discard 4 or 5 particles until it finds a suitable one. The selected particle 

 is first placed at the anterior margin at four or five different points; while 

 a suitable position is searched for, the particle is repeatedly turned before 

 being glued. When the position has been found, the larva touches the 



76 particle and the neighboring particle alternately with the opening of the 

 spinning glands so that a zigzag suture results (Figure 114, D) gluing the 

 new particle to 2 or 3 neighboring ones. Cracks and hollows between the 

 particles are sealed with silk threads. The construction progresses 

 rapidly; the old part is added to and repaired, and the larva repeatedly 

 retracts into the tube to strengthen the connections between previously 

 laid particles. The net of threads connecting the sand particles becomes 

 gradually denser and thicker, producing a felt (Figure 114, E) which forms 

 the soft inner lining protecting the larva from contact with the sand particles. 

 If a sand particle is attached to the anterior margin of the case, the 

 selection of a particle takes about 9 seconds; the licking of it about 



10 seconds, and gluing a particle with a zigzag suture 30 seconds. If the 

 building is interrupted (e. g., if the previous work has to be repaired) the 

 building of a case takes longer. 



The posterior end of the tube, which was attached to the supporting base, 

 is removed from this when the tube is completed. The larva turns about 

 inside the tube and cuts the threads not far from the posterior end of the 

 tube; together with the supporting base, the larva also cuts off the small, 



77 first part of the tube. It examines the posterior opening of the case, 

 straightens it, and strengthens it with silk threads. 



After an interval the larva begins to build the anterior hood (Figure 114, F) 

 and the lateral wings, using the same process of selecting, examining and 

 connecting the particles; the larva projects from the case almost its whole 

 length and bends posteriorly during this activity. It is impossible to build 

 well under these conditions; the particles are loosely connected to the 

 margin of the wings, and the larva cannot attach wings to the posterior end 

 of the case. It prolongs the tube and adds the wings, and then bites off the 

 posterior part of the tube without wings, building the wings along the whole 

 case. 



The larva of Molanna angustata can rebuild the anterior part of 

 the case if this is removed, rebuild wings, seal a cut in the anterior hood, 

 repair holes in the middle of the case, but is unable to repair damage in 

 the posterior end of the tube (Dembowsky, 1933:271-292). 



Cases made of secretion are built by the larvae of Setodes in the 

 Integripalpia; such cases are built by a number of species of Hydroptilidae 

 in the Annulipalpia. 



When a larva of Setodes (Leptoceridae) is removed from its case, it 

 begins to build a new case, like the other Integripalpia, by forming a 

 supporting base of detritus and secretion; this base is loosely attached 

 by some silk threads to the ventral side of the 1st abdominal segment; the 

 base is kept in position by the fore and midlegs and by the end of the curved 

 abdomen. The larva hangs from a plant with its swimming hind legs; the 



78 fore and midlegs do not have to support the body and are free to be used for 

 building. When the supporting base is completed, the larva moves it to the 

 dorsal side of the 1st abdominal segment (at the point of the mediodorsal 

 process) with its mouthparts, legs and the anal legs. It then lays down a 



70 



