GARDEN PESTS IN NEW ZEALAND 



from a worm. The larva has a distinct head, a pair of eyes, and short 

 antenna^ and a set of mouth parts, similar to those of the weta; or 

 grasshopper, well adapted for devouring foliage; the first three segments 

 behind the head correspond to the thorax of the moth, and each bears 

 a pair of short feet; the remaining segments are those of the abdomen, 

 andi 'have no true feet, but six pairs of sucker-like appendages called 

 pro-legs. The number of pro4egs varies from four to six pairs, accord- 

 ing to the species of moth, and are found only on the larva. 



The time occupied by larval development of the magpie moth 

 varies from forty to eighty days in summer and autumn ; but if winter 

 intervenes, causing the larvae to hibernate before completing their 

 development, the larval period may be as long as two hundred and forty- 

 eight days; normally this insect hibernates in the larval state, com- 

 pleting its development during the following spring. Throughout 

 winter the larvae hibernate singly or in colonies under loose bark, in leaf 

 axils, or any suitable crevice. 



The fully-grown larva measures about one and a-half inches long. 

 Prior to the final moult it ceases to feed, and wanders in search of a 

 suitable place in which to undergo the next transformation, usually 

 among stones, rubbish, or under loose bark, etc. There it spins a white 

 silken cocoon, among the strands of which are entangled the long black 

 body hairs; herein the larva undergoes the final moult, the cast cuticle 

 being easily seen at one end inside the cocoon. 



The insect, however, has now assumed a form quite diiferent from 

 that of the larva; this form is the chrysalis of^pupa, and as such is 

 incapable of locomotion and feeding. The pupa measures about three- 

 quarters of an inch long, is yellowish at first, but soon becomes black 

 with yellow markings, while the form of the future moth (head, 

 antennae, thorax, legs, wings and abdomen) can be traced oil the pupal 

 cuticle. After from about two to five weeks, the pupa opens by a cross- 

 shaped slit on the back just behind the head., and the moth draws itself 

 out. At first the moth is comparatively helpless after having been 

 confined within the limited space of the pupal cuticle ; soon, however, 

 the body hardens, the wingtj smooth out, and the insect is ready for 

 flight. 



Metamorphosis is carried to a much higher state of perfection in 

 the case of such insects as blowflies and houseflies (Fig. 4). The larva, 

 or maggot, is without any external sign of head and legs, though these, 

 together with the wings of the future fly, develop from rudiments 

 within the body of the maggot. At the final moult the larval cuticle 

 is not discarded, as in the case of the moth, 'but hardens to form a case 

 the puparium witnin which the pupa lies. 



The life-cycle of the magpie moth is illustrative of the . principles 

 of metamorphosis characterising the development of a great many 

 insects, such as all moths and butterflies, beetles, flies, bees and wasps, 

 etc.; but, although the general characters of the larva, pupa, and adult 

 moth are common, with but slight variation, to corresponding stages 

 of moths and butterflies as a whole, these stages in other insects, though 

 readily recognised, have their own characteristics. 



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