144 ENTOMOLOGICAL SOCIETY 
The larvae of thirteen out of nineteen known species of Den- 
droctonus are included in the table of characters. According 
to these, the species fall naturally into two primary divisions 
and four sub-divisions, characterized as follows: In the first 
division, including nine species, the 8th and 9th abdominal 
segments are without dorsal plates, while in the second division, 
including four species, they have distinct plates. The first 
division is further separated by the presence or absence of 
an elevated ridge near the anterior margin of the epistoma, 
but the most important character to designate the species is 
the absence or presence of a frontal elevation and the form 
and general character of the latter. 
In the first sub-division of the second division the dorsal 
plates of the 8th and 9th abdominal segments are unarmed, 
while in the second subdivision they are armed with prominent 
teeth. The more important characters separating the species 
are found in the frontal area, the clypeus and labrum, all of 
which are readily observed and recognized in dried specimens, 
when pinned or mounted on card points. Indeed, if the larvae 
are properly treated, even the softer parts are nicely pre- 
served in the dried specimens. 
Another character which is of value in separating some of 
the species is the presence or absence of foot scars on the 
ventral lobes of the thoracic segments. 
In the literature on coleopterous larvae the mentum, maxillae, 
and mandibles have received special attention, while the 
labrum and the taxonomic importance of its structure and 
variable parts, has not received the attention it seems to 
deserve. Packard, in his Text Book of Entomology, appears 
to be the first to call attention to the importance of the epi- 
pharynx, especially in coleopterous larvae, and expresses surprise 
that this structure has been overlooked by so many leading 
entomologists. Considerable information has been published 
concerning the labrum of insects, especially in its relation to 
the segments of the head, but as in the general subject of 
head segmentation, there is a wide range of opinions and 
conclusions. 
In the labrum of the Scoly tid larvae, as in that of representa- 
tives of a number of other families of Coleoptera that I have 
examined, there is a pair of chitinous ventral structures which 
are of especial interest (Plate IV, Fig. 8) . They are attached to, 
and sometimes extend through, the dorsal exoskeleton of the 
labrum. In some species they appear on the dorsal surface as 
black or dark tubercles, which were noted by Heeger in 1854 m 
certain curculionid larvae, and briefly referred to and figured in 
his natural historv of insects. 
