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Scarabaeoidea of Southern South America Links |
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Scarab Guide Links
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Classification |
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Brachysternus Guérin-Menéville
Brachysternus Guérin-Méneville 1831:3. |
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Brachysternus prasinus Guérin-Méneville.
Illustration by Dan Schmidt. |
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Type species. Brachysternus prasinus Guérin-Méneville, 1831 (by monotypy). |
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Description. Scarabaeidae, Rutelinae, Anoplognathini. Form (see habitus): Elongate oval,
sides subparallel, pygidium exposed beyond apices of elytra, apex of elytra broadly
rounded. Length from apex of clypeus to apex of elytra 16.0-25.0 mm; width at base
of elytra 7.0-12.0 mm. Dorsal color variable hues of green (metallic or opaque), castaneous
with metallic green shine, or bluish-green. Head: Disc of frons and clypeus in
lateral view nearly flat or weakly convex (more convex in males). Clypeal apex semicircular to rectangular with broadly rounded corners, weakly constricted at base or not;
margins and apex weakly or broadly reflexed (more reflexed in males). Frons and clypeus
variably punctate, some punctures setose; setae short to long, slender or thick, white to
orange, variable in density. Frontoclypeal suture complete, weakly bisinuate. Eye canthus
narrow, poorly developed, not cariniform. Interocular width 2.0-6.0 transverse eye diameters.
Region posterior to eye with or without thickened or scale-like setae. Mandibles with external margin rounded, with 1 inner tooth; molar region broad. Labrum vertically produced with respect to clypeus, with well-defined medial tooth, apex
broadly rounded. Maxilla with 6 poorly defined contiguous teeth in an arch,
mesal side forming an inner concavity; palpus 4-segmented, terminal segment (in dorsal
view) flattened, weakly or deeply sulcate, cylindrical or bean-shaped, 1.5 times longer
than segments 2-3 or subequal to segments 2-3. Mentum with well-defined
medial tooth, apex quadrate; palpus 3-segmented. Antenna 10-segmented with 3-segmented
club; club subequal to slightly longer than segments 1-7 combined (male) or
subequal to segments 2-7 combined (female). Pronotum: Form widest at middle, weakly
protuberant at mid-base, basolateral angle quadrate or feebly produced. Surface with
variably impressed, median, longitudinal groove and variably punctate, some punctures
setose; setae short to long, slender or thick, white to orange, variable in density. Marginal
bead complete laterally, incomplete basally (to slightly beyond posteriolateral angle or to middle of pronotum), lacking anteriorly. Scutellum: Shape parabolic, wider than long;
base declivous at elytral base. Variably punctate, some punctures setose; setae short to
long, slender or thick, white to orange, variable in density. Mesepimeron: Apex entirely
hidden by base of elytra in dorsal view. Elytron: Surface with 4-6 weakly impressed,
punctate striae; intervals variably punctate, some punctures setose; setae short to long,
slender or thick, white to orange, variable in density. Epipleuron rounded or flat, expanded
or not from metcoxa to sternite 2, region from base to sternite 2 with or without
bead; region from metacoxa to apex setose or not. Apex of elytron weakly rounded.
Sutural angle square or weakly rounded. Elytral sutural length 9.0-11.0 times length of
scutellum. Propygidium: Hidden or weakly exposed; posterior margin with a fringe of
setae; setae short to long, slender or thick, white to orangish. Supraspiracular ridge welldefined
or indicated by a line. Pygidium: Variably sculptured and setose, disc
of male convex, disc of female weakly convex or concave; setae short to long, slender
or thick, white to orangish, variably dense; margins beaded; apex rounded or quadrate.
Venter: Castaneous or testaceous in color, variably clothed with setae; setae short to
long, slender or thick, white to orangish, variably dense. Prosternal keel broadly triangular;
apex projecting anteriorly at about 458 with respect to ventral plane; apex produced
to about level of protrochanter, blunt. Mesometasternum with apex weakly produced
(quadrate or rounded) or not produced. Abdominal sternites 1-4 subequal in width in
male and female. Last sternite of male with subapex weakly sinuate, with fringe of setae,
apex quadrate. Last sternite of female moderately or deeply emarginated at middle. Legs: Profemur with apex weakly rounded and dilated. Protibia
with 3 teeth in apical half, basal tooth weakly removed from apical teeth, base with
weak protibial notch, apical spur lacking. Larger claw of male slightly thickened, subequal
in length to tarsomere 5, twice as thick as smaller claw, apex split or with a weak
nib at subapex or apex in frontal view. Larger claws of female not thickened (both claws
subequal in width), with or without ventral tooth. Unguitractor plate (all legs) laterally
flattened, exposed beyond tarsomere 5, apex with 2 long setae. Tarsomere 5 of male with or without ventromedial tooth or swelling. Pro- and mesotarsomere
4 with 2 apical spines, spines recurved at apex. Mesotibia with sides
subparallel, apical 1/5 weakly divergent, external edge with 1-2 carinae; apex with 2
inner spurs, 10-14 spinulae, spinulae short to moderately long. Metacoxa with externolateral
apex membranous, square or weakly acute. Metatrochanter with apex weakly
produced beyond posterior border of femur. Metatibia with inner edge
straight or weakly bowed inwardly, outer edge straight or weakly bowed outwardly, with
1-2 carinae, apical 1/5 divergent (more so in females; or not; apex with 2
inner spurs, 14-26 spinulae, spinulae short to moderately long. Hind wing:
Precosta with poorly developed hooks present on ScA; setae present either side of RA314.
Vein AA112 about 1/4 length of AA314. AP314 with bulbous, enlarged base. Male genitalia:
Parameres and ventral plates symmetrical. Female gonocoxites: Simple,
symmetrical. |
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Diagnosis. In the Brachysternina, Brachysternus is separated from Hylamorpha
by the following characters: 1) unguitractor plate with 2 setae (multisetose
in Hylamorpha), 2) protarsomere 4 with 2 recurved spines (not recurved
in Hylamorpha), 3) propygidium with supraspiracular ridge (lacking in
Hylamorpha), 4) last sternite of the female weakly or deeply emarginated at
the middle (rounded in Hylamorpha). Brachysternus is separated from Aulacopalpus based on the following characters: 1) last sternite of the female weakly
or deeply emarginated at the middle (rounded in Aulacopalpus), 2) male
parameres with well developed ventral and lateral sclerites (poorly developed
in Aulacopalpus). |
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Distribution. Southwestern South America. |
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Natural History. Species of Brachysternus are known to occur from sea
level to 2,000 m elevation within southwestern South America. Their distribution
corresponds to the distribution of Nothofagus species on which they feed. Adults are attracted to lights at night. Larvae are not known but probably
feed on decaying wood or vegetation. |
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Comments. Some species in the genus Brachysternus were previously
placed in the brachysternine genera Aulacopalpus, Sulcipalpus Harold (=Aulacopalpus),
and Tribostethes Curtis (=Aulacopalpus). The following species
were originally described in the genus Brachysternus but were subsequently
transferred to other genera: Brachysternus castaneus Laporte (now Aulacopalpus
castaneus) and Brachysternus lamprimoides White (now Epichrysus
lamprimoides [subtribe Anoplognathina]). |
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Excerpt from:
Jameson, M. L. and A. B. T. Smith. 2002. Revision of the South American genus Brachysternus Guérin-Ménville (Coleoptera: Ruteliinae: Anoplognathini: Brachysternina). Coleopterists Bulletin 56: 321-366. |
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