FOOD OF CRUSTACEA, CENTIPEDES, INSECTS 01 



Leeches have many enemies — water rats, voles, tlic larvae 

 of the Dytiscus beetle, the larvae of Ilydrnpliilus, the Nepa 

 or water-scorpion, the larvae of the draoon-lly and the adult 

 Dytiscus — all feed upon them. Many birds also eat leeches; 

 and it is recorded that at one artificial leech-farm, where 

 there were 20,000 leeches, they were all eaten up in twenty- 

 four hours by an invasion of ducks. Frogs and newts also 

 devour them and they are not above eating their own brothers. 

 Aulostoma will devour its own species as readily as it will an 

 earthworm. 



Crayfishes, which still lurk in the banks of some of our 

 streams, have a very varied diet, living on dead animals or 

 plants, worms, and the fresh-water alga, Chara, not a very 

 edible vegetable, for it has a most unpleasant smell. So un- 

 pleasant is it that when grown in water in which mosquito 

 larvae are living it proves fatal to them. Many of the smaller 

 Crustacea feed on algae, protozoa and other aquatic organisms. 

 Amongst these there is one large group of small forms called 

 the CoPEPODA which in their turn form the food of many 

 marine and fresh- water fishes. They exist in enormous numbers 

 and play a great role in the economy of the sea. A curious 

 crustacean, the barnacle, is fixed on rocks or often to the 

 bottoms of ships. The larva is free-swimming, but the adult 

 lies on its back and literally kicks its food towards its mouth 

 by the action of its six pairs of legs. 



Some centipedes are carnivorous, but others are vegetable 

 feeders, and one of the so-called wireworms, lulus terrestris, 

 often found in our country curled up under stones, does much 

 damage by gnawing the tender roots of plants. Cockroaches 

 will eat almost anything that man can eat and a great deal 

 more, for instance other insects, such as the common silver- 

 fish Lepisma, paper, leather, paste, refuse of every kind, and 

 even the dead bodies of their companions. They are also said 

 to devour bed-bugs in spite of the unpleasant smell of the 

 latter, and this habit is shared bv a small black ant from 

 Portugal. Dragon-flies, both in their larval and adult stage, 

 will eat only living organisms. Like "living flashes of light" 

 they hawk through the air, catching other insects in flight; 

 whilst their larvae, more or less buried in the nuid, devour 

 worms, insect-larvae, small fish and tadpoles. 



