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XXII. Note on the habits of Chironomus (Orthocladius) 

 sordidellus. By Thomas Harold Taylor, M.A., 

 F.E.S. 



[Read October 7th, 1903.] 



The larva of this insect lives submerged in brisk streams. 

 It has the usual structure of a bloodworm, but like other 

 surface-feeding Chironomus-larvffi, it is greenish in colour, 

 and lacks the ventral oills on the last segment but one. 

 When full-grown it measures 7 mm. in length. This 

 larva constructs for its abode a hollow cylindrical tube, one 

 end of which it attaches to the surface of a stone, leaving 

 the other end free and open. The material of the tube is 

 furnished by the secretion of the salivary glands without 

 any admixture of foreign substances. Within the long 

 and flexible silken tube the larva may be seen creeping to 

 and fro, or, if stationary, bending its body up and down in 

 the undulations often practised by tube-dwelling larva3, 

 as a means of renewing water which has been vitiated by 

 respiration. Pure water is admitted by special inlets, 

 which may be either mere slits or roundish holes. The 

 food of the larva consists of unicellular and filamentous 

 algge. Although these grow in abundance on tlie stones 

 around, the strength of the current, and the incessant 

 oscillations of the tube make it a matter of some difficulty 

 for the larva to browse upon them. But since the tube 

 itself soon becomes overgrown with diatoms and other 

 microscopic alga;, the larva, thrusting its head out of the 

 terminal opening and holding on by its anal feet, is able 

 to search the exposed surface of its own tube. The range 

 of its body is of course very small, but the tube is flexible, 

 and admits of being bent upon itself or even doubled in 

 two. By reaching out, the larva can draw up to its mouth 

 any part of the surface of its tube, which thus not only 

 affords lodging, but board as well. 



When the larva is full-grown, it transforms the old tube 

 into a pupal case. It letains the free end for its abode, 

 and converts the rest into an anchoring strand by drawing 

 the sides together with threads of silk. The free end 

 becomes dilated into an oval chamber, the terminal aper- 

 ture of which is somewhat more narrowed than in the 



trans, ent. soc. lond. 1903. — part iv. (dec.) 



