- A study of the immature stages of the subfamily Troginae in
North America was conducted from the spring of 1963 through the
spring of 1965, Larvae of Trox and Omorgus were easily reared in
the laboratory, but all attempts to rear the larvae of Glaresis were
The suberosus group, one of the five groups of species within
the genus Trox in North America as recognized by Vaurie (1955), is
given generic status. The 17 species of the suberosus group are
placed in the genus Omorgus which was originally proposed by
Erichson (1847) with Trox suberosus later designated as the type.
The placement of these 17 species in Omorgus is done on the basis of
the larval morphology and recent work on the morphology and cytogenetics
of the adults. A table listing 17 characters by which the genus Trox may be distinguished from the genus Omorgus is presented.
The other four groups of species in North America, as
recognized by Vaurie (1955), are retained in the genus Trox.
The adults of 22 species of Trox and Omorgus were collected
during the summers of 1963, 1964, and 1965, in the states of Oregon,
Arizona, New Mexico, and Texas. Cultures of these beetles were
established in the laboratory and 595 larvae were reared for the
systematic studies of the immature stages. Additional material was
borrowed from the U. S. National Museum and Dr. P. O. Ritcher,
and the larvae of two species were used for the descriptions.
Generic descriptions of the larvae of Trox and Omorgus are given
along with brief descriptions of 24 of the 42 species of these genera
known to occur in North America. The larvae of the following
species are described: T. scaber (L.), T. aequalis Say, T. fascifer
LeConte, T. atrox LeConte, T. spinulosus dentibius Robinson, T.
foveicollis Harold, T. frontera Vaurie, T. sonorae LeConte, T.
robinsoni Vaurie, T. tuberculatus (De Geer), T. plicatus Robinson,
T. sordidus LeConte, T. variolatus Melsheimer, T. unistriatus
Beauvois, O. suberosus (Fabricius), O. rubricans (Robinson), O.
carinatus (Loomis), O. monachus (Herbst), O. fuliginosus (Robinson),
O. asper LeConte, O. punctatus (Germar), O. inflatus (Loomis), O.
texanus LeConte, O. scutellaris (Say).
The general life history of Trox scaber (L.) as it occurs in the laboratory is described and notes on other species are included.
A section on the general biology of Trox and Omorgus is given. The
method whereby the immature stages of Trox and Omorgus were
reared is described. Pertinent morphological characters of the immature
stages are presented in 59 figures, and the literature of the
immature stages reviewed on a worldwide basis.
A key to the third stage larvae is given, but larvae of several
closely related species were inseparable and are keyed out in the
same couplet. Structures of taxonomic importance include the epipharynx,
hypopharynx, antennae, head capsule setation and topography,
maxillae, spiracles, and setal and spinule patterns on the
thoracic and abdominal lobes and legs.
A simplified terminology is utilized for reference to the
lobes of the abdominal and thoracic regions. The terms subtorma,
subapotorma, and fused phobal mass are proposed to facilitate the
description of the larval hypopharynx and epipharynx.
A synoptic collection of the larvae utilized in this study has
been deposited in the collection of the U. S. National Museum,