8o 



Marvels of the Universe 



will fly in and probably alight on the table, after flying around the light, and can then be examined 

 at leisure. 



Though the light has its highest development in the mature female, it is present in the insect at 

 all stages of existence. The small spherical eggs are luminous from .the moment they are deposited, 

 in the second half of July, until they hatch some four or five weeks later. The grub, too, is luminous, 

 and the same may be said of the chrysahs. 



The Glow-worm is a life-long enemy to snails and slugs ; in fact, these molluscs constitute the 

 sole food of this insect. It would appear to be a somewhat difficult matter for a Glow-worm to 



attack so sensitive a creature as the snail, 

 who quickly withdraws his very soft body 

 well into his shell at the slightest alarm. 

 But from the moment he is well out of the 

 egg-shell the grub seeks for the nearest 

 snail and opens the attack, though he may 

 have to crawl half into the shell in pursuit, 

 j ^^p ' He thus gets the snail into a corner from 



which there is no retreat, and he eats 

 steadily on until the snail-shell is quite 

 empty. That is the explanation of the 

 majority of empty and unbroken snail- 

 shells you may find under almost any 

 hedge. The others probably have become 

 vacant through the death of the snail 

 from old age — if ever so-persecuted a 

 creature does die a non-violent death. 



How is the Glow-worm's light pro- 

 duced ? and what is its purpose ? These 

 questions have not yet been answered 

 with entire satisfaction. Several explana- 

 tions have been put forward. It was 

 formerly the custom to speak of all lumino- 

 sity produced by animals and plants as 

 " phosphorescence." That term has been 

 dropped because to most people it im- 

 plied that the light was due to phosphorus. 

 But what is the exact nature of the lumi- 

 nosity has yet to be determined. Its pur- 

 pose has been stated to be to enable the 

 winged male to find the wingless female ; 

 but though this is probably one reason there must be others, or else the eggs and the grub would 

 scarcely be provided with the same light. Moreover, scent appears to play a more important 

 part than light in the mating of insects. A hidden female moth newly emerged from the chrysalis 

 is often employed b}' the entomologist to attract a crowd of males to the exact spot, where of 

 course they fall victims to their cupidity. Scent alone is the guide in this case. 



The grub of the Glow-worm, as we have said, differs but little in appearance from the mature 

 feinale. On referring to our photograph of the grub, it will be seen to resemble a caterpillar flattened 

 out from above. Like the caterpillar of a butterfly or moth, the body is built up of rings or segments, 

 jointed together and so giving a considerable power of movement in any direction. In the fore-part 

 wiU be seen the three pairs of legs which are the common possession of all insects. From the hind 



Pholos hy] [H. Mnin, F.EM. 



THE MALE GLOW-WORM 



These enlarged photos show the upper and lower surfaces of the 

 beetle in its usual attitude with head drawn in under the shield. 

 The upper figure shows the head extended. 



