On the Origin and Metamorphoses of Insects

CHAPTER I.. The Classification of Insects.

THE CLASSIFICATION OF INSECTS.

Introduction.--Stages in the Life of an Insect.--Classification of Insects.--Characters derived from the Wings; from the parts of the Mouth; from the Metamorphoses.--The Classes of Insects: Hymenoptera, Strepsiptera, Coleoptera, Euplexoptera, Orthoptera, Thysanoptera, Neuroptera, Trichoptera, Diptera, Aphaniptera, Heteroptera, Homoptera, Lepidoptera page 1-26

CHAPTER II.. The Influence of External Conditions on the Form and Structure

THE INFLUENCE OF EXTERNAL CONDITIONS ON THE FORM AND STRUCTURE OF LARVÆ.

Larvæ depend partly on the group to which they belong.--Wood-eating Larvæ.--Larvæ of Lamellicorns.--Larvæ depend also in part on mode of life.--Larvæ of Hymenoptera, of Sirex; of Tenthredo; of Ichneumons; of Bees.--Rudimentary legs of Bee Embryo.--Beetles, Weevils, Scolytus, Crioceris, Sitaris, Metamorphoses of Pteromalidæ. Platygaster, Polynema.--Influence of external conditions.--Developmental and adaptive Metamorphoses page 27-41

CHAPTER III.. The Nature of Metamorphoses.

THE NATURE OF METAMORPHOSES.

The life history of an Insect must be considered as a whole.--Vagueness of the term Larva.--Some larvæ much more advanced than others.--Organs develope in different order, in different groups.--Suppressed stages.--Apod condition of Phryganea; of Aphis; of Chrysopa.--Libellulidæ.--Donacia.--Spiders.--Myriapods.--Apod stage of Homomorphous Insects once probably longer than now.--Suppression of embryonic stages.--Metamorphoses of Hydroida, Crustacea, Isopods, and Amphipods.--Echinoderms.--Variations in development induced by the influence of external conditions. page 41-62

CHAPTER IV.. The Origin of Metamorphoses.

THE ORIGIN OF METAMORPHOSES.

Origin of Metamorphoses.--Views of Messrs. Kirby and Spence.--Nature of the question.--Young animals often more similar than mature.--Views of Darwin, Herbert Spencer, Johannes Müller, Fritz Müller, and Agassiz.--Effect of size of egg.--Insects leave the egg in a more or less developed condition.--Consideration of pupal condition.--Quiescence of pupa.--Period of quiescence at each moult.--Changes not so abrupt as generally supposed.--Change in mouth-parts.--Difficulty in reference to Darwinian theory.--Mouth-parts of Campodea and Collembola, as intermediate between the mandibulate and haustellate types.--Change in mouth-parts as connected with pupal conditions.--Origin of wings.--Use of wings under water.--Connection of metamorphoses with alternation of generations.--Parthenogenetic larvæ of Cecidomyia.--In alternation of generations one form always agamic.--Dimorphism and Dieidism.--Summary and Conclusions page 62-81

CHAPTER V.. The Origin of Insects.

THE ORIGIN OF INSECTS.

The Origin of Insects.--Mistaken views of Darwinian theory.--Natural selection a vera causa.--Application of Darwin's views to Insects.--Similarity of young Crustacea as compared with mature forms; ditto in Insects.--Type of Insecta.--Two principal types of larvæ: Hexapod and Apod.--Conclusions to be drawn from them.--Campodea the modern representative of the Insect-stock.--Campodea, perhaps derived from Tardigrade.--Vermiform or Apod type of larva.--Views of Fritz Müller, Brauer, and Packard.--Represents a still earlier ancestor.--Modern representatives.--Notommata, Albertia, Lindia.--Earlier forms difficult to trace.--Lowest forms of animal life.--Yolk-segmentation.--Embryology and Evolution.--Light thrown by the evolution of the individual on that of the species page 82-108

DESCRIPTION OF THE PLATES.

PLATE I. p. 7.

FIG.

1. Cricket. Westwood, Intro. to the Modern Classification of Insects, vol. i. p. 440.

2. Earwig. Westwood, loc. cit. vol. i. p. 399.

3. Aphis. Packard, Guide to the Study of Insects, pp. 521, 522.

4. Scolytus. Westwood, loc. cit. vol. i. p. 350.

5. Anthrax. Westwood, loc. cit. vol. ii. p. 538.

6. Balaninus.

7. Cynips. Westwood, loc. cit. vol. ii. p. 121.

8. Ant (Formica). Westwood, loc. cit. vol. ii. p. 218.

9. Wasp. Ormerod, Nat. Hist. of Wasps, pl. i. fig. 1.

PLATE II. p. 8.

FIG.

1. Larva of Cricket. Westwood, loc. cit. vol. i. p. 440.

2. Larva of Aphis. Packard, loc. cit. pp. 521, 522.

3. Larva of Earwig. Westwood, loc. cit. vol. i. p. 399.

4. Larva of Scolytus. Westwood, loc. cit. vol. i. p. 350.

5. Larva of Anthrax. Westwood, loc. cit. vol. ii. p. 546.

6. Larva of Balaninus.

7. Larva of Cynips. Westwood, loc. cit. vol. ii. p. 121.

8. Larva of Ant (Formica). Westwood, loc. cit. vol. ii. p. 226.

9. Larva of Wasp. Newport, Art. Insecta, Todd's Cycl. Anat. and Phys., p. 871.

PLATE III. p. 14.

FIG.

1. Chloëon. Linn. Trans. 1866.

2. Meloë. Spry and Shuckard, Coleoptera Delineated, pl. 56.

3. Calepteryx.

4. Sitaris. Spry and Shuckard, loc. cit. pl. 56.

5. Campodea. Suites à Buffon. Aptéres.

6. Acilius. Westwood, loc. cit. vol. i. p. 100.

7. Termes. Westwood, loc. cit. vol. ii. p. 12.

8. Stylops. Duncan, Met. of Insects, p. 387; Packard, p. 482.

9. Thrips. Westwood, loc. cit. vol. ii. p. 1.

PLATE IV. p. 15.

FIG.

1. Larva of Chloëon. Linn. Trans. 1863.

2. Larva of Meloë. Chapuis and Candèze, Mem. Soc. Roy. Liége, 1853, pp. 1, 7.

3. Larva of Calepteryx. Dufour, Ann. Sci. Nat. 1852.

4. Larva of Sitaris. Duncan, Met. of Insects, p. 309.

5. Larva of Campodea. Gervais' Suites à Buffon. Aptéres.

6. Larva of Acilius. Westwood, loc. cit. vol. i. p. 100.

7. Larva of Termes. Duncan, loc. cit. p. 348.

8. Larva of Stylops. Westwood, Trans. Ent. Soc. 1839, vol. ii. pl. xv. fig. 13a.

9. Larva of Thrips. Westwood, loc. cit. vol. ii. p. i.

PLATE V. p. 99.

FIG.

1-5. Protamoeba.

6-9. Protamyxa aurantiaca. Haeckel Beit. zur. Monog. der Moneren, pl. 1.

10-18. Magosphoera planula. Haeckel, loc. cit. pl. v.

PLATE VI. p. 105.

FIG.

1-4. Yolk-segmentation in Laomedea. After Allman. Mon. of Tubularian Hydroids. Ray Society.

5-9. Yolk-segmentation in Filaria. After Van Beneden. Mem. sur les Vers Intestinaux.

10-13. Yolk-segmentation in Echinus. After Derbès. Ann. des. Sci. Nat. 1847.

14-17. Yolk-segmentation in Lacinularia. After Huxley. J. of Mic. Sci. 1853.

18-21. Yolk-segmentation in Purpura. After Koren and Danielssen. Ann. des. Sci. Nat. 1853.

22-24. Yolk-segmentation in Amphioxus. After Haeckel. Naturliche Schöpfungsgeschichte, pl. x.

25-29. Yolk-segmentation in Vertebrate. After Allen Thompson. Art. Ovum. Cyclop. of Anatomy and Physiology.

DESCRIPTION OF THE FIGURES.

FIG. 1. Larva of the Cockchafer (Melolontha)

2. Larva of Cetonia.

3. Larva of Trox.

4. Larva of Oryctes.

5. Larva of Aphodius.

6. Larva of Lucanus.

7. Larva of Brachytarsus.

8. Larva of Crioceris.

9. Larva of Sitaris humeralis.

10. Larva of Sitaris humeralis, in the second stage.

11. Larva of Sitaris humeralis, in the third stage.

12. Larva of Sitaris humeralis, in the fourth stage.

13. Pupa of Sitaris.

14. Larva of Sirex.

15. Egg of Rhynchites, showing the parasitic larva.

16. The parasitic larva, more magnified.

17. Egg of Platygaster.

18. Egg of Platygaster, showing the central cell.

19. Egg of Platygaster, after the division of the central cell.

20. Egg of Platygaster, more advanced.

21. Egg of Platygaster, more advanced.

22. Egg of Platygaster, showing the rudiment of the embryo.

23. Larva of Platygaster.--mo, mouth; a, antenna; kf, hooked feet; r, toothed process; lfg, lateral process; f, branches of the tail.

24. Larva of another species of Platygaster. (The letters indicate the same parts as in the preceding figure.)

25. Larva of a third species of Platygaster. (The letters indicate the same parts as in the preceding figure.)

26. Larva of Platygaster in the second stage.--mo, mouth; slkf, oesophagus; gsae, supra-oesophagal ganglion; lm, muscles; bsm, nervous system; gagh, rudiments of the reproductive glands.

27. Larva of Platygaster in the third stage.--mo, mouth; ma, mandibles; gsae, supra-oesophagal ganglion; slk, oesophagus; ag, ducts of the salivary glands; bnm, ventral nervous system; sp, salivary glands; msl, stomach; im, imaginal discs; tr, tracheæ; fk, fatty tissue; ed, intestine; ga, rudiments of reproductive organs; ew, wider portion of intestine; ao, posterior opening.

28. Embryo of Polynema.

29. Larva of Polynema.--asch, rudiments of the antennæ; flsch, of the wings; bsch, of the legs; vfg, lateral projections; gsch, rudiments of the ovipositor; fk, fatty tissue.

30. Egg of Phryganea (Mystacides).--A^1, mandibular segment; C^1-C^5, maxillary, labial, and three thoracic segments; D, abdomen.

31. Egg of Phryganea somewhat more advanced.--b, mandibles; c, maxillæ; cfs, rudiments of the three pairs of legs.

32. Egg of Pholcus opilionides, showing the Protozonites.

33. Embryo of Julus.

34. Colony of Bougainvillea fruticosa, natural size, attached to the underside of a piece of floating timber.

35. Portion of the same, more magnified.

36. The Medusa from the same species.

37. Larva of Prawn, Nauplius stage.

38. Larva of Prawn, more advanced, Zoëa stage.

39. Larva of Echino-cidaris oequituberculata seen from above ×6/10.

40. Larva of Echinus × 100.--A, front arm; F, arms of the mouth-process; B, posterior side arm; E^1, accessory arm of the mouth-process; a, mouth; a^1, oesophagus; b, stomach; b^1, intestine; o, posterior orifice; d, ciliated bands; f, ciliated epaulets; c, disc of future Echinus.

41. Comatula rosacea.

42. Larva of Comatula rosacea.

43. Larva of Comatula rosacea, more advanced.

44. Larva of Comatula rosacea, in the Pentacrinus state.

45. Larva of Starfish (Bipinnaria), × 100.

46. Larva of Starfish (Bipinnaria), × 100, seen from the side.--a, mouth; b, oesophagus; c, stomach; c^1, intestine.

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._

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. 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.

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