GARDEN PESTS IN NEW ZEALAND 



Outstanding features in a life-cycle involving metamorphosis are 

 that growth takes place onlM in the larval state, and that the insect 

 parades through life in different guises egg, larva, pupa, and adult- 

 each with its own peculiarity of habit and form, although the adult and 

 pupa resemble one another much more than do the adult and larva ; but 

 no matter how dissimilar the larva, pupa, and adult may outwardly 

 seem, structures common to them all may be traced throughout. Make, 

 for example, a comparative study of the larva, pupa, and moth of the 

 magpie moth; the head, thorax, and abdomen can be seen in each stage, 

 while counterparts of the larval antennae, eyes, mouth-parts and feet 

 persist in the moth, though more or less profoundly modified during 

 pupal transformation. Although there are no external signs of w r ings 

 in the larva,, these appendages are developing, nevertheless, in concealed 

 "pockets" within the larval thorax, and, at the time of pupal formation, 

 become extruded and lie ensheathed with the legs and antennae in the 

 pupal cuticle along the sides of the pupal body. Apart from these 

 changes, the larval mouth parts undergo a most profound metamor- 

 phosis; apparently, though there is no similarity between the long 

 "tongue" or proboscis of the moth and the jaws and accessory jaws of 

 the caterpillar, the proboscis, adapted for sipping the nectar of flowers, 

 is nothing but the accessory jaws of the leaf-chewing larva greatly 

 elongated ; with the exception of the palpsl of the accessory jaws, the 

 other larval mouth parts are either absent in the moth or reduced to 

 vestiges. 



In the case of insects that develop without a metamoTphosis, the 

 life-cycle is one of comparative simplicity. An example of such an 

 insect is the so-called "silverfish" (Lepisma s&ccJiarina), common in 

 dwellings, especially in damp places, dark and dusty corners, flour and 

 sugar bins, while not uncommonly it causes some considerable damage 

 by devouring the paste and glaze from wallpapers and the binding and 

 leaves of books. 



The silverfish (Fig. 4), wingless 1 throughout life, measures about 

 one-quarter of an inch long when full grown ; it is silver-white in 

 colour, due to a clothing of| glistening scales that rub off as a silky 

 powder when the insect is handled. It glides rapidly about, especially 

 after dark, and is one of the most primitive insects, there being minute 

 leg-like processes attached in pairs to the under side of the abdomen; 

 the normal thoracic legs are well developed. The body is wedge-shaped, 

 tapering to the posterior end, from which three tail-like appendages 

 project, while anteriorly a pair of long, delicate antenna? arises from 

 the head. 



All stages of the silverfish, from the minute, freshly-hatched indi- 

 viduals to fully-grown ones, may be found in the one place, the smaller 

 ones being immature developing stages. In the case of another species 

 allied to the 1 common silverfish, the female lays from six to ten eggs 

 at one time in sheltered crevices, and the young hatch forty-five to sixty 

 days later, when the temperature ranges from 65 degrees to 68 degrees 

 Fahrenheit. 



Unlike the moth larva, that of the silverfish throughout its growth 

 resembles the adult both in habit and form, the only marked differences 

 being that of size and the absence of the abdominal leg-like appendages. 

 During growth several moults take place, and at the final one the adult 



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