Essays upon heredity and kindred biological problems / by August Weismann ; authorized translation edited by Edward B. Poulton, Selmar Schönland and Arthur E. Shipley.

  • August Weismann
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Essays upon heredity and kindred biological problems / by August Weismann ; authorized translation edited by Edward B. Poulton, Selmar Schönland and Arthur E. Shipley. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    to use their large wings for flight, because the body is too heavily- weighted by a mass of eggs, all of which reach maturity at the same time. Such species, as for instance Aglia tau, are unable to dis- tribute their eggs over a wide area, but are obliged to lay them all in a single spot. They can however do this without harm to the species, because their caterpillars live upon forest trees, which pro- vide abundant food for a larger number of larvae than can be pro- duced by the eggs of a single female. The eggs of Aglia taio are deposited directly after pairing, and shortly afterwards the insect dies at the foot of the tree among the moss-covered roots of which it has passed the winter in the pupal state. The female moth seldom lives for more than three or four days; but the males which fly swiftly in the forests, seeking for the less abundant females, live for a much longer period, certainly from eight to fourteen days ^. The females of the Psi/cJddae also deposit all their eggs in one place. The grasses and lichens upon which their caterpillars live grow close at hand upon the. surface of the earth and stones, and hence the female moth does not leave the ground, and generally does not even quit the pupa-case, within which it lays its eggs ; as soon as this duty is finished, it dies. In relation to these habits the wings and mouth of the female are rudimentary, while the male possesses perfectly developed wings. The causes which have regulated the length of life in these cases are obvious enough, yet still more striking illustrations are to be found among insects which live in colonies. The duration of life varies with the sex in bees, wasps, ants, and Termites : the females have a long life, the males a short one ; and there can be no doubt that the explanation of this fact is to be found in adaptation to external conditions of life. The queen-bee—the only perfect female in the hive—lives two to three years, and often as long as five years, while the male bees or drones only live four to five months. Sir John Lubbock has succeeded in keeping female and working ants alive for seven years—a great age for insects ^,—while the males only lived a few weeks. ^ This estimate is«derived from observation of the time during which these insects are to be seen upon the wing. Direct observations upon the duration of life in this species are unknown to me. Sir John Lubbock has now kept a queen ant alive for nearly 15 years. See note 2 on p, 51.—E. B. P.]