Brychius pacificus Carr
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https://doi.org/ 10.1649/0010 |
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persistent identifier |
https://treatment.plazi.org/id/03C0651D-3410-FFB1-9DC3-FEDD57265E3B |
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Valdenar |
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Brychius pacificus Carr |
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Carr, F.S., 1928: 23 (original description)
( Figures 1c, 1f View Fig ; 2c View Fig ; 3c View Fig ; 4c View Fig ; 5c View Fig ; 6c View Fig ; 7c View Fig ; 8c View Fig ; 9c View Fig ; 10c View Fig ; 11c View Fig ; 12c View Fig ; 13c View Fig ; 14c View Fig ).
TYPE MATERIAL: Brychius pacificus : Holotype: Male – ‘‘Hmbldt Co/Cal’’, Coll’. JD/Sherman/Jr. 1926’’, ‘‘Type No./41755/ U.S. N.M.’’ [red], ‘‘ Brychius / pacificus/Carr/Type [written sideways]/ex coll. F.S. Carr’’ [white label w/black trim] ( USNM).
Diagnosis
The adults of this species can be distinguished from the other species by: prosternal process constricted at level of procoxae, gradually widening to apex making the anterior lobe distinctly wedge-shaped; last abdominal segment with blunt point. Males can be distinguished from those of the other species by having the median lobe elongate and slender, with the apex slightly pointed and the hood lobe truncated, with a deep, distinct channel separating it from the median lobe. Left paramere with a larger, rough surface at apex.
The larva is unknown.
Description
Adults
Body. – Total body length 3.3–3.7 mm; maximum body width 1.71–1.93 mm. Elongate, slender. Color testaceous to dark brown. Characteristic elytral maculation.
Head. – Surface with evenly spaced, larger punctures. Head and antennae yellow to testaceous. Light infuscation on base of head on some specimens.
Mouthparts. – Labroclypeus similar to that of B. hornii and B. hungerfordi .
Mandibles asymmetrical; right mandible ( Fig. 1c View Fig ) with one notched apical tooth; retinaculum with mesal comb or brush of setae not extending past retinaculum concavity. Truncated projection smooth. Left mandible ( Fig. 1f View Fig ) with one apical tooth; retinaculum with brush of setae. Maxilla ( Fig. 2c View Fig ) with lacinia having spines along inner margin and elongate two-segmented galea; apical segment of galea tapered towards apex, smooth. Labium ( Fig. 3c View Fig ) with very wide, rounded base, ligula with lateral setae, two anterolateral small projections; penultimate segment of labial palp without lateral sinuation.
Pronotum. – No transverse depression in lateral view at base between two plicae; pronotum margined laterally. Color testaceous to brown; anterior margin usually infuscate; two piceous to brown spots on posterior margins; piceous band on posterior margin. Surface covered with punctures, which are larger and coarser in piceous areas. Lateral edges margined with fine serrations.
Elytron ( Fig. 4c View Fig ). – Elongate, tapering from sixth abdominal segment to apex. Posterolateral margins finely serrate. Color testaceous to brown; five inner striae of punctures on each elytron, pigmented; pigmentation abbreviated apically but hardly basally, spreads out from punctures. Piceous humeral spot present covering sixth and seventh striae and intervals. At outer edges, another spot stretching over sixth, seventh, eighth and ninth striae and intervals. At three quarter length, another spot covering seventh and eighth striae and intervals. In some specimens, there is a spot in the middle connecting the sutural stripe with the first and second striae. Apical margin of elytra rounded, apices denticulate.
Hind Wing ( Fig. 5c View Fig ). – R3 without crossvein to C. Ct forming semi-circular open cell. Rr without horizontal vein; AP and AA present.
Ventral surface. – Prosternal process with poorly developed lateral margins becoming very faint or disappearing anteriorly; constricted at level of procoxae, gradually widening anteriorly, making anterior lobe appear distinctly wedgeshaped ( Fig. 6c View Fig ); reddish-yellow; surface coarsely punctate with micropunctures in interspaces. Metasternal process not depressed posteriorly; margined on lateral edges, thicker margining in anterior portion, margins continued in line with those of prosternal process; punctures same as on prosternal process with micropunctures in interspaces. Metasternum with large, sparse punctures. First two visible abdominal sternites heavily pigmented with piceous, coarse punctures; last two segments more finely punctate. The last segment almost obtusely angulate with noticeable slit medially from apex, more than half length of segment; apex with short point.
Legs. – Prothoracic leg ( Fig. 12c View Fig ). Coxa square-shaped. Trochanter small, rectangular, length of tarsomere 1. Femur with dorsal row of spines, long dorsal natatory setae. Tibia slightly shorter than femur, dorsally and ventrally with stout spines, apical end with short dorsal natatory setae and two stout ventral spines.
Tarsus with five segments; all tarsomeres with long natatory setae; tarsomere 1 equal to length of tarsomere 4; tarsomere 2 slightly longer than tarsomere 3; tarsomere 4 with long ventral spines; tarsomere 5 longest tarsal segment with large ventral spines. Pretarsus of two long claws.
Mesothoracic leg ( Fig. 13c View Fig ). Coxa rounded. Trochanter small, rectangular.
Femur with dorsal row of spines; few natatory setae dorso-basally, cluster of natatory setae dorso-apically. Tibia slightly shorter than femur, with dorsal and ventral rows of stout spines, long dorso-apical natatory setae, two ventro-apical stout spines. Tarsus with five segments; tarsomere 1 with natatory setae; tarsomere 2 shortest segment; tarsomere 3 and 4 equal in length; tarsomere 5 longest segment with stout row of ventral spines. Pretarsus of two long claws.
Metathoracic leg ( Fig. 14c View Fig ). Femur with basal end bulbous, remainder long and slender, dorsal and ventral spines. Tibia slender, longest segment, with row of dorsal and ventral spines, longer spines at apical end. Tarsus with five segments; long natatory setae absent; tarsomere 1 subequal to length of tarsomeres 2 and 3 combined, with basal spines; tarsomere 2, 3, and 4 subequal with basal spines; tarsomere 5 with row of ventral spines. Pretarsus consisting of two long claws.
Female sexual characters. – Tergite VIII ( Fig. 7c View Fig ) rounded, wide basally.
Gonocoxae ( Fig. 8c View Fig ) with large space separating two apical lobes; apices of lobes with long, stout spines.
Male sexual characters. – Aedeagus ( Fig. 11c View Fig ) with median lobe having a distinct curvature, apex elongate, slender, with a slightly pointed tip; hood lobe distinctly square, a deep distinct channel separating it from the median lobe. Left
paramere ( Fig. 9c View Fig ) with larger platform surface at apex. Right paramere ( Fig. 10c View Fig ) with truncated apex.
Distribution
( Figures 30–32 View Fig View Fig View Fig ).
This species is found on the west coast of Oregon and California.
384 Quantitative Analysis of Structure
A morphometric analysis was undertaken with the intention of providing quantitative length and width measurements of body structures to discriminate adults of Nearctic species of Brychius . Initial analysis using basic graphing was first performed to determine if any of the characters were uninformative. Principal Component Analysis (PCA) using a covariance matrix was performed to identify the most informative characters and eliminate autocorrelated characters. Multiple Discriminant Analysis (MDA) was then performed to test species discrimination and to observe variation within the species. Discriminant analysis was carried out using raw and ratio data.
Males and females were analyzed separately, as females are larger, on average, than males in all species of Brychius . Populations of B. hornii from Creston, BC; Fort McMurray, AB; Cypress Hills, AB; and Cowan, MB were analyzed separately. These populations are geographically isolated and it was thought they could show significant structural differences.
Males
In the analysis, specimens of B. hungerfordi were the only ones to separate completely from specimens of the other species. This occurred on the first axis with the characters pronotal width (Pr1) and pronotal length (Pr2) ( Fig. 33a View Fig ). Even though specimens of B. pacificus and B. hornii completely overlapped in size, 95% confidence ellipses placed around the centroids produced noticeable population groups within B. hornii . The population of B. hornii from Cowan, MB was the most similar to those of B. hungerfordi and the least similar to those of B. pacificus . The population of B. hornii from Cypress Hills, AB was the least similar to those of B. hungerfordi . The population of B. hornii from Fort McMurray, AB 386 completely enclosed the centroid radius of B. pacificus and the population of B. hornii from Creston, BC.
The character most closely associated with the second axis was tarsomere 1 length (Ta1); however, this only slightly separated specimens of B. pacificus from specimens of the other species.
Females
Separation of females of Brychius spp. was less definitive on the first axis than for male specimens; however, the trends were the same ( Fig. 33b View Fig ). Similar to the analysis of males, specimens of B. hungerfordi were seen to separate distinctly from specimens of the other species, while specimens of B. pacificus and B. hornii completely overlapped in size. Within B. hornii , the population from Cowan, MB was the most similar to those of B. hungerfordi and the least similar to those of B. pacificus . The population of B. hornii from Cypress Hills, AB was more similar to the remaining B. hornii populations in the female analysis than in the male analysis. The population of B. hornii from Fort McMurray, AB was closer to B. pacificus than it was to the population of B. hornii from Creston, BC.
In the analysis of females, the second axis was more effective than that of the analysis of males for distinguishing populations of B. pacificus and the population of B. hornii from Creston, BC using the length of the metasternum (M2). However, there was still complete overlap among specimens of the two species.
Overall Trends
The populations of B. hornii from Fort McMurray, AB and Cypress Hills, AB had the greatest variation out of the six groups analyzed. In both sexes, specimens of B. hornii overlapped greatly with specimens of B. pacificus . Specimens of B. hungerfordi were the only ones to separate completely from specimens of the other species. This is not surprising as B. hungerfordi is quite isolated from the other species. The character that was best to discriminate this species from the others 388 was the width of the pronotum. However, because the width differed from specimens of B. hornii by only 0.02 mm ( Fig. 34 View Fig ), it is impractical to use this character for identification purposes. The overall size of specimens of B. hungerfordi was also variable, as with the other species. This is congruent to the findings of Spangler (1954, p. 116) who stated ‘‘the size of B. hungerfordi from Maple River, Emmet Co. Michigan varies considerably within each sex. The smallest specimen in the series is a male, 3.70 mm in length and 1.90 mm in width, while the largest is a female, 4.35 mm in length and 2.25 mm in width’’. The addition of selected ratios can sometimes reduce the error of overlapping discriminate groups through compensating for variation of body size among a species; however, this did not affect the results of my analysis when added.
Phylogeny
A structural matrix including 20 adult characters was produced ( Table 2). In the PAUP analysis, the exhaustive search yielded one tree ( Fig. 35 View Fig ) of length 33, with a Consistency Index of 0.82, and a Retention Index of 0.71. Generally, nodes had low bootstrap support; therefore, interpretation of the tree should be regarded with caution .
390 In the cladogram, B. pacificus is basal to all other species of Brychius . Brychius hornii and B. hungerfordi are sister species and B. elevatus and B. glabratus are sister species. The monophyly of B. hornii and B. hungerfordi is indicated by four characters: 1) prosternal process with anterior lateral margins parallel (C9); 2) lateral view of ventral margin of metasternum impressed (C10); 3) humeral region of elytra angled (C14); and 4) apical sternite of abdomen with a long, sharp point (C19). The monophyly of B. elevatus and B. glabratus is indicated by one character: metasternal process with a large anterior median impression (C11). The monophyly of species of Brychius excluding B. pacificus is indicated by four characters: 1) mandible with two apical teeth (C1); 2) pronotum in lateral view with a basal transverse impression (C6); 3) anterior lateral margins of pronotal process with thick margins (C8); and 4) apex of elytra acute.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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