548 The American Naturalist. [June, 
of the opposite side but capable of being applied to it so as to 
form a short proboscis. The mandibles (see fig. 5, md, plate 
XXV), of unimaculella are not denticulate, but single-pointed, 
and are not strongly chitinized, functioning rather as flexible 
lobes or plates than as biting jaws. The labium (see fig. 4, plate 
XXV), is truly lip-like, with plainly distinguished sub-mentum 
(sm), mentum (m), and prominent 3-segmented palpi (1, p.) ris- 
ing from the outer or distal margin ofthe mentum. M. purpur- 
ella (see fig. 3, plate XXV), presents a condition of mouth-parts 
very like unimaculella. In anderschella, also, one of the species 
examined by Walter, the outer lobes again of the maxille are 
the ones which seem to me to be free, while the inner ones go 
to form the very rudimentary proboscis referred to by Walter. 
However, without study of other species the question may be 
left a moot one. For the object of this paper the exposition 
already made of the generalized state of the mouth-parts in 
Micropteryz is sufficient. 
_ The condition of the mouth-parts of Hepialus, the genus as- 
sociated with Micropteryx in the generalized sub-order Jugatæ, 
reveals an interesting further confirmation of the naturalness 
of the association. I have examined the mouth-parts of the 
Hepialus hecta, sylvinus, and of an undetermind species. Un- 
fortunately, in this genus we have an atrophied or reduced 
condition of the parts, a functionless state, as so often met 
among Lepidoptera (Bombyz et al). This condition makes a 
comparison of the mouth-parts of Hepialus with those of Microp- 
teryx, or of other Lepidoptera, difficult, but there are sufficient 
remaining evidences of the generally Micropteryz-like character 
of the mouth-parts to justify fully a recognition of. their 
generalized character. Especially is thisshown by the labium. 
In Hepialus sp. (fig. 10, plate XXV), the mandibles are entirely 
reduced, the maxillary palpi (mz. p.), greatly reduced, and one 
of the maxillary lobes lost, although one (mz. /.), remains in 
reduced state. The labium, however, retains its lip-like char- 
acter, with quadrangular mentum and thick, fleshy, 2-segmen- 
ted palpi (Z. p.), very like the similar organ in Micropteryx and 
altogether unlike the fixed sclerite forming part of the floor of © 
the head, the character assumed by the altered labium of the 
higher Frenate (see fig. 9, plate XXV). 
