The larvae of some Leptoceridae (Mystacides azure a) and 

 Limnophilidae (Anabolia soror) are adapted for life at the bottom, 

 covered with sand and detritus; these larvae build tubular cases 

 covered laterally with conifer needles or coarse detritus consisting of 

 thin twigs (Figure 103). 



Larger species use larger sand grains or small stones (Figure 104); 

 these cases are smooth; their posterior end is rounded or tapering, with 

 a small opening partly covered with a membrane. 



Some cases covered with fine sand (Apatania) bear large sand grains 

 at the sides; other cases (e.g., species of Silo and Go era) are short, 

 sand tubes with wings which consist of flat, laterally projecting stones which 

 make the case heavy and flat. The cases of this type are also typical of 

 inhabitants of moving water of the open surf zone of lakes. 



The cases of the species of Molanna are characteristic for inhabitants 

 of sand and sand- slime lake bottoms; they are flattened and shieldlike 

 (Figure 105) because of the wings at the sides of the straight, conical tube. 

 The cases imitate the sand or sand- detritus bottom so perfectly that it is 

 sometimes difficult to recognize them even in a small aquarium and only 

 their movements betray them. Breakers of medium strength pass over the 

 tube; however, strong surf which is usually avoided by the larvae, which 



70 concentrate in the more or less calm zones, may turn the larval case over; 

 and the larva has to make a great effort to restore its initial position 

 (Figure 76). 



Larvae living on detritus- covered bottom build cases which are often 

 unwieldy structures of coarse vegetable detritus (Figure 106) closely 

 resembling the environment (Limnophilus stigma, L. flavicornis, 

 L. rhombicus, L. politus); these species also use seeds of terrestrial 

 plants, e. g., those of birch, parts of insects and mollusk shells, sometimes 

 large algae, e. g., spheres of Nostoc (Figure 112, B). 



Some larvae of Calamoceratidae (G anon em a extensum) cover their 

 cases with soft wood fragments; they bore a cylindrical hollow in the 

 fragment and live in it (Figure 107). The cases of species living in springs 

 (Crunoecia irrorata) are covered with minute particles of detritus 

 and have a regular tetrahedral shape (Figure 108); cases of mature larvae 

 of Lepidostoma hirtum are similar. 



In plant thickets, the larvae cut fragments of stalks and leaves and build 

 green cases; e. g., the cases of Ph ry g an e a and Agrypnia (Figure 109), 

 the delicate cases of Triaenodes with their spirally arranged plant 

 fragments, the trihedral cases of Limnophilus nigriceps or 

 L. d e c ip i e n s, the leaflike cases of Nemotaulius and Glyphotaelius, 

 the cases of Grammotaulius and other species living among plants. 



The cases of Holostomis and Ironoquia dubia (which live in 

 slow currents) are tubes covered with smoothly arranged plant fragments; 



71 the cases of H al e s u s digit at us are covered with detritus (Figure 11 0) 

 and resemble cases of Potamophylax stellatus (which are covered 

 with sand). 



Building methods of the cases. The structures of caddis flies 



72 have been known for a long time* and have been described repeatedly, but 

 the process of building is known only for few species. 



The larvae of caddis flies were first described by Aristotle as "wooden aquatic worms.' 



64 



