282 



Chemotropic Resjyonses of Insects 



disposal the short period of only 10 weeks wherein to conduct these ex- 

 periments, they can only be regarded as essentially preliminary in nature. 

 War conditions also added to the difficulty in procuring certain reagents, 

 and the summer of 1918 proved to be one of the wettest for a number of 

 years. During the months of July-September there was scarcely more 

 than two clear sunny weeks. Our observations were conducted at Lymm 

 (Cheshire) in an orchard and vegetable garden, and the immediate 

 surroundings are indicated in Fig. A. Less than 60 yards away are farm 

 buildings and accompanying manure heaps which provide sustenance 

 for great numbers of Diptera. 



The length of exposure of a substance was generally 24-48 hours, 

 but sometimes longer or shorter according to circumstances. Mr Husain, 

 however, has not given very exact data upon this point. In all cases in 

 which long exposures were resorted to, it was owing to adverse weather 

 conditions which necessitated more lengthy trials. 



As our observations are the first of their kind conducted in this 

 country, we have deemed it advisable to publish them as they stand, 

 without drawing any definite conclusions therefrom. We have laid 

 particular stress upon the difficulties of the work, with a view of warning 

 other intending observers of the pit-falls they are likely to encounter. 



IV. Observations conducted at Lymm (Cheshire) 

 DURING July and August, 1918. 



(1) The following substances gave negative results, i.e. no insects 

 were attracted, and it is probable that some of the agents used are 

 powerful repellents. 



Oil of cajeput 

 orange 

 lemon 



sandal wood { Exposed on two occasions, 

 bergamot 

 cloves 

 juniper 

 Birch tar oil 

 Oil of aniseed 



„ citronella 

 Menthol 

 Turpeniol 

 /Potassium hydroxide (5'J{j) 

 1 Hydrochloric acid (5%) 

 -'^ iSulph uric acid (5%) 



Malic acid (5%) 



VBcnzaldehyde (5%) 





Exposed on three occasions. 

 Exposed on six occasions. 



► Exposed on two occasions. 





