AQUATIC MIDGES AND SOME RELATED INSECTS. 21 



is not only capable of living in the same conditions as they, but, as can be shown by a 

 simple experiment, both are able to live on the debris found in a watering trough. 



It seems possible, then, that the difference may consist in such a simple adaptation 

 as in the manner of depositing eggs. Needham (1906) has referred to the habit of 

 Chironomus annularis Degeer of extruding its eggs while in flight and depositing them 

 free in the water. Mundy (1909) has referred to the fact that T any tarsus pusio eggs 

 were found attached to leaves several centimeters below the surface. J. T. Lloyd 

 informs the author that he has observed masses of chironomid eggs of considerable 

 extent blown upon the shore of Cayuga Lake. The author has observed Chironomus 

 hyperboreus Staeger depositing its eggs upon the surface. Some of these females were 

 caught in flight and found to have a considerable mass of eggs ready to be deposited. 

 On the other hand, Chironomus cayugce females were observed just at dusk to light upon 

 small stones which projected slightly above the water level and to thrust the tips of 

 their abdomens beneath the surface of the water and there deposit egg masses attached 

 to the stones. All the eggs taken from troughs have been found attached, and it seems 

 possible that by this habit alone C. cayugce may be especially adapted to such a singular 

 habitat. 



It is interesting to note that troughs fed from flowing streams where a considerable 

 amount of silt is constantly present have in every case been found to contain but few 

 or no larvae, and it seems probable that the choking out or covering up of the food 

 supply is the controlling factor. 



Other members of this group are found in streams, ponds, reservoirs, and lakes, 

 even at very great depths, as in Lac Leman. Here Mile. Zebrowska (19 14) found 

 specimens designated as Chironomus "B" abundant to a depth of 20 meters and rare 

 to the extreme depth of 100. 



THE BURROW. 



The process of building a burrow has probably been observed in this group more 

 frequently than in any other, because the larvae when out of their burrows are very 

 restless and at once begin to rake particles together. The pectinate hairs and comb of 

 the labrum and the epipharyngeal comb are used in this work. The anterior prolegs 

 usually form the limit of the backward stroke of the head, and it is difficult to say for 

 certain that they remove the accumulated debris; but it is clear that this debris is 

 fastened together with silk, and it seems possible that they may be instrumental in 

 spreading it. 



When a certain amount of debris is accumulated, it is raked back by a looping of 

 the body, so that the posterior prolegs hook into the silk that holds the particles together. 

 When a sufficient amount has been so accumulated, the larva seizes the mass adhering 

 to its posterior prolegs by means of its head and anterior prolegs and fastens it over 

 the posterior end of the body in such a manner as to form a narrow band or strap, which 

 is referred to in Group II of Mundy's description. This narrow band has the dimensions 

 of a cross section of a burrow, and with this as a beginning the construction work con- 

 sists of a direct application of building material to either side of the strap. From this 

 stage on the behavior is the same as that observed in the ordinary lengthening of the 

 burrow. The larva now reaches out and grasps by means of its labrum, mandibles, and 

 prolegs a mass of debris and draws it in and puts it in place at the edge of the burrow. 



