OX THE ORAL APPARATUS OF THE LARVA OF WORMALDIA. H7 



spinneret, at whose sides appear minute projections 

 which probably represent the palpi of the second 

 pair of maxilla?. On the upper side of this composite 

 part may be the tongue, with a somewhat concave 

 centre, punctate space behind and hairy space in 

 front; but all the inner mouth parts I have had 

 difficulty in making out satisfactorily. The strong 

 falcate mandibles are much used in the building of 

 the fixed case, but they also suggest a predatory 

 existence ; on the other hand, the form and fringes 

 of the labrum seem to me to point to minute 

 organisms being the usual food. 



Reverting to the retractile abdominal filaments, 

 Pictet claimed these as the exclusive property of 

 what is now considered the typical genus of Hydro- 

 psychidce. viz., Hydropsy che; but they are by no means 

 confined to one group, for, in addition to Wormaldia, 

 they are found amongst Hydropsychidce, also in 

 Tinodes, but not, so far as I have seen, in the 

 group containing Plectrocnemia and allies. Of 

 Rhyacophilidce, Agapetus has them. While there 

 is little doubt that they are breathing organs, it is 

 strange they should be so prominent in Hydropsy die, 

 which is so richly provided with lateral filaments. 

 Nor can they well be the sole organs of respiration 

 in such larvae as possess no lateral filaments. I 

 suspect larvae in the latter condition must have 

 tracts of the integument modified to subserve 

 respiration, as Mr. Eaton has indicated is probably 

 the use of the spaces thickly overrun with tracheae 

 found on the head and prothorax of the nymphs 

 of JEcdyums, &c, in the Ephemeridce, 



Explanation of the Plate. 



Plate II. 

 Fig. 1. Head above, showing labrum much exserted. 



2. Mouth parts from beneath ; (a) labrum, (b) 1st maxilla?, 



(c) spinneret. 



3. Antennae. 



4. Apex of 1st maxilla. 



5. Apex of mandible. 



