Some Habits of the Adults 27 



twenty-four to forty-eight hours, according to the 

 species, if the ova be stirred up in some way, as by 

 a rain or an animal stepping into the pool, stones 

 dropped in, etc., hatching occurs, often in less than 

 half an hour. The larvae of the same batch will not 

 come out at once, some will keep on emerging, a 

 few at a time, for several hours or days; others will 

 remain quiescent until a second or third stirring up. 

 As the single eggs will resist drying almost indefi- 

 nitely, Dr. Dupree logically concluded that this 

 accounts for the appearance of larvae in a pool 

 freshly formed by a rain where there had not been 

 any water for weeks before. The eggs, laid in a 

 former pool on the spot, have been left on the 

 ground as the evaporation took place. The rain 

 makes a new puddle, the eggs are washed about and 

 shaken up, and, often in two or three hours, before 

 there has been any time for oviposition, laying, and 

 hatching, the pool swarms with tiny larvae. The 

 majority, if not all, of the single-egg-layers winter 

 over as eggs, at least in the North ; the early spring 

 rains, as soon as warm enough, bring out the wig- 

 glers. The fall batches are those which hibernate. 

 In the laboratory it was possible to keep, as it were, 

 larvae " on tap"; agitation of the jar in which the 

 eggs lay being sufficient to produce larvae in a short 

 time, sometimes while still shaking. A weak solu- 

 tion of formalin will hasten hatching, but, naturally, 

 is not healthy for the wigglers. The methods of 

 egg-laying will be discussed under the separate 

 species. 



Dr. Dupree finds that eggs will, if left to themselves, 



