SUBAQUEOUS LIFE 203 



apparatus covering the mouth like a mask. They 

 are sluggish creatures, crawling on mud or weeds, 

 and slowly swimming, depending on their dingy 

 colouration to enable them to lie in wait for 

 passing insects. Some of them have the power 

 of making a pounce forward by the sudden ejection 

 of a jet of water from their tails, but most of them 

 rely on stealth and the mask for making captures. 

 This mask can be shot out swiftly like a jointed 

 arm, bearing a formidable prehensile weapon, armed 

 with a pair of sharp pincers or toothed jaws; Woe 

 to the luckless Chironomus or ephemerid that comes 

 within reach of this terrible trap ! There could 

 hardly be a greater contrast between two stages of 

 the same life as exists between the skulking, inactive 

 larva of repulsive aspect, and the darting, soaring, 

 glittering dragon-fly. Yet both are equally 

 voracious ; the perfect insect generally will be found 

 to have his mouth stuffed with small flies caught in 

 hawking. 



Most aquatic larvae have hideous forms and for- 

 bidding features. Take, for instance, one of the 

 commonest and most rapacious the Dytiscus, one of 

 the water-beetles. Seizing its prey with a pair of 

 sharp, curved mandibles, the blood of the victim 



