Marvels of the Universe 



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About three weeks after leaving the 

 egg the grub spins a cocoon in some 

 curled-up leaf — 



often on beech and other 

 trees on which the infesting 

 green fly are more thinly 

 distributed and more active 

 in habits than those we find 

 on the rose-bushes. 



In favourable circum- 

 stances the Lace-wing Fly 

 larva grows very rapidly, and, 

 after moulting twice, becomes 

 full-grown in three or four 

 weeks after leaving the egg. 

 It now seeks a retired spot in 

 which to complete its trans- 

 formation. In some crevice, 

 or in a withered and curled-up 

 leaf, it spins around itself a 

 white silken cocoon formed of 



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— and with inarvellous ' skill he continues 

 to spin until he is completely hemmed 



the secretion of glands de- 

 veloped for the purpose which open into the mouth. When complete, the cocoon is almost spherical, 

 though slightly longer than broad, and very much shorter than the full-grown larva ; the latter, 

 indeed, has to lie curled up within it, with its head tucked under its tail. So closely is it packed 

 away, that it is marvellous indeed how it can retain sufficient freedom of movement to complete 

 the cocoon ; for it must be remembered that the spinning is all done from the inside. In this state 

 it remains throughout the winter ; but early in the following spring it sheds its skin once more, 

 and the pupa is disclosed. During its long rest it has decreased somewhat in bulk, so that it is now 

 not quite so tightly packed and has room to indulge in more freedom of movement; even yet, 

 however, the pupa is considerably longer than the cocoon in which it is enclosed, and both head 

 and tail are curled forward over the breast. The long slender legs of the fly can now be made out, 

 all folded against the lower side of the body, and the rudiments of wings are folded down between 



the second and third pairs of 



legs. The long, thread-like 



antennte, or " feelers," are 



curled back behind the eyes, 



and thence down with the 



legs and wings to the lower 



surface. Unlike the pupa of 



a moth or butterfly, the limbs 



are not firmly soldered down 



to the body, and are not 



even lightly attached, as in 



the pupee of beetles or bees, 



but each limb remains dis- 

 tinct. At first the difference 



between the pupae of the 



Lace-wing Fly and that of a 



bee, for instance (see Part 



VII.), is not very marked, 



because, though each limb is 



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The cocoon is much smaller than thi 

 grub, who has to curl hin^self up in th< 

 manner here ahown. 



When ready, the insect makes a clean 

 cut nearly round the cocoon, lifts the lid 

 and leaves his case empty as shown here. 



