86 THE CANADIAN ENTOMOLOGIST. 



made them susceptible to chemotropic stimuli from a food view- 

 point. 



At a temperature of 70° F, about one-half were active and 

 at 75° F. all were active. When the temperature was suddenly 

 lowered as from 75° to 36° F. all became dormant at once and 

 exhibited no tropic reactions, By at once I mean within ten or 

 twelve minutes. Without doubt thermotropism plays an import- 

 ant if not the most important part in deciding just what reactions 

 are to occur. A gradual lowering of the temperature such as 

 would naturally result in the beetles acting phototropically and 

 thigmotropically while a sudden drop resulted in what might be 

 called immediate partial hibernation. Of course with a soft 

 bodied insect this would have resulted in death. When the 

 temperature of the air was 42° F., that of their natural hiber- 

 nation place was 54° F. which indicates an effort to secure opti- 

 mum conditions. 



After emerging from winter quarters, the females of Cidexr 

 pipiens are at first positively chemotrophic. After having fed: 

 they become positively hydrotropic and deposit their eggs on 

 the surface of water. While in hibernation during which time 

 they may be fairly active, depending on the temperature of their 

 hibernation quarters, they are strongly negatively hydrotropic. 

 Food and water placed within easy reach of hibernating speci- 

 mens were always avoided, even when the temperature of their 

 surroundings was 75° or 80° F. 



Aedes soUicitans and Aedes cantator are also positively 

 hydrotropic but not to the extent of most other mosquitoes. 

 With these species eggs are deposited in damp depressions and 

 not on the surface of the water. Sterile females of both of these 

 species are strongly negatively hydrotropic and fly long distances 

 away from salt marshes where they breed. However this migra- 

 tory habit, or at least the direction they take, is undoubtedly 

 influenced by anemotropism inasmuch as they allow themselves 

 to be carried by strong breezes and will fly inward against light 

 breezes. Sterile females of Aedes tceniorhynchus, which has a 

 similar life history to soUicitans are to a certain extent negatively 

 hydrotropic. 



