JOURNAL 



OF THE 



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Vol. XXI. MARCH, 1913. No. 1. 



FACTORS IN AQUATIC ENVIRONMENTS.^ 



By Frank E. Lutz, 

 New York, N. Y. 



There is little in nature which is hard and fast; few distinctions 

 are clear-cut. Therefore, in a study of environments we must not 

 expect to be able to draw definite lines even at the most evident boun- 

 daries. On first thought it would seem easy to classify environments 

 into aquatic and terrestrial, but, not only are some animals distinctly 

 aquatic at one stage of their existence and. just as distinctly terrestrial 

 at some other, but certain situations such as the mud along a pond's 

 edge are intermediate in more senses than one between water and 

 land. 



Considering the former difficulty, we find that whenever an insect 

 has both terrestrial and aquatic stages, the larval condition is always 

 aquatic. The terrestrial stage, the adult stage, is used merely for the 

 perpetuation and spread of the species. In fact, it will greatly sim- 

 plify matters throughout the study of the relations of insects to phys- 

 ical environments if we keep in mind that the presence or absence 

 of the environment suited to the immature stages determines the pres- 

 ence or absence of the species much more than does an environment 

 especially suited to the adult. 



For the most part, but not exclusively so, aquatic animals are 



* During the past v 'nter the N. Y. Ent. Society has been conducting a 

 series of symposia upon the Relations of Insects to their Environment. The 

 papers on Aquatic Insects published here were given at the first symposium 

 of this series. 



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