47. Larva of another Bipinnaria, showing the commencement of the Starfish.—_g_, canal of the ciliated sac; _i_, rudiments of tentacles; _d_, ciliated band. 48. Larva of Moth (_Agrotis_). 49. Larva of Beetle (_Haltica_). 50. Larva of Saw-fly (_Cimbex_). 51. Larva of _Julus_. 52. _Agrotis suffusa_. 53. _Haltica_. 54. _Cimbex_. 55. _Julus_. 56. Tardigrade. 57. Larva of _Cecidomyia_. 58. _Lindia torulosa_. 59. _Prorhynchus stagnalis_. 60. Egg of Tardigrade. 61. Egg of Tardigrade, after the yolk has subdivided. 62. Egg of Tardigrade, in the next stage. 63. Egg of Tardigrade, more advanced. ON THE ORIGIN AND METAMORPHOSES OF INSECTS. CHAPTER I. _THE CLASSIFICATION OF INSECTS._ About forty years ago the civil and ecclesiastical authorities of St. Fernando in Chili arrested a certain M. Renous on a charge of witchcraft, because he kept some caterpillars which turned into butterflies.[1] This was no doubt an extreme case of ignorance; it is now almost universally known that the great majority of insects quit the egg in a state very different from that which they ultimately assume; and the general statement in works on entomology has been that the life of an insect may be divided into four periods. Thus, according to Kirby and Spence,[2] “The states through which insects pass are four: the _egg_, the _larva_, the _pupa_, and the _imago_.” Burmeister,[3] also, says that, excluding certain very rare anomalies, “we may observe four distinct periods of existence in every insect,—namely, those of the egg, the larva, the pupa, and the imago, or perfect insect.” In fact, however, the various groups of insects differ widely from one another in the metamorphoses they pass through: in some, as in the grasshoppers and crickets, the changes consist principally in a gradual increase of size, and in the acquisition of wings; while others, as for instance the common fly, acquire their full bulk in a form very different from that which they ultimately assume, and pass through a period of inaction in which not only is the whole form of the body altered, not only are legs and wings acquired, but even the internal organs themselves are almost entirely disintegrated and re-formed. It will be my object, after having briefly described these changes, to throw some light on the causes to which they are due, and on the indications they afford of the stages through which insects have been evolved.