596 



THE NATURE BOOK 



botanical laboratory of one of our leg-like processes, some of which undoubt- 

 universities some years ago, and ultimately edly serve as breathing organs. When 

 escaped into the nver. It is a plant that alarmed by the approach of danger from 



■' ' ' above, the Whirhgig beetle ceases its 

 circhng movements, and instantly plunges 

 beneath the surface, taking with it a 

 large air- bubble wherewith to supply 

 its needs during its temporary absence 



from the surface. 

 The Great 

 \\'ater Beetle 

 [Hydrophilus) is 

 one of the largest 

 of our British 

 beetles, and while 

 it somewhat re- 

 sembles Dytiscus 

 in general ap- 

 pearance, differs 

 from it com- 

 pletely in habits, 

 for it is sluggish 

 in its m o V e- 

 ments, and is a 

 vegetarian. It 

 is of uniformly 

 deep black col- 

 our, and more 

 convex in shape 

 than Dytiscus. 

 Hydrophilus also 

 rises to the sur- 

 face to take in its air supply ; it comes up 

 head first, and by a peculiar movement 

 of the antennre causes the air to descend 

 to the fine hairs that clothe the thorax 

 or chest, and these in turn pass it on 

 to the openings of the breathing tubes. 

 Curiously enough, although a vegetarian 

 in the adult stage of its existence, as a 

 lar\'a Hydrophilus is carnivorous. 



During the spring and early summer 

 arranged that it may practically be said v;e may frequently see at the bottom of a 

 to have four, the lower pair looking down clear shallow pool the untidy bundle of 

 into the water, while the upper look small twigs, or lea\-es, mo\'ing slowly 

 upwards. The result is that while with and cautiously along, which indicates the 

 the lower pair of eyes the \Miirligig presence of Caddis- worms.* It is a very 

 watches for its prey or for the approach interesting experiment, carefully and with- 

 of an aquatic foe, it can at the same time out injury, to rob a Caddis-worm of its 

 keep a sharp look-out with the upper pair tul:)e, and to place it in a saucer of water 

 for any feathered foe that might swoop containing some fragments of twigs, lea\-es, 

 down from above. The larvae of the sand. etc. The insect will at once set to 



makes very rapid growth under suitable 

 conditions, by throwing out young shoots 

 and roots from the main stem, so that a 

 small piece thrown into a pond soon 

 establishes itself and becomes a dense 

 tangled growth. 

 Moorhens, wild 

 duck, and geese, 

 as well as the 

 D}i:iscus beetles, 

 get their legs en- 

 tangled in the 

 weeds, with the 

 result that small 

 pieces of the 

 brittle stem are 

 detached and 

 carried away to 

 the next pond or 

 stream, as the 

 case may be ; 

 and in this way 

 the plant has 

 spread to nearly 

 every pond and 

 stream in Eng- 

 land. 



Dytiscus has 

 several interest- 

 ing though smaller relations, denizens of 

 the pond, who are more oval in shape, 

 and, although of lesser size, equally 

 rapacious. 



A curious and interesting beetle is the 

 \\Tiirligig, which has gained its popular 

 name from the quaint, rapid, gyrating 

 movements it performs upon the surface 

 of the pond. The position of the eyes at 

 the side of the head of this beetle is so 



THE SPIRACLES THROUGH WHICH THE DYTISCUS 

 TAKES IN ITS SUPPLY OF AIR. 



Whirligig are very quaint-looking crea- 

 tures ; they somewhat resemble small 

 centipedes, owing to the body segments 

 being furnished on each side with slender, 



work to collect the pieces of twigs, and 

 weave them together into a new protecting 

 garment. F. Martin Duncan. 



*Spe page 571. 



