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THE ADAPTATIONS OF AQUATIC INSECTS TO THEIR 



ENVIRONMENTS. 



BY 



Gordon Dalgliesh. 



That all insects were at one time terrestrial is the opinion of most Zoologists, 

 and the means by which many have adapted themselves to an aquatic life is 

 one of the most interesting of Biological studies. Few insects are strictly 

 aquatic in the true sense of the word, some being only so for a period of their 

 lives, others making use of the upper world for respiration or for purposes of 

 migration from one spot to another. No insect when fully adult breathes air 

 dissolved in water. Water clear as crystal supports various forms, while again 

 others can only exist in water which is so putrid with decaying matter as to 

 render the stench arising from it insupportable. From an economic point of 

 view the larvae of many aquatic species are useful to mankind in keeping 

 pure the waters of pools or ponds that would otherwise become disease-laden. 

 Professor Miall tells us that the eggs of a species of Corixa are used as an 

 article of diet by Mexicans. These eggs are ground up with meal and made 

 into cakes. 



For the study of aquatic insects some sort of vessel made of glass is abso- 

 lutely essential for observation at home, the most useful being a bell jar which 

 should be filled with pond water and plenty of aquatic weeds to keep the water 

 fresh. It must, however, be borne in mind that only certain species can live to- 

 gether in harmony, the carnivorous and rapacious species such as many water 

 beetles and their larvas must be isolated. A good compound microscope and 

 pocket lens are of great service for watching in a dead or living state many 

 species. For the observation of small aquatic larvas under the microscope a 

 " life slide " is necessary. 



These are sold by all dealers in microscopic appliances. The most useful 

 I have found being the " Darlston Life Slide".* This is made of vulcanite, 

 measuring S^ x - inches and has in the middle a shallow oval depression of 

 glass for the reception of water and insect. When all is ready for obsei-vation 

 a glass slip covers the cavity in such a manner as to render leakage impossible. 

 This slide will be found of great service in watching the respiration of Ephe- 

 mera and CuUcidcG larvae. For the formation of a collection of aquatic 

 insects two nets will be required. One, the water net, should be made of 

 stout muslin in the form of a wide but not too deep bag. The bag fits on to 

 an iron ring, this fitting into a brass socket which is attached to a stout stick 

 of suitable length. This is solely for aquatic work and should be used freely 

 in sweeping about the weeds and for capturing any insect on the surface. The 

 second net required is the ordinary '* butterfly " net, the bag being made of 

 the finest muslin possible, and yet strong enough for the capture of the swift 



*To be obtained from Mr. Thos. Baltou, Bilshall Heath Rd., BirininKham. 



