376 CHARACTERS OF INVERTEBRATE ANIMALS 



about equal size, and the long body is handsomely marked and 

 coloured. The freely movable head is provided with very small 

 antennae, a pair of huge compound eyes, three simple eyes (ocelli), 

 and biting mouth-parts. Dragon- Flies catch other insects on the 

 wing, and their flight is exceedingly rapid, making them the 

 swallows of the insect world. The eggs are laid either in water 

 or attached to water-plants, and from them extremely voracious 

 aquatic larvae hatch out, which are distinguished by the possession 

 of an extremely long transversely -jointed lower lip. This is 

 usually known as the "mask", because when not in use it is 

 folded up in front of the face, from which position it can be 

 suddenly shot out for the capture of small animals. The action 

 has been compared to that of an old-fashioned carriage -step. 

 The larval condition is maintained for about a year or rather 

 less, during which time a number of moults occur, while towards 

 the end of the period the rudiments of wings make their appear- 

 ance. There is no motionless pupa stage, but the full-grown 

 larva climbs up the stem of some plant till it is above water, 

 when its skin splits longitudinally along the dorsal surface, and 

 the adult dragon-fly, which has been meanwhile forming within, 

 gradually works its way out. Over forty species of British dragon- 

 flies are known, of which the following may be mentioned: The 

 Great Dragon- Fly (sEsckna grandis), a large reddish-brown insect, 

 with lighter markings; the Horse -Stinger (Libellula depressa) 

 (fig. 228), with broad abdomen, light brown, with yellow spots 

 in the female and violet in the male; and the little Demoiselle 

 Dragon- Fly (Agrion puella), with T-shaped head, and slender 

 abdomen, black in the female and banded with light-blue in the 

 male. 



The May-Flies or Day-Flies are fragile insects in which the 

 hind- wings are much smaller than the others, and the abdomen 

 has two or three slender tails attached to it. The adult only 

 lives a short time, though the traditional day may in some cases 

 be extended to a fortnight. The life-history broadly resembles 

 that of the dragon-flies, and the larva of some forms appears to 

 live three years, an unusually long time, contrasting sharply with 

 the brief existence of the imago. Something like 300 species 

 have been described, and common British forms are the Common 

 May-Fly or Gray Drake (Ephemera vulgatd] (fig. 228) and the 

 Green Drake (E. Danica). Some of the most successful lures of 



