to the substrate with their anal legs; when the larvae of Annulipalpia (which 

 build galleries or nets) crawl, the abdomen is extended and the anal legs 

 51 remain motionless; the larvae rest on them when they wait for prey, 

 bending the abdomen and curving it backward (Figures 73 and 74); this 

 enables them to make a strong forward thrust to catch the prey. The small 

 active larvae of Hydroptilidae are without cases in the early stages, or bear 

 light cases consisting of secretion in older stages; they run rapidly among 

 algae, extending the whole thorax from the case and raising the abdomen. 



;so) 



FIGURES 73 and 74. Modes of movement of free-living larvae 

 of Annulipalpia: 



73 — running larva ofTinodes waeneri (after Hickin); 



74 — posture of a larva of Polycentropus flavomacu- 

 latus waiting for prey (after Wesenberg-Lund). 



FIGURE 75. Larva of Limnophil us flavicornis 



The larvae of Integripalpia which bear cases covered with heavy material 

 move slowly, extending the anterior end of the body from the tube; only the 

 thoracic legs take part in movement; the larvae use the laterally directed 

 claws of the anal legs to cling to the case. Movement with the heavy mineral 

 cases of Po t a m o p hy 1 ax, Dicosmoecus or Goera or with cases 

 covered with mollusk shells and large fragments of wood (Limnophilus 



46 



