274 NATURAL HISTORY OF AQUATIC INSECTS CH. .\ 



j 

 abdominal segments, or rather from the membranous i 



inter-segmcntal spaces just in front of them, stand i 



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



Fig. 85. — Mouth-parts of larva of Sialis. A shows, in order from without inwards, ;j| 

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



appendages.^ These are fringed on opposite sides | 



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



sinuous, branching tracheal tube. A stream of blood, i 



1 Pictet {A/i/i. Sci. Nat. ZooL, 1^ Serie, V. pi. 3) shows eight i! 



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. 



