Because only a few of them afford mutual assistance in their labours. The greater number follow their pursuits singly ; many, as spiders, live in society when young, but afterwards separate, and live in a state of solitude, seeing creatures of the same species only at the time of pairing. Swift very aptly observes, " suspense is the life of the spider."
The labours of such insects as live in communities are, however, very remarkable ; since they thus build common residences, by their united powers, and under the guidance of an extremely regular, geometrical, innate instinct. There are but few creatures of this class which do not, at least once in their life, give proofs of this natural power of construction; either as the cloth moth and water moth, form a habitation in their incomplete and larva state; or, like others, spin and prepare a receptacle to contain them during their metamorphosis and death-like sleep ; or, like the lion-ant, dig pits : or, like the spider, weave webs for their prey, and bags or nets for the security of their posterity, and in which they deposit their eggs.
All those insects which live in society, when exposed to cold, are observed to cluster together, as if to keep each other warm. Some, indeed, when exposed to cold, become torpid, and revive upon the restoration of a suitable temperature; but there are others, as the honey bee, which resist any reduction of their temperature below their ordinary digestive heat, and preserve it in their dwellings, even during the winter season. John Hunter found a hive in July 18, at 82°, when the temperature of the air was only 54° ; and in December 30, at 73°, when the air was only 35°. - (Phil. Trans.) When cooled, until they become become benumbed, they seldom recover, while the wasp, belonging to the same natural order, can be rendered torpid, and again revived with safety.
Because the analogies derived from the transformation of insects admit of some beautiful applications, which have not been neglected by pious entomologists. The three states of the caterpillar, larva, and butterfly, have, since the time of the Greek poets, been applied to typify the human being ; its terrestrial form, apparent death, and ultimate celestial destination: and it seems more extraordinary, that a sordid and crawling worm, should become a beautiful and active fly; that an inhabitant of the dark and fetid dunghill, should in an instant entirely change its form, rise into the blue air, and enjoy the sunbeams, - than that a being, whose pursuits here have been after an undying name, and whose purest happiness has been derived from the acquisition of intellectual power and finite knowledge, should rise hereafter into a state of being, where immortality is no longer a name, and ascend to the source of Unbounded Power and Infinite Wisdom. - Sir H. Davy - Salmonia.