THe HyMENOopPTERA OF MINNESOTA 199 
More than 2,000 species have been described, and it is estimated 
that there are probably 5,000 species in existence. Distinctively social 
insects for the most part, each colony is characterized by the presence 
of one or more queens, living in harmony (in this respect differing from 
social bees). There are also in each colony, worker ants which may 
be represented by more than one class, and in some species we find 
soldiers whose duty it is to fight for the colony they represent. The 
workers are sterile or undeveloped females. The soldiers are workers 
with large heads and powerful jaws. Their functions are those of 
Fig. 86. Formica fusca L., female. 
guarding the nest, fighting, crushing seeds, etc. Both male and 
female ants in most species are winged at time of mating, and it is 
no unusual thing in summer to see swarms filling the air during their 
nuptial flight. After this is accomplished, the females strip off their 
wings and proceed to egg-laying. There are, however, certain species 
in which wings are never developed. Where one or both of the sexes 
are wingless, mating must take place on or in the ground. The eggs 
of ants are white or yellowish and hatch in about fifteen days, tho 
at least one observer (Lubbock) claims a longer time is required, from 
30 days to six weeks. The pupal stage lasts from three to four weeks. 
The pupae are carried about by the workers to different places in the 
nest as occasion may require, and if one disturbs an ant nest in sum- 
