NATURAL HISTORY STUDIES 



insect, who has spent the winter in hiding, lays 

 two or three hundred eggs on an early morning in 

 spring. She does so in such a way that they form 

 a tiny raft about a quarter of an inch across 

 which floats on the surface of the pool, and can 

 neither be sunk nor wetted. Each egg is somewhat 

 cigar-shaped, with the upper end pointed, and the 

 lower end with a lid, which opens to let the larva 

 out into the water. The larva spends most of its 

 time hanging head downwards from the surf ace - 

 film, through which it raises its breathing-tube. 

 Very delicate hair-like organs sweep microscopic 

 particles into the mouth. If you push the larva 

 below the surface it sinks to the bottom, but it 

 soon jerks itself up again tail foremost. There are 

 no limbs, but the tail part strikes the water vigor- 

 ously, and there are tufts of bristles on the sides 

 of the body. 



The larva feeds and grows and moults, and after 

 three or four moults it is full-grown almost half 

 an inch in length. It then passes into a pupa 

 stage, very different from the larva, and within 

 the pupa-skin the change from larval to adult 

 structure, which has been in progress for some time, 

 is accomplished. The pupa has a strange shape, 

 with a big " head-end " that seems all out of pro- 

 portion, and with a paired paddle at the hind end. 

 It rests at the surface, head upwards, breathing 

 by two horn-like or trumpet-like tubes. It does 

 not eat at all, and when it is alarmed it has to dive 

 forcibly downwards, so buoyant is its body. After 

 three or four days of pupa-hood the cuticle or outer 



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