348 NEW YOfiK STATE MUSEUM 



threads uniting as they pass between the combs of the dorsal' 

 and Tentral plates, I believe the function of the upper plate 

 to be a press for the silk thread. On each side, extending, 

 dorsad and caudad, is a chitinized, hornlike process. Only the 

 fringe of hairs of the hypopharynx is visible when the larva is 

 viewed from below_, the rest being covered by the labium. The 

 suture between the labium and the ventral surface of the head,, 

 indistinct in some species, seems entirely wanting in others,, 

 and therefore, the labium is immovable. The cephalic margin 

 of the labium is furnished with regularly placed teeth; the 

 arrangement of which, together 'with the number and arrange- 

 ment of the setae on the ventral surface, furnishes some excel- 

 lent specific characters. Since, in order to identify a species,. 

 it is necessary to dissect out the mouth parts, a few words in 

 this connection will not be out of place here. If the specimen, 

 either fresh or alcoholic^ be placed on its side, and with a 

 scalpel a frontal cut made through the head, passing just below 

 the eye spots separating the dorsal from the ventral surface, 

 then, placing the sections with the cut surface uppermost, the 

 mouth parts may be readily picked out with a needle. In the 

 ventral part will be found the maxillae, the hypopharynx and 

 the labium. The hypopharynx lies very close to the labium and 

 therefore requires some care to remove it. In the dorsal part 

 will be found the fans, the labrum, and the mandibles. If the 

 cut be made too far toward the dorsal surface, the mandibles 

 will be attached to the ventral part, and the labrum will prob- 

 ably be destroyed, since it lies at right angles to the axis of 

 the body, overhanging the mouth opening. The separate parts 

 may then be dehydrated, cleared, and mounted on a glass slide. 

 The single thoracic proleg attached to the ventral surface 

 of the first (or second?) segment is an elongate, truncate, conical 

 process, at its extremity with a number of rows of hooks, 

 similar to those found at the anal end, to be described later. 

 The use of this proleg has already been mentioned. From a 

 narrow, slitlike opening on the dorsal surface of the last seg- 

 ment of the body are projected the retractile, translucent^ 



