1618. The duration of the lives of insects is extremely variable. The majority, in all probability, are annual; emerging from the egg, and passing through their metamorphoses within the year. Yet there are many facts to prove that certain families (particularly among the beetles) are long-lived. The late Mr. Marsham detected a foreign coleopterous insect in a piece of wood, which formed a desk that had been in a public office for nearly twenty years: in which case, the larva must have been imported in the wood, and, not being disturbed by the joiner, must have remained the greater part of this time in the larva and pupa states before it ate its way out as a perfect beetle. The greater proportion of moths pass the winter underground in the chrysalis state. Butterflies are mostly annual; although some few survive the winter, and appear early in the spring: in many species, both of butterflies and moths, there are, however, two broods in a year. The transitory life of the Ephemera, or day-fly, is proverbial; the perfect insect, indeed, of some species exists but for a few hours, and seems born only to provide for the continuation of its species; yet in the larva state it enjoys an aquatic life of two or three years. Bees are known to live for two or three years; and the same may be said of those spiders which take up their residence in cellars and other dark abodes.
