Tipidoidea 375 



at most a few) filament deep over the filter paper. Mosses and liverworts 

 should be strewn in as thin a layer as possible. If the culture dishes are 

 placed in a strong north light the plants will remain green and suitable 

 for food for a maximum time — several days to a week or more for the 

 algae, several weeks to indefinitely for the mosses and liverworts. If more 

 than a very few or very young larvae are present, the plants will be 

 eaten more rapidly than they will spoil. Frequent inspections are ad- 

 visable and fresh material must be added as needed. Accumulations of 

 detritus are not harmful unless considerable quantities of plant material 

 are undergoing rapid decomposition. Young larvae, in fact, appear to 

 thrive best on a thin, brownish-green detritus that accumulates from the 

 decomposition of a small excess of plant material. The newly hatched 

 larvae of L. distorts, L. rostrata, D. subalbipes, T. caloptera, and others 

 do best on detritus from algae or mosses, or on algae, but may be fed on 

 mosses after they have reached the 2nd instar. Stock supplies of 

 algae, mosses, and liverworts may be maintained in large jars or aquaria 

 that are kept in strong, diffused light. Almost any species of filamentous 

 or colonial alga that is available appears to be satisfactory for food. 



GROUP V. THE LARVAE AQUATIC, PUPAE AQUATIC OR SEMI-AQUATIC 



Since it is generally tedious and expensive to simulate aquatic, espe- 

 cially lotic, habitat conditions in breeding cages, Group V includes only 

 the residue of aquatic species that may not be reared or cultured by the- 

 methods used for groups II and IV. 



Some or all of the known larvae of the various species of Dicranota, 

 Hexatoma, Pedicia, Protoplasa, and Longurio live in the gravel, sand, or 

 sandy silt of rill, creek, or shallow river bottoms and margins but mi- 

 grate well above the water-line to pupate. The larvae of Dicranota, 

 Hexatoma, and Pedicia are predacious and very active. Half grown or 

 older larvae of Hexatoma juliginosa, H. aurata, H. tristis, Pedicia in- 

 constans, P. johnsoni, and P. paludicola have been carried through to the 

 adult stage in rearing jars in which wet sand or sandy gravel was piled an 

 inch or more above the water-line on one side of the jar. Water from a 

 reservoir was allowed to drip slowly onto this emergent bank, while 

 a low water level was maintained in the jar by means of a constant- 

 level siphon. These larvae were all provided with tubificid or lumbriculid 

 worms for food. 



Tipula abdominalis larvae, 6-8 mm. long and probably early 2nd 

 instar, have been carried through to the adult stage in a small artificial 

 sand-bottom stream. A stream course with emergent banks was molded 

 in coarse wet sand in a cypress trough, 3 feet by 2 feet by 10 inches deep. 

 The trough was nearly divided longitudinally by a wooden partition 

 so that about 6 feet of stream course, in the form of a "U" was provided. 



