206 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



and bifurcated), with the integument tending to differentiate papilli- 

 form or hairlike processes and reduce conversely the length of the 

 hairs of its normal thricotaxis; the thoracic and abdominal legs are 

 absent or sometimes partly replaced by "ambulacral areolae," which 

 cannot be explained in any way as neo formations or residues of legs. 

 These larvae, as we have said, are plasmophagous and bore rather 

 low and subepidermal or epidermal mines. 



Near these, however, we find others in which the process of trans- 

 formation appears less advanced and shows us the way that has been 

 followed in arriving at the extreme conditions. 



It is unnecessary to dwell upon the cruciform larvae of the second 

 phase, but the others are worth particular attention ; they are peculiar 

 subcylindrical larvae, normally consisting of the head and the usual 

 segments, which, however, do not project on the sides ; moreover, they 

 are astomous, aphagous, anophtalmous, and apodous with a highly 

 reduced thricotaxis ; in the broad, shortened head capsule without hind 

 processes and with apodemes nearly obliterated, the antennae look 

 like small membranous cups ; the labrum is atrophic and coalesced 

 with the clypeal region ; the mandibles are subatrophied and united 

 with the cranial wall ; the maxillae also are intimately united with 

 the postlabium, but furnished with palpi ; the labium is furnished 

 with palpi and spinneret ; the mouth opening is absent. If these larvae 

 had not a well-defined function, that of constructing the cocoon, we 

 should be tempted to consider them as quiescent forms with involute 

 anatomy. 



The passage from the first to the second larval phase, as it has 

 been pointed out in Lithocolletis Stgr., occurs through a mechanism 

 that externally does not differ at all from the process of moulting of 

 the former and later instars. 



What can we deduce from the modifications of structure very 

 briefly outlined above? Even now it is necessary to acknowledge 

 that in a broad sense an endophytic (more exactly endophyllous) life 

 does not require that the larvae, which have to live it, undergo any 

 modification, when a strictly plasmophagous diet has not been con- 

 sidered as a necessity (and it is not understood why it should be so 

 considered). But if we admit such necessity or consider the fact in 

 itself that there are actually larvae mining leaves in the above- 

 mentioned way, we must acknowledge that : ( i ) the above-mentioned 

 larvae have reduced or eliminated all that was unnecessary or cum- 

 bersome to their movements and dietetical activity in the special 

 microhabitat where they abide; (2) they have displaced the organs 



