50 The South Australian Naturalist. 



NOTES ON THE FORMS AND HABITS OF AQUATIC 



INSECTS.— PART I. 



By Herbert M. Hale (South Australian Museum). 



The conventional idea of an aquarium is a few goldfish and 

 a glass bowl, in which the necessity of daily changing the water 

 is a decided nuisance. It is, however, quite a mistaken idea to 

 imagine that fishes must be kept to make an aquarium interest- 

 ing. Many insects spend the greater part of their existence, 

 or their immature stages, in the water ; very little is known of 

 some aquatic larvae : indeed, it is not always certain to what 

 species they belong. The habits of these insects, the manner 

 in which they obtain oxygen, and their methods of breeding 

 are intensely interesting. An aquarium is a decided asset to 

 the entomologist, and in the study of aquatic insects, or those 

 in which the larval stage is spent underwater, it becomes a 

 necessity. 



The fitting up of an a(iuarium is quite a simple matter. 

 Almost any clear glass receptacle will do for the vessel — the 

 accumulator jar, as used by electricians, is excellent, and even 

 the smaller fruit jar can be made use of. Some well-w^ashed 

 sand or gravel is placed in the bottom, and a few water-plants 

 are installed. The water will then keep perfectly clear and 

 pure, and if no decaying organic matter or other deleterious 

 material is present, will remain so indefinitely, and need never 

 be changed. A sheet of glass on the top of the jar keeps out 

 dust and, provided that the inmates are fed regularly, the little 

 underwater world will maintain itself without further atten- 

 tion. 



Some Australian insects have aquatic larvae, but compara- 

 tively little is known of their life histories ; often such a species 

 in the immature stages is not recognised by the entomologist, 

 and thus there is scope for ample research work. Mr. R. U. Till- 

 yard, when working on the Australian dragon-flies, found the 

 aquarium indis|)ensable, and mentions the fact in his book on 

 "The Biology of Dragon-flies.'' A few years ago the writer 

 obtained some curious unknown maggots from the River Mur- 

 ray, and these, contrary to expectations, proved on hatching to 

 be the larvae of a fly. 



The term "aquatic" insect may be applied to any which is 

 adapted to spend all or part of its existence beneath the water. 

 Now, oxygen is necessary for the well-being of all insects, and 

 the various organs must be constantly bathed in air ; this being 

 so, it will be well to study the respiratory system before pursu- 



