silk thread for the first half ring of the temporary case; further threads 

 are added, and the larva thus builds the other side of the half ring, so that a 

 full ring is formed (Figure 115, B). The larva builds a temporary case 

 from the anterior margin, covering it with numerous small particles of 

 detritus; it rapidly covers itself with a temporary case and the use of 

 detritus saves the secretion of the spinning glands. When the temporary 

 case is about half as long as its body, the larva turns about inside the case 

 and bites off a large part of the posterior part of the tube; it then begins to 

 build its definite case (Figure 115, C), which consists of secretion without 

 detritus; this is begun at the anterior margin of the temporary case. As the 

 case consists only of silk, its building is slow and may take eight days or 

 more (sometimes even as long as a month), i. e., much longer than in species 

 covering their case with other material (Carasso and Maillet, 1954). 



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FIGURE 115. Building of the case of Setodes sp.: posture of larva and building 

 of supporting base (A), supporting ring (B), completed case (C) (after Carasso and 

 Maillet) 



The larva of Oxyethira (Hydroptilidae)* begins to build its case at 

 the 5th stage; it begins by making a supporting ring of detritus and silk 

 threads (Figure 116); this ring, which is loosely attached to an alga, is the 

 initial structure which replaces the supporting base of Integripalpia and is 

 the first stage of the building of the bottle- shaped case. The neck of the 

 bottle is the anterior margin of the ring, the bottle- shaped part of the case is 

 the posterior part; the detritus on the ring gradually disappears, but its 

 traces remain visible for some time. 



The larvae of Agraylea build the case among algae; they select a 

 straight filament as base for the case. The larva bites off a part of the 

 filament and attaches its ends to the margin of the base so that the filament 

 forms a bow; the space between the filament and the base is filled with silk 

 threads which also envelop the curved filament. The larva then builds the 

 two laterally connected valves of the anterior half of the case, whose inner 

 walls are then strengthened with a dense mesh of silk (Figure 117); the 



* The structures of Hydroptilidae are described after Nielsen (1948:145-163). 



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