;82 



Marvels of the Universe 



The first transition which 

 taUes place in the cocoon, the 

 grub changing to chrysalis. 



Photos bu Ilngli ifaiu, ll.^'c, F.E.S. 



The mature chrysalis (un- 

 curled!, showing already the an- 

 tennae of the perfect insect. 



separate, they are, nevertheless, quite motionless for the very good 

 reason that the muscles to move them are not yet developed. But as 

 the fly within the delicate pupa shell approaches maturity, the muscles 

 are formed, and when almost ready for emergence the limbs of the 

 pupa become functional, 



In this stage, too, the insect is furnished with a pair of powerful jaws, 

 unlike those of the larva and unlike those of the fly — jaws, in fact, useful 

 only to the pupa, and that for one special purpose. The muscles that 

 work these, like the muscles that move the limbs, only become functional 

 late in pupal life ; but when the insect is ready to emerge, the first 

 operation is for the pupa bj? means of these jaws to make a clean cut 

 nearly round one end of the cocoon : it then crawls out of the cocoon, 

 forcing up the lid to do so ; as soon as it is clear, this falls back by the 

 natural elasticity of the part left as a hinge, so that at first sight the 

 empty cocoon still appears complete. The pupa now, but for its imper- 

 fecth^ developed wings, closely resembles the perfect fly, both in appear- 

 ance and colour. It endeavours to find some upright rough surface, such 

 as that afforded by a fence or tree-trunk, up which it can climb, in order 

 that its final transformation may be successful. After a short rest the 

 skin splits down the back, and through the rent the fly emerges. At first 

 the wings are quite small and shrivelled in appearance, but are soon 

 expanded by the forcible injection of blood into their veins ; even now 

 they are moist and limp, and are kept hanging vertically downwards 

 while they harden. If the insect has not been able to find a support that 

 enables it to assume this position, the wings are almost certain to be 

 crippled and useless for flight. When sufficiently stiff, they are turned 

 down roof-wise over the body, as seen on this page ; but some little 

 time has yet to elapse before they are ready for use. Early morning, and 

 again the late afternoon, appear to be the favourite times for the 

 emergence of the Lace-wing Fly, and about these hours the newly- 

 emerged flies are common objects upon walls and fences. 



COLOURED STARS 



BY G. F. CH.\MBERS, F.R..-V.S. 



With a few notorious exceptions the Stars which we see shining in the 

 heavens on an ordinary clear night are devoid of colour, e-xhibiting, as a 

 rule, a more or less pure white light. The exceptions to this rule are 

 single Stars of a yeUow or deep orange, or fiery red colour. These are 

 not uncommon, but isolated blue or green Stars are very rare. Indeed, 

 amongst the conspicuous Stars I can only recall one that is green, 

 namely, /3 Librse. The German astronomer Kruger has given the 

 following as typical coloured Stars : 



White. — Sirius (o Canis ilajoris) ; Altair (o Aquilas) ; Regulus (a 

 Leonis). 



YeUow. — CapeUa (o Aurigse) ; Pollux (/3 Geminorum) ; Arcturus (a 

 Bootis). 



Orange-red. — a Herculis : Betelgeuze (« Orionis). 



Colour in connection with Stars comes under our notice more directh' 



