Monochamus scutellatus

Taxonomic history

Cerambyx scutellatus Say, 1824: 289

Diagnosis - adult

Length: 13–35mm.
Elytral length:width ratio: length > 2x width.
Face: shape wide rectangle; genagena:
the part of the cranium on each side below the eye
length longer than lower eye lobelobe:
a rounded projection or protuberence
or subequal to lower eye lobelobe:
a rounded projection or protuberence
.
Pronotum: dense setaeseta:
a sclerotized hair-like projection of the cuticle
on dorsum of lateral spines absent; maculaemacula:
a spot or mark
on pronotal disk: absent; posteromedial tubercletubercle:
a small knoblike or rounded protuberance
absent; lateral erect setae:seta:
a sclerotized hair-like projection of the cuticle
:: present posterior and anterior to spinespine:
a protuberance with an acute (sharp) distal end
or only present posterior to spinespine:
a protuberance with an acute (sharp) distal end
.
Scutellum: dense and complete pubescence or pubescence broken at least partially along midline.
Elytra: Elytra:Elytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
:l integument color black; Elytra:Elytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
:l maculae:macula:
a spot or mark
:: sparse ash-like pubescence, absent, rarely many small circular spots; Elytra:Elytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
:l sutural apexapex:
end of any structure distad to the base
rounded; elevation in basal third followed by impression present or absent; basal granulation dense and smooth; middle to apical punctationpunctation:
pits or depression of variable size in cuticle
fine.
Antennal length (female): 2–3.5 segments beyond Elytra:Elytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
:l apexapex:
end of any structure distad to the base
.
Aedeagusaedeagus:
in male beetles, the penis
paramereparamere:
A pair of finger-like structures that are located where the male genitalia exits the abdomen.
mediobasal tooth present; apical tip (ventral view) slightly rounded; scleritesclerite:
any hardened plate of the body wall bounded by membrane or sutures; sometimes found floating in the internal sac of male genitalia
in internal sac: scleritesclerite:
any hardened plate of the body wall bounded by membrane or sutures; sometimes found floating in the internal sac of male genitalia
absent.

Male. Form moderate-sized to large; integument black, shining, often with a brassy caste, appendages often partially reddish, pubescence sparse to moderately dense, short, brownish, appressed. Head with front convex, finely to coarsely, confluently punctatepunctate:
set with fine, impressed points or punctures appearing as pin-pricks
, usually sparsely clothed with fine recumbent pubescence; genaegena:
the part of the cranium on each side below the eye
longer than lower eye lobelobe:
a rounded projection or protuberence
, parallel to slightly convergent antennaeantenna:
in larval and adult insects, paired segmented appendages, borne one on each side of the head, functioning as sense organs and bearing a large number of sensilla
extending five or six segments beyond elytraelytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
, usually twice the length of the body, segments finely, very densely asperate, nonpubescent, segments from third or fourth with apical sensory areas. Pronotumpronotum:
the upper and dorsal part of the prothorax
about as broad as long, lateral tubercles strongly produced, apicesapex:
end of any structure distad to the base
blunt: apical and basal transversetransverse:
broader than long
impressions shallow, plicate; disk irregularly, transversely punctatepunctate:
set with fine, impressed points or punctures appearing as pin-pricks
at middle, center often longitudinally impressed; pubescence sparse, short, fine; prosternum glabrousglabrous:
smooth, devoid of pubescence; devoid of any sculpturing
to moderately pubescentpubescent:
downy; clothed with soft, short, fine, loosely set hair
: meso- and metasternum sparsely to densely clothed with long suberect hairs and often small patches of white appressed pubescence. ElytraElytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
a little more than twice as long as broad; punctures coarse, transversetransverse:
broader than long
, rugoserugose:
wrinkled
appearing, becoming finer toward apexapex:
end of any structure distad to the base
: pubescence very fine, brownish, sparse to moderately dense, often with small patches of white appressed pubescence at basal one-third; apicesapex:
end of any structure distad to the base
rounded. Scutellumscutellum:
a small sclerite located directly posterior to the pronotum, bordered laterally by the elytra
apically rounded, densely white pubescentpubescent:
downy; clothed with soft, short, fine, loosely set hair
, usually with a glabrousglabrous:
smooth, devoid of pubescence; devoid of any sculpturing
median line. Legs finely gray pubescentpubescent:
downy; clothed with soft, short, fine, loosely set hair
. Abdomen sparsely to moderately densely pubescentpubescent:
downy; clothed with soft, short, fine, loosely set hair
: last sternite rounded to subtruncatesubtruncate:
not quite cut off squarely at the tip
at apexapex:
end of any structure distad to the base
. Length, 13–35 mm.

Female. Form more robust. AntennaeAntenna:
in larval and adult insects, paired segmented appendages, borne one on each side of the head, functioning as sense organs and bearing a large number of sensilla
extending two or three segments beyond elytraelytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
, segments apically broadly white annulateannulate:
surrounded by a ring of a different color
, not asperate. ElytraElytron:
the leathery forewing of beetles, serving as a covering for the hind wings, commonly meeting opposite elytron in a straight line down the middle of the dorsum in repose
usually with scattered small patches of white appressed pubescence. Abdomen with last sternite truncatetruncate:
cut off squarely at the tip
to shallowly emarginateemarginate:
notched at the margin
at apexapex:
end of any structure distad to the base
, densely tufted. Length, 14–30 mm. (Chemsak 1984)

Similar species

M. sutor, M. sartor, M. impluviatus

Differential diagnosis

The black integument with rounded sutural apexapex:
end of any structure distad to the base
is distinctive among North American species. When comparing with similar Eurasian species, M. scutellatus has ashier-looking pubescence with minimal spots, no pubescentpubescent:
downy; clothed with soft, short, fine, loosely set hair
dots on pronotumpronotum:
the upper and dorsal part of the prothorax
disc, and no floating scleritesclerite:
any hardened plate of the body wall bounded by membrane or sutures; sometimes found floating in the internal sac of male genitalia
in the male genital internal sac.

Distribution

North America

Recorded host plants

Pinus, Abies, Larix, Picea, Pseudotsuga, Tsuga (Bousquet et al. 2017)

Remarks

Recent molecular work has shown that the subspecies within M. scutellatus are not supported and others have published similar notes (Bousquet et al. 2017).

Synonyms

Monochamus resutor Kirby, 1837: 167

Monohammus oregonensis LeConte, 1873: 231

Monochamus monticola Casey, 1913: 293