(“on 4 [Ix 
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 very 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 Poutton 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 Poutton exhibited 325 butterflies captured 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 year. The follow- 
ing statement sets forth the constitution of the two sets of 
butterflies :— 
