GENERATION OF INSECTS. 435 



Kirbyi), the larva, by one of those marvellous and seemingly 

 prescient instincts which give so much interest to entomological 

 inquiries, covers the close and thick web of fine and soft silk which 

 it has prepared for its pupal repose, with a stronger outer defence of 

 portions of twigs irregularly bound together by silken filaments ; 

 thus suspended to a branch of the tree, it deceives, and escapes the 

 attacks of, predatory insectivorous birds. Some spin a thread, let 

 themselves down from their birth-tree by their silken cord, and bury 

 themselves in the earth, there to undergo their pupal sleep, as in a 

 grave, and to rise, gloriously transformed and winged, as at a resur- 

 rection. The pupae whose cocoon remains partially open, as in 

 Saturnia and Phrygmiea are usually called " guarded," {piipcB custO' 

 diatce). 



All pupae which are placed in dark situations are colourless, or of a 

 yellowish white, and become darker when exposed to the light. The 

 pupse of most butterflies, which are suspended in open day, are of a 

 green or yellowish brown colour ; some are speckled with glittering 

 spots of golden hue, either natural, or produced by the attacks of 

 parasitic insects ; and such pupae have obtained the name of " chry- 

 salis " and " aurelia." 



The active pupae of Orthoptera and Hemiptera are called "nymphs." 

 These insects, which are also said to have semi-complete pupae, and 

 to undergo an imperfect metamorphosis, are subjected, as I trust I 

 have already proved, to the same law of repetition or analogy which 

 is expressed so conspicuously in insects to which alone a perfect 

 metamorphosis has usually been attributed; for, although moulting 

 be no metamorphosis, even when accompanied, as it usually is in 

 insects, with a certain change in the form of the body, yet the course 

 of the development of those insects which, after exclusion from the 

 egg, are subject only to ecdysis and growth of wings during an 

 active nymph-hood, manifests, prior to exclusion, the same analogies, 

 which Oken expresses in the following words : — " Every fly creeps 

 as a worm out of the Qg%\ then, by changing into the pupa, it 

 becomes a crab ; and lastly a perfect fly." * 



It is not, indeed, true that every flying insect creeps, as a worm, 

 out of the Q^^^ ; all the Orthoptera and Hemiptera are excluded 

 under the type of the crab, i.e., with perfectly developed jointed legs, 

 eyes, antennae, and maxillary organs. The metamorphoses which 

 the locust undergoes in its progress from the potential germ to the 

 actual winged and procreative imago are nevertheless as numerous 

 and extreme as those of the butterfly. The differences are relative, 



* CCLXVI. p. 577. 



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