AQUATIC INiSECTS IN NEW YORK STATE 373 



horny with two brushes of hair above, between which is a very 

 small ligula, covered with a small brush of hairs. Fans, com- 

 posed of stout stem, bearing about 46 scythe-shaped rays, lined 

 on the inside by very minute, equidistant, erect hairs of equal 

 length. Thoracic proleg, faintly four jointed, subconical, retractile 

 (introversible), very thin and transparent, crowned with about 

 20 rows of short, sharp hooks, apparently arranged in a circular 

 manner; the hooks, of which 10 are in each row, seem to be mov- 

 able to a certain extent, and are fastened or hinged to small 

 chitinous rods in the epidermis. Tip of abdomen formed by a 

 subcylindric body crowned with rows of hooks. Breathing 

 organs below these hooks and on the upper side of abdomen; 

 they consist of three short, cylindric, soft and retractile tenta- 

 cles, which connect with large internal tracheae. In full grown 

 larvae a spot more or less dark is seen on each side of thoracic 

 joint; it is produced by the formation of the coiled breathing 

 tubes of the future pupa. 



Pupa. General color when fresh, honey-yellow; prothoracic 

 filaments brown, and the abdomen dorsally also tinged with 

 brown, except a mediodorsal space. All the members have also 

 a fine brown marginal line; prothoracic filaments consisting of 

 six main rays, issuing from the basal prominence and subdivided 

 two or three times, so that in most cases as many as 48 terminal 

 filaments can be counted. Abdominal joints three, four, and 

 five, each with eight well separated, dark brown and anteriorly 

 recurved hooks. The four on each side separated by a medio- 

 dorsal space; those on joint 3 less conspicuous than those on 

 joints 4 and 5; joint 6 without armature; joints 7, 8 and 9, and 

 also subjoint less distinctly armed near anterior margin with a 

 continuous dorsal row of very minute posteriorly recurved 

 points; ventrally joints 6, 7, and 8 have each four very minute 

 anteriorly recurved hooks. 



Cocoon. Average length 3.5mm. Not completely made and 

 not entirely covering the pupa, but tightly surrounding its larger 

 portion. Shape very irregular, with no distinct rim at the 

 upper edge, which is more or less ragged. The threads compos- 

 ing it are very coarse, and the meshes rather open and ordinarily 

 filled with mud. Not always fastened separately to objects, but 

 frequently crowded together without forming, however, such 

 corallike aggregations as in some of the northern species. 



That part which Riley called the labium in the above descrip- 

 tion, appears to be a combination of labium proper and the 

 hypopharynx. Often in dissection these two parts stick 

 together and appear as one, but with a little care the hypo- 



