Hubbard.] 668 [April 18, 
has a cylindrical body of twelve segments; a globular head, with two 
large ocelli, which are, however, covered by the epidermis ; the first tho- 
racic segment is enlarged, and partly covers the head, like a hood ; the 
three thoracic segments bear well-developed legs ; and the abdomen termi- 
nates in a long tapering style, toothed and concave on the upper surface, 
and turning upwards at the end ; the stigmata are large and in their normal 
positions, one pair beneath, on the thorax, and eight pairs on the sides of 
the abdominal segments. 
The antenn are four-jointed, exceedingly minute and stout, and, as in 
Micromalthus, have the third joint lobed beneath, an apical spine, and oc- 
cupy similar positions on the anterior angles of the head; the maxillee also 
have the lobe divided into an upper and lower portion, although the sepa- 
ration is not very distinct, and appears under the lens as a corneous line, 
the spines upon the lobe are slender and not markedly different upon the 
two portions. The labrum and labinm are stout and thick, but do not pre- 
sent important structural differences from the same parts in Micromalthus. 
The mandibles are simple or slightly notched, the basal lobes not promi- 
nent, but finely ridged, and closing upon a triangular corneous piece which 
lies above the mentum. All the parts of the mouth in -Hylecwtus are 
smaller, stouter, and simpler in their structural details than the correspond- 
ing organs in Micromalthus, differences which perhaps have some relation 
to the harder material in which the former lives. Notwithstanding the 
striking difference in their external forms, the important structural analo- 
gies between the antennz and mouth parts, seem to indicate a relationship 
between these two larval forms. 
Explanation of Plate 15. 
Micromalthus debilis Lec., Imago, central figure. 
ib i “ «« Larva, enlarged twelve times. 
2,—Head and thoracic segments, lateral view ; much enlarged. 
3.—Terminal segments, showing the anal appendages, lateral view. 
4.—Head from above, very much enlarged. 
5.—Head from below, with mandibles omitted. 
6.—Right maxilla, seen from below. 
7.—Right antenna, from below. 
8.—Anal appendages, seen from below, very much enlarged. 
9.—Corneous triangular piece lying above the mentum, with the left 
mandible thrown back, seen from above ; the ridges upon the under sur- 
face of the mandible are indicated by dotted lines. 
Notrre—For the sake of distinctness, the appendages in fig. 3 are drawn 
too large in proportion to the segments. The proportions are more cor- 
rectly given in figs 1 and 8. 
