Marvels of the Universe 



but there is one very significant fact which cannot be 

 passed over. It is that, whilst the \-ery large and 

 irregiilar-shaped Xebul;e are those which have especially 

 3-ielded proofs of being gaseous in their nature, there is a 

 class of small Nebulae known as " planetary Nebulae " 

 which also give indications of being gaseous. These 

 Nebulffi received their name from the fact that they have 

 somewhat the appearance of planets, being as a rule very 

 small and of circular outhne. 



The fact is also noticeable (though what its significance 

 may be w-e know not), that these planetary Nebulae are 

 not distributed indifferently over the heavens, but are 

 chiefl}^ to be found in or close to the Milky Way. 



Whilst the gaseous Nebulas jdeld spectra of bright lines 

 differing from one another, and the existence of the bright 

 lines constitutes the proof of their gaseous character, the 

 resolvable Clusters of stars give spectra which, though 

 feeble, are continuous — a phj'sical fact which carries a 

 meaning of its own. 



549 



THE GREEN TORTOISE OR HELMET 

 BEETLE 



BY JOHN J. WARD, F.E.S. 



The scene is a piece of waste ground with low herbage, 

 chiefly consisting of clumps of thistles and flowering, 

 white dead-nettles ; and amongst those clumps you can 

 find the Tortoise or Helmet Beetles at home. 



The insects are inconspicuous when resting on the 

 leaves, since they are green in colour and somewhat flat- 

 bodied. There is, however, no difficulty in identifying 

 them when once they are observed, for in a moment it 

 becomes plain how they acquired their popular names. 

 The broad and sUghtly convex shell which encases the 

 beetle extends considerably beyond the body which it 

 covers, and at once gives one the impression of the 

 covering shell of a tortoise, although the beetle is only 

 about one-third of an inch in length. It looks still 

 more tortoise-Uke from the fact that its head is hidden 

 from view owing to the curious development of the thorax, 

 or central division of its anatom}', which has become 

 dilated so as to cover the head of the beetle ; hence, 

 too, its name — Helmet Beetle. 



Having discovered and recognized the quarry, the next 

 thing is to inquire what purpose the beetles can have 

 amongst the thistles and dead-nettles. Their occupation 

 there is largely that of seeking their mates and the de- 

 positing of eggs by the female insects. 



Plioln 60] [H'lffh Main. A.,*., F.E.S. 



THE TORTOISE BEETLE. 



The full-grown grub of the Tortoise Beetle (natural 

 size). Notice the curious forked appendages. 



I'hoto 6v] imoh Main, B.Sc, F.E.S. 



THE TORTOISE BEETLE. 



Showing its remarkable method of self -pro- 

 tection, which is to hold its food-waste by means 

 of these forks over its body and so conceal itself 

 from its enemies. 



