58 MISCELLANEOUS RESULTS OF WORK OF BUREAU — IX. 



scorching should be diluted with water, approximately two-thirds. 

 Fumigation should be carried on at night in a moist atmosphere, and 

 the house should remain closed all night. 



Fumigation with hydrocyanic-acid gas. a — When fumigating with 

 hydrocyanic-acid gas great care should be taken, as this gas is fatal to all 

 animal life. The work must be conducted at night and the plants 

 should have dry foliage. In treating this insect, use from 0.01 to 0.05 

 grams of potassium cyanid per cubic foot for from 2 hours to all night, 

 the strength and length of exposure varying according to the tight- 

 ness of the house and the kind of plants being treated, as there is 

 considerable difference between various plants as to their resisting 

 power to this gas. 



Spraying with nicotine liquids. — Nicotine extracts diluted with 

 water, if carefully applied to plants, will kill large numbers of the 

 greenhouse thrips, but the great objection is that many are not hit by 

 the spray, and therefore the plants become infested again in a short 

 time. 



Spraying with kerosene emulsion. b — It is quite possible that kero- 

 sene emulsion spray will be effective against the greenhouse thrips 

 when used at the strength of 1 part of stock to 10 parts of water and 

 it costs considerably less and is more readily obtained than the nico- 

 tine preparations. It should be very carefully prepared and used 

 experimentally at first until the effect on the foliage of the different 

 plants is noted. Care should also be taken to prevent a quantity of 

 emulsion from collecting around the roots. 



Water spray. — Frequent treatment with a stiff spray of water from 

 a garden hose will tend to keep this insect down, but unless there are 

 only a few plants it would be better to use one of the other remedies. 



Any treatment for this insect should be repeated in from 7 to 10 

 days to destroy the young larvae that have hatched from the eggs. 

 This should be sufficient, but it may be best to give a third treatment 

 in another week or two. 



BIBLIOGRAPHY. 



1. Bouche, P. F.c— Schadliche Garten Insecten, p. 42, 1833. 



Original description of the species. 



2. Haliday, A. H.— Entomological Magazine, Vol. Ill, p. 443, 1836. 



Description of the female as Heliothrips adonidum. 



3. Burmeister, H. — Handbuch der Entomologie, Vol. II, p. 412, 1838. 



Description of adult female and habits of insect. 



a For complete directions for the use of hydrocyanic-acid gas, see Cirs. 37 and 57, 

 Bur. Ent., U. S. Dept. Agr. 



o For the method of making emulsions, see Farmers' Bulletin 127, pp. 22-23, or 

 Cir. 80, Bur. Ent., U. S. Dept. Agr. 



c Not seen bv author. 



