28 PROCEEDINGS MANCHESTER INSTITUTE 



given locality. In the collection of the Manchester Institute of 

 Arts and Sciences the Anisoptera alone comprise 28 species, dis- 

 tributed among 16 genera and 4 sub-families. The specimens 

 were gathered within the radius of an easy walk from the city, and 

 it is certain that were the radius extended to twenty miles the 

 result would be the addition of several genera — and probably of 

 one sub-family, the Cordulegasterinas. The cannibalistic habits 

 of Dragon-flies, both in the nymph and imago states, combined 

 with the tremendous external pressure of the many natural checks 

 to increase, have resulted in so marked a separation of the types 

 that with a few exceptions, such as Libellula pulchella, Diplax 

 rubicundula and Gomphus exilis, which are common everywhere, 

 each species may be said to have its particular brook, or pond, or 

 series of pools, or its special season. It is obvious, therefore, that 

 when a marsh is drained, a pool filled, or a brook condemned to 

 servitude as part of the drainage system of city or village, a spec- 

 ies formerly abundant may become extinct in a given locality. 

 Another potent factor in the extinction of species among Dragon- 

 flies is the introduction of new and strange varieties of fish to our 

 ponds and streams. Between the Odonata and the old-time deni- 

 zens of our waters there had come to be, if not an entente cordiale, 

 at least a fnodus vivendi ; but the new-comers, with the eyes of 

 travelers, view everything from a novel standpoint, to the disad- 

 vantage of the Dragon-flies. The extent to which the introduction 

 of German carp, feeding upon muddy bottoms, may be responsible 

 for an increase in the number of mosquitoes, presents an interest- 

 ing subject for investigation. 



The above considerations indicate the desirability of a careful 

 study of this interesting group of insects, that collections and 

 records may be preserved for future students, who may find it 

 difficult or impossible to secure specimens which may now be ob- 

 tained with comparative ease. In some states, notably Massa- 

 chusetts, New York, Pennsylvania, Ohio and Louisiana, this work 

 has already been done with a tolerable degree of thoroughness. 

 In the last-named state an effort has been made to interest the 

 children of the schools, nets and full instructions for collecting 

 and preservation being furnished the teachers in many parishes, 



