( Ix ) 



even at 5000 ft., that butterfly life is reduced to a minimum 

 from want of sunshine, not from want of moisture, and I am 

 told that during this season for weeks at a time the sun is 

 scarcely seen at all. The period of the year when bvitterflies 

 are most abundant is during the dry season, if it may be 

 so called where the country never dries up at all. During the 

 wet season it is so wet and cold that vei"y few insects are on 

 the wing, but during the months of December — February 

 there is plenty of sunshine and quite sufficient moisture 

 for all needs of insects. It is curious that the seasons at 

 which the wet and dry phases are found do not vary much 

 from those further south, where the seasons are so very 

 different." 



Professor Poulton observed that the facts were extremely 

 remarkable, and must be taken into account in the attempt to 

 interpret the nature of the change from the one form into the 

 other. By themselves they seemed to suggest temperature 

 and not degree of moisture as the controlling factor. The 

 facts were, however, equally in accordance with the hypothesis 

 that the changes are due to internal causes and merely more or 

 less parallel with the seasons without being caused by them, 

 so that local reversal of the wet or dry periods is unaccom- 

 panied by a corresponding reversal in the phases of the insect. 

 But the problem is too difficult and complex to be solved by 

 these observations alone, interesting and suggestive as they 

 are. 



Professor Poulton exhibited 325 butterflies captui-ed on one 

 day by Mr. C B, Roberts, between the eighth and tenth mile 

 from the Potaro River on the road to the gold-mines. The 

 road starts from the Potaro 30 miles above its confluence with 

 the Essequibo. The capture was effected February 23, 1904, 

 and may be compared with that of August 28, 1903, exhibited 

 to the Society on November 4 of the same yea)\ The follow- 

 ing statement sets forth the constitution of the two sets of 

 butterflies : — 



