CAMBRIDGE UNIVERSITY PRESS London: FETTER LANE, E.C. C. F. CLAY, Manager Edinburgh: 100, PRINCES STREET London: H. K. LEWIS, 136, GOWER STREET, W.C. WILLIAM WESLEY & SON, 28, ESSEX STREET, STRAND Berlin: A. ASHER AND CO. Leipzig: F. A. BROCKHAUS New York: G. P. PUTNAM'S SONS Bombay and Calcutta: MACMILLAN AND CO., Ltd . Frontispiece . Transformation of a Gnat ( Culex ). Magnified 5 times. Cambridge: PRINTED BY JOHN CLAY, M.A. AT THE UNIVERSITY PRESS With the exception of the coat of arms

The object of this little book is to afford an outline sketch of the facts and meaning of insect-transformations. Considerations of space forbid anything like an exhaustive treatment of so vast a subject, and some aspects of the question, the physiological for example, are almost neglected. Other books already published in this series, such as Dr Gordon Hewitt's House-flies and Mr O H. Latter's Bees and Wasps , may be consulted with advantage for details of special insect life-stories. Recent re

Among the manifold operations of living creatures few have more strongly impressed the casual observer or more deeply interested the thoughtful student than the transformations of insects. The schoolboy watches the tiny green caterpillars hatched from eggs laid on a cabbage leaf by the common white butterfly, or maybe rears successfully a batch of silkworms through the changes and chances of their lives, while the naturalist questions yet again the 'how' and 'why' of these common though wondrous

The caterpillar differs markedly from the butterfly. As we pursue our studies of insect growth and transformation we shall find that in some cases the difference between young and adult is much greater—as for example between the maggot and the house-fly, in others far less—as between the young and full-grown grasshopper or plant-bug. It is evidently wise to begin a general survey of the subject with some of those simpler cases in which the differences between the young and adult insect are compa

We may now turn our attention to some examples of the remarkable alternation of winged and wingless generations in the yearly life-cycle of the same species, mentioned at the end of the last chapter. Cockroaches and grasshoppers belong to an order of insects, the Orthoptera [5] , characterised by firm forewings and biting jaws; in all of them the change of form during the life-history is comparatively slight. A great contrast to those insects in the structure of the mouth-parts is presented by t

Insects as a whole are preeminently creatures of the land and the air. This is shown not only by the possession of wings by a vast majority of the class, but by the mode of breathing to which reference has already been made ( p. 2 ), a system of branching air-tubes carrying atmospheric air with its combustion-supporting oxygen to all the insect's tissues. The air gains access to these tubes through a number of paired air-holes or spiracles, arranged segmentally in series. It is of great interest

We are now in a position to study in some detail the transformation of those insects whose life-story corresponds more or less closely with that of the butterfly, sketched in the opening pages of this little book. In the case of some of the insects reviewed in the last three chapters, the may-flies and cicads for example, a marked difference between the larva and the imago has been noticed; in others, as the coccids, we find a resting instar before the winged condition is assumed, suggesting the

Among the insects that undergo a complete transformation, there is, as we have seen in the preceding chapter, an amount of inward change, of dissolution and rebuilding of tissues, that varies in its completeness in members of different orders. It is now advisable to consider the various outward forms assumed by the larvae of these insects, or rather by a few examples chosen from a vast array of well-nigh 'infinite variety.' In comparing the transformations of endopterygote insects of different o

The pupal stage is characteristic of the life-story of those insects whose larvae have wing-rudiments in the form of inpushed imaginal discs, and in all these insects there is, as we have seen, considerable divergence in form between larva and imago. In the pupa the wings and other characteristically adult structures are, for the first time, visible outwardly; it is the instar which marks the great crisis in transformation. The pupa rests, as a rule, in a quiescent condition, and during the earl

A number of interesting questions are associated with the seasonal cycle of an insect's life-history. In a previous chapter ( IV . pp. 30 , 34 ) reference has been made to the contrast between the long aquatic life of the larval dragon-fly or may-fly, extending over several years, and the short aerial existence of the winged adult restricted in the case of the may-flies to a few hours. Here we see that the feeding activities of the insect are carried on during the larval stage only; the may-fly

In the previous chapter we recognised how the seasonal changes in various species of butterflies as observable in two or three generations, indicate changes in the history of the race as it might be traced through innumerable generations. The endless variety in the form and habits of insect-larvae and their adaptations to various modes of life, which have been briefly sketched in this little book, suggest vaster changes in the class of insects, as a whole, through the long periods of geological

These names, given by geologists to the various divisions of rocks, as indicated by the fossils entombed in them, are arranged in 'descending' order, the more recent formations above, the more ancient below, as newer deposits necessarily lie over older beds....

The following list of some books and papers, referred to in this little volume or of especial service to the author in its preparation, is needless to say very far from exhaustive. To save space, titles are often abbreviated. Most of the works in the general list (A) contain extensive lists of literature on insects and their transformations, these should be consulted by the serious student....

1909. C. Börner. Die Verwandlungen der Insekten. Sitzb. d. Gesellsch. naturforsch. Freunde, Berlin . 1869. F. Brauer. Betrachtung über die Verwandlung der Insekten. Verhandl. der K.K. zool.-bot. Gesellschaft in Wien . XIX. 1899. G. H. Carpenter. Insects, their Structure and Life. London. 1859. C. Darwin. The Origin of Species. London. 1909. P. Deegener. Die Metamorphose der Insekten. Leipzig. 1906. J. W. Folsom. Entomology. London. 1878. C. Gegenbaur. Grundriss der Vergleichende Anatomie. Leipzi

1881. H. Adler. Ueber den Generationswechsel den Eichen-Gallwespen. Zeitsch. f. wissensch. Zoologie . XXXV. 1896. —— and C. R. Straton. Alternating Generations. Oxford. 1902. J. Anglas. Nouvelles Observations sur les Métamorphoses Internes. Arch. d'Anat. Microscop. IV. 1911. E. E. Austen. Handbook of the Tsetse-Flies. London (Brit. Museum). 1909. F. Balfour-Browne. Life-History of Agrionid Dragonfly. Proc. Zool. Soc. Lond. 1893, &c. C. G. Barrett. Lepidoptera of the British Islands. Lond

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