AQUATIC INSECTS. 23 



excite our curiosity and interest. The non-case-building forms 

 which spread their nets in the riffles and waterfalls afford oppor- 

 tunities for the most acute observer to discover new facts and add 

 to our literature the wonderful tales of the lives of our hiimbler 

 insect friends. Many of these forms furnish food for our fresh- 

 water fishes and thus are of direct economic importance. Very 

 little is known about this group and it only awaits the keen 

 observer, in love w^ith his work, to add to our stores nf knowledge. 

 It is not necessary for ine to do more than call attention to some 

 of the other aquatic insects. In the Hemljitera are found several 

 families which spend their entire lives in the water. The grace- 

 ful water boatmen (Corisaj the rapidly darting back-swimmers 

 (Notonecta), the long, narrow, slowly crawling water-scorpions 

 (Ranatra), and the giant water-bugs (Belostoma and Zaitha) are 

 vmdoubtedly familiar to all, while the long-legged water stridors 

 (Hydrobatidae) appropriate the surface of the water for their 

 home. In the great order of Lei)idoptera (Moths and Butterflies) 

 are found forms which possess aquatic larvae. Such forms are 

 extremely rare but should be searched for by all lovers of insect 

 life. In the Diptera (flies) there are several large families 

 (Culicidae, Chironomidse, Simuliidee, etc.) in which the larvse are 

 aquatic while the aquatic habit is widespread in the order. Owing 

 to the discovery in recent years that the adults of certain mos- 

 quitoes act a*^ intermediary hosts in the transmission of several 

 serious diseases, malaria and yellow fevers, the Culicidae have 

 assumed a very important place in man's welfare and have been 

 the objects of closest study. Methods have been devised for the 

 extermination of these pests, and places once the centres of 

 malaria and yellow fever are now absolutely free from these dis- 

 eases Time and siiace will not adtiiit of the discussion of the 

 many aquatic insects in this order. In the Coleoptera (Beetles) 

 we find the predaceous diving and water scavenger beetles 

 (Dytiscidee and Hydrophilidse) abundant in our stagnant ponds 

 while The graceful Whirligig beetles (Gyrinidae) perform their 

 vai'ied curves on the surface. Tlie larvae of these forms are 

 interesting creatures and are found in the places frequented by 

 the adults. Several families (Parnidae etc.) are aquntic in both 

 larval and adult stages. The life histories of the aquatic beetles 

 are but little known and the .study, though a diificult one, is of 



