AQUATIC MIDGES AND SOME RELATED INSECTS. 47 



large size and overlapping broods indicate their possible importance to fish life and in 

 fish culture. 



Group IV contains an aberrant species that feeds directly upon floating aquatic 

 leaves and is noteworthy chiefly for its direct injury to those plants. 



Group V contains at least one species (Trichocladius nitidellus) that promises to 

 be of considerable importance, as it is able to subsist entirely upon filamentous algae, 

 chiefly Spirogyra. 



Group VI includes a number of free-living forms that occupy somewhat unique 

 habitats but constitute a group of minor importance. 



The entire subfamily Tanypinae consists of predacious forms, which as a group 

 apparently do not contribute anything of economic importance to the Chironomidae as 

 a whole. They, however, do occasionally feed upon small Crustacea and the more 

 rapidly moving diatoms and in this way help to counteract their otherwise well-merited 

 position as an economically undesirable group, from the standpoint of the fish-culturist. 



The subfamily Ceratopogoninae are scavengers as a group and as such fulfill a 

 useful function. 



From the consideration of these rather arbitrary divisions, as well as the natural 

 subdivisions of this large family, it becomes evident that there is a wide range in the 

 adaptations of its different members. Some of these adaptations are of generic value, 

 while others seem to vary within the genus, as in Tanytarsus obediens, which is in- 

 cluded in Group I, although the other members of the group belong to the genus 

 Chironomus. In a similar manner the red color of the larvae seems to occur with 

 little or no relation to the genus or subfamily but is rather more closely associated 

 with the nature of the environment. 



It is obvious from the above that the family has become specialized for different 

 habitats. While the author has tried to point out what seems to be the behavior nor- 

 mally characterizing each group, it is easily apparent from a few observations that the 

 great adaptability of all these species when under the stress of adverse conditions reduces 

 them to what is probably the primitive habit of the group, namely, that of direct feeding 

 on the debris about them. 



The degree of departure from the primitive method of feeding, however, varies 

 considerably. In the Tanypinae we have a form that is strictly predacious, while in the 

 Ceratopogoninae we have a form that is adapted to live on dead and even decaying 

 organic matter. The latter group seems to be about as abundantly represented in 

 semiterrestrial environments as in those that are strictly aquatic, and it is this group 

 that doubtless contains the most or perhaps the least primitive representatives of the 

 family. The Tanypinae doubtless come next and then the Chironominse. 



In the Chironominse it would seem that from direct feeding by the use of silk to 

 attach together the particles fed upon the use of silk in entangling particles in a stream 

 would be but a simple step. Then, from this beginning an artificial current, made 

 necessary by the poor supply of air, might readily lead up through a series of stages, 

 from the entanglement of particles in the lining of their burrows to the present highly 

 specialized silk net, which characterizes Group I. 



The small size of these larvae and their adaptability to such a wide range of habitats 

 enable them to take possession of an environment where the food supply would be 



