g SPONGILLA-FLIES — PARFIN AND GURNET 437 



liiger towards the eighth segment), whereas those of the eighth seg- 

 r)nt become stout and bear five setae, 



Ventrally on each of the first seven abdominal segments is a pair 

 c jointed external tracheal gills containing two trunks that pass 

 f.'ward and medially, appearing to unite in the longitudinal 

 (Qter of the pro thorax (according to Brown, 1952, p. 145). 



Third-instar larva (fig. 3,d): The specimen of S. vicaria from 

 te Cornell collection measm-ed 3.2 mm. exclusive of jaws, the jaws 

 ling 1.4 mm. long; the Sisyra specimens from Douglas Lake, Mich., 

 mged from 3.6 to 6.0 mm. exclusive of jaws, the jaws from 1.4 to 

 :d mm.; the larvae of C. areolaris ranged from 1.8 to 5.1 mm., the 

 jvvs being 0.9 to 1.1 mm.; those of C. californica ranged from 2.8 to 

 ^5 mm., with the jaws being 0.9 to 1.5 mm. in length. Withycombe 

 1,923, p. 522) gave 5 mm. (exclusive of jaws) for a full-fed S.Juscata 

 ( terminalis larva. Berg (1948, p. 145) stated that the larvae of S. 

 jscata (probably third-instar) reached their largest size, 6.5 mm. 

 i xclusive of jaws), in the autumn (Susaa River, Denmark). Both 

 ',^aria and areolaris larvae which recently molted were hardly longer 

 tan a full-grown second-instar larva. The tubercles and setae on 

 le just-molted third-instar larvae appeared considerably longer than 

 lose on more fully fed or migrating larvae. The jaws are greatly 

 ngthened, more slender in comparison with the rest of the body, 

 lore flexible, and can be readily bent at their apices. 



The antennae are also greatly elongated and at times there is 

 iriation in the number of segments (one or two) and in the lengths 



corresponding segments in the two antennae. The antennae of 

 caria consist of 15 segments in one specimen examined; they are 

 roken on all the other specimens. Anthony (1902, p. 620) found 

 5 segments in most specimens that she examined. The antennae of 

 xolaris consist of about 16 segments, and there are about 14 in 

 ilijornica. The segments beyond the basal, with the exception of 

 le apical ones, are of almost equal diameter, and show variations in 

 ngth, although being almost equal. In one specimen of areolaris 

 iamined, there were 14 segments in the left antenna and 16 in the 

 'ght, with the lengths as in table 3. 



In both Sisyra and Climacia the three terminal segments bear one 

 r two small spines, the antepenultimate segment bearing at its 

 istal end the longest, which runs parallel with the last two segments 

 ig. 3, G, h). The penultimate segment also bears distally a shorter 

 pine running parallel with but barely reaching the distal end of the 

 ist segment. At the distal end of the terminal segment are two 

 pines, both shorter than the penultimate spine, the much shorter, 

 linute one from the opposite side in areolaris and terminal in vicaria. 

 'he terminal segment appears to be longer, thicker, more curved, 



359326—56 3 



