208 INTELLIGENCE IN INSECTS 
furiously hurrying to and fro. But if the colony is weak, 
the same kick, which at other times calls forth an army, 
will have the contrary effect. The ants which just before 
were running about the surface disappear through the en- 
trances of the nest as if by magic, and deathlike quiet 
succeeds.” 
Wagner in his valuable studies on the behavior of bumble 
bees, has observed that the bees of well populated nests 
are much more pugnacious than those from nests containing 
few members. In regard to the household activities of 
bumble bees Wagner remarks that ‘Wenn eine Hummel 
allein mit der Ausbesserung des Nestes beschaftigt ist, so 
erscheint ihre Tatigkeit, obwohl wie stets geschaftig, doch 
wenig energisch und intensiv. Kaum hat sich jedoch der 
ersten Hummel eine zweite angeschlossen, so nimmt_ bei 
gleichen sonstigen Bedingungen die Energie der Arbeit zu 
und wachst bei jedem neu hinzutretenden Mitarbeiter mit 
voller Augenscheinlichkeit. Gans dieselbe Erscheinung habe 
ich auch bei Grabwespen beobachtet.” The “brooding” 
of the cells, gathering food, and various other activities 
increase in vigor with increase in numbers, so that the popula- 
tion of the large nests seems larger and that of the small 
nests smaller than it is in reality. 
‘The influence of numbers upon the industry and courage 
of social insects has been adduced as a proof of a high degree 
of intelligence. That a populous ant colony will make an 
attack upon a neighboring nest, while a colony with few 
members shows a disinclination for warfare, may give the 
appearance of a conscious realization of strength and a 
power of reflecting upon the probable issue of an encounter. 
As Wagner has pointed out, the explanation of such pheno- 
mena may lie in the effect upon the individual of various 
stimuli caused by its associates. The ant or bee commonly 
