( XXV ) 



landscape, that in others with smaller powers or unable to fly 

 the instinct is merely to ascend. The effect of both tendencies 

 is to reduce the area over which the sexes have to find each other. 

 A somewhat deferred maturity and the gradual collection of 

 scattered individuals into swarms is probably associated with 

 the instinct in many cases, facilitating still further the meeting 

 of the sexes and the pairing of individuals from remote areas. 

 It is obvious that the gathering SAvarm will be far more easily 

 seen than single insects by the scattered individuals around. 

 The swarming of beetles, etc., round tree-tops is probably to be 

 thus explained. Related to the same combination of instincts 

 preparatory to pairing is the driving off of the winged males 

 and females by the workers of ant communities in response to 

 some probably atmospheric stimulus which makes itself felt on 

 a single day over a vast area. In the case of Lasius niger at El 

 Escorial in July 1902, the President had observed the workers 

 driving off the males and females in separate waves, thus 

 rendering it more probable that each would mature in the 

 presence of the opposite sex from other formicaria rather 

 than from their own. 



In the discussion which followed on the tendency of insects 

 to seek high and exposed places. Dr. T. A. Chapman suggested 

 that whereas it is necessary that hibernation should be as 

 complete as possible, hill-tops and similar situations would be 

 affected as places where the cold would be continuous. Com- 

 mander Walker said he had climbed to the top of Croagh 

 Patrick, a very isolated mountain in County Mayo about 

 2500 feet high early in the year, and found a number of 

 Coleoptera there as well as Calocam2xi vekista hibernating. Mr. 

 CniTTY drew attention to a paper on beetles recently published 

 by the Director of the observatory on the summit of Ben Nevis, 

 who attributed the presence of insects there to storms of wind. 

 Mr. Champion said that in the case of Dorcadion sp. on Mon- 

 cayo in North Spain which he found running about there on 

 the tops, as they were wingless, this could not be the cause of 

 their presence, while he had found ladybirds under the snow. 

 Colonel Yerbury mentioned the case of the Warble Fly, which 

 will always fly up to elevated gi'ound to pair, so that the 

 plan recommended by Miss Ormerod and other economic 



PROCI. EXT. SOC. LOND., II. 1904. C 



