soap 7 per cent (Shearer). 



Coccides. — To kill cochineals and kermes emulsions of vaseline 

 10-12 per cent, soft soap 8-10 per cent, must be used. 



113. Acetylene,^ C._,H.,. — Preparation. — Coal gas destroyed by 

 sparking oi- incompletely burnt yields this unsaturated hydrocarbide. 

 It is obtained commercially by decomposing with water acetylenic 

 carbides, such as calcium carbide. 



CaC, + 2R.fi = Ca(OH)., + aH,. 



As the commercial carbide is always impure, there is formed in ad- 



1 Acetylene is like coal-gas explosive when mixed with a certain amount of air. 

 Anyone storing calcium carbide must comply with the Home Office regulations 

 thereanent. — Tu. 



