274 NATURAL HISTORY OF AQUATIC INSECTS CH. 



abdominal segments, or rather from the membranous 

 inter-segmental spaces just in front of them, stand 

 out as many pairs of long, tapering, five-jointed 



B 



FIG. 85. Mouth-parts of larva of Sialis. A shows, in order from without inwards, 

 the antenna, mandible, maxilla, and labium. B, the mentum (base of labium). 



appendages. 1 These are fringed on opposite sides 

 with hairs in regular series, and each is traversed by a 

 sinuous, branching tracheal tube. A stream of blood, 



1 Pictet (Ann. Sci. Nat. ZooL, 2* Serie, V. pi. 3) shows eight 

 pairs of four-jointed gills, and his figure has been copied by 

 other authors. Roesel has the right number, viz. seven, but his 

 figure is too small to show the number of joints. 



