214 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



anterior arms of the tentorium, their different length and position, 

 the oblique articulation of the labrum and different direction of its 

 sclerotized posterior processes, the absence of lanceolate bristles on the 

 left side of the epipharynx and their presence on the right side, though 

 abraded by use, the erosion of the teeth of the right mandible, etc. 

 The thoracic legs are transformed into subpyriform organs, without 

 distinction of the various parts; the abdominal legs are absent, except 

 in the loth urite (which protrudes dorsally and backwardly in an 

 irregular, sclerotized, pigmented, toothed, hairy process), where they 

 are, however, vestigial. This condition is correlated with peculiar 

 procedures in the act of gnawing wood. As a matter of fact the bor- 

 ing larva turns its head, advancing by clockwise windings like the 

 curls of a spire. It is noteworthy that in the new-born and still inac- 

 tive larva the labrum, anteclypeus, and tentorium are asymmetrical ; 

 the lanceolate palatine bristles, present and entire in the right side, 

 are absent in the left side. Similar conditions occur in other larvae of 

 wood- feeding Hymenoptera Symphyta, as for instance those of the 

 large Sirecidae. 



Several Tenthredinidae Phyllotominae and Blennocampinae belong- 

 ing to the genera Phyllotoma Fall., Pelmatopiis Hart., Metallus Farb., 

 Fenusa Leach, Fenella Westw., and others are leaf miners in the 

 larval stage, but generally live within the parenchyma (seldom near 

 one of the two epidermic surfaces), usually bore gall mines and are 

 euholometabolous (here and there we observe a rare exception). 

 Some of these, as the larvae of Pelmatopus mentiens C.G., which may 

 be found in the leaves of the buttercup {Ranunculus), appear little 

 or not at all modified. We may observe only the forward displacement 

 of ocelli and the reduction in length of the antennae which exhibit 

 joints heaped one on another in a special way. In the other above- 

 mentioned genera the modifications occur approximately on the same 

 plane ; the body is moderately flattened ; the head capsule is progna- 

 thous, more or less projecting on the sides, posteriorly attenuated and 

 prolonged in a kind of lamina, which penetrates into the thorax. The 

 invagination pits of the anterior arms of the tentorium are more or 

 less considerably displaced caudad. Ocelli are displaced a little dor- 

 sally and somewhat anteriorly. The labrum is broad, sublaminar, and 

 shows ventrally the epipharynx with conspicuous and lanceolate 

 bristles. In the mouth the mandibles are depressed but not laminar, 

 and the parts forming the maxillolabial complex are well differen- 

 tiated, the integument of its lower surface is almost completely 

 sclerotized, but it does not coalesce with the head capsule as in the 



