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Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region
CJAI 05, February 19, 2008
doi: 10.3752/cjai.2008.05

Matthias Buck, Stephen A. Marshall, and David K.B. Cheung

Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1

 

Note: due to the difficulties in separating these two genera, the species of Parancistrocerus and Stenodynerus are treated in a single key.

Parancistrocerus Bequaert

Parancistrocerus is primarily a New World and Oriental genus with one species in the Palaearctic. The North American fauna consists of 25 species (updated from Krombein 1979; see taxonomic note under P. fulvipes), nine of which occur in the northeast. Five species are recorded from eastern Canada.

References. – Bohart, 1952 (key to Nearctic species), 1948b (key to Florida species of Parancistrocerus and Stenodynerus).

Stenodynerus de Saussure

This genus is widely distributed in the New World, as well as the Palaearctic and Oriental regions. With 48 described species it is the largest vespid genus in America north of Mexico (Krombein 1979). The northeastern fauna is comprised of 11 species, five of which occur in Canada. Up to the present only partial keys to the eastern Nearctic fauna existed, which rendered the identification of northeastern material extremely difficult. The present key in conjunction with Bohart’s (1948b) key to red-marked southeastern species covers almost the entire eastern fauna (exception: S. propinquus, which occurs from NC and AL westward, see diagnosis under S. fundatiformis; note that the red-marked Floridian forms of S. blepharus and S. krombeini are not included in Bohart’s key and that ‘S. ammonia’ sensu Bohart, nec (de Saussure) = S. histrionalis rufustus).

References. – Bohart, 1953 (key to S. blepharus and related species), 1948b (key to Florida species of Stenodynerus and Parancistrocerus), 1944 (review of S. propinquus-group, key), 1943 (review of S. anormis-group, key).

7. Key to northeastern Nearctic species of Parancistrocerus and Stenodynerus

1. Humeral carina short but well-developed, continuing pronotal carina posteriorly (Fig. 7.3). Omaulus strong and nearly straight ventrally, not or very slightly curving posteriorly (Fig. 7.1). Pronotal hind margin between tegulae completely bordered with yellow (Fig. 7.3, sometimes obscure posteriorly). Male: mid femur with low anteroventral swelling just before middle (Fig. 7.4). [Flagellomere VIII of male with deep apical emargination on inner side. Pronotal carina strong medially (Fig. 7.3). Tergum 3 with complete apical fascia (Fig. 7.57).] (U.S.: NY and MN southward) S. fundatiformis
(Robertson)
- Humeral carina absent. Omaulus in most species distinctly curved posteriorly and becoming weak ventrally (Fig. 7.1). Pronotal hind margin black or brownish. Male: mid femur simple or variously modified but not as above 2
2. Sternum 2 in lateral view bluntly angled behind basal groove (Fig. 7.5), without median longitudinal crease. [Interocellar area without tubercles. Pronotal carina weakly defined. Summit of tergum 1 without transverse carina. Terga 1 and 2 lacking discal yellow spots; metasomal terga almost always entirely black beyond segment 2 (Fig. 7.5). Male: flagellum yellow beneath; mid femur without anteroventral depression near base.] P. perennis
(de Saussure)
- Sternum 2 in lateral view evenly convex behind basal groove (e.g., Fig. 7.6), with median longitudinal crease 3
3. Mid ocellus bordered posteriorly by low and eyelid-like, sometimes conspicuous, swelling (Fig. 7.7, better developed in male than in female), the swelling clearly projecting above level of ocellus in anterior view and usually separated from it by a fine crease 4
-
Area immediately behind mid ocellus flat, not projecting above level of ocellus in anteroventral view; mid ocellus not bordered by fine crease posteriorly (e.g., Fig. 7.8)
7
4. Tergum 1 near summit with scattered long hairs that are several times longer than the general pubescence (similar to Fig. 7.6). Pronotal carina strongly developed, including medially (as in Fig. 7.3). Acarinarium present (cf. Key 2, couplet 4) (U.S.: NY and MI southward) P. bicornis
(Robertson)
- Tergum 1 near summit with uniform short pubescence. Pronotal carina interrupted or weak medially. Acarinarium absent (cf. Key 2, couplet 4) 5
5. Vertex with a pair of (sometimes poorly developed) impunctate swellings near summit of eye slightly behind level of hind ocelli (Fig. 7.9). Tergum 2 with pits in basal groove shallow or obsolete medially (Fig. 7.14). Pronotum with punctures well separated (Fig. 7.9; on average by one mid ocellar diameter, in some spots by distinctly more). Size larger, fore wing length 5.5–7.0 (male), 7.0–8.0 mm (female). Male: flagellomere XI slender, its width < 0.25x that of flagellomere IX (Fig. 7.10); flagellum black to orange-yellow ventrally; base of fore femur with scattered longish hairs ventrally (length ≤ 0.4x mid ocellar diameter) among extremely short hairs (Fig. 7.12). (U.S.: MI and MA southward) S. pulvinatus
Bohart
- Vertex without impunctate swellings near summit of eye. Tergum 2 with pits in basal groove deep, including medially (as in Fig. 7.16). Pronotum with punctures denser, usually separated by less than one mid ocellar diameter (Figs 7.19–20). Size smaller, fore wing length 4.8–5.5 (male), 5.5–6.5 mm (female). Male: flagellomere XI broad, its width ca. 0.35x that of flagellomere IX (Fig. 7.11); flagellum extensively yellow ventrally; base of fore femur with extremely short uniform hairs ventrally, without longer hairs (Fig. 7.13) 6
6. Pronotal carina almost always complete medially (similar to Fig. 2.12). Parategula narrowed near middle, somewhat to strongly incurved along oblique posteromedial margin, and hooked or pointed toward apex (Fig. 7.19). Tergum 1 with or without small round discal spots, if present the spots usually connected to apical fascia (Fig. 7.59). Sternum 2 without yellow discal spots. Clypeus with coarse punctures (Fig. 7.17). Male: flagellomere IX with sharply delimited shining area opposite flagellomere XI (Fig. 7.11); interantennal spot round, not extending ventrally beyond interantennal prominence (Fig. 7.17) S. blepharus
Bohart
-
Pronotal carina briefly interrupted medially by smooth or punctate area. Parategula wide throughout, with convex or at least straight posteromedial margin, usually broadly rounded at apex (Fig. 7.20). Tergum 1 with elongate oblique spots laterally, usually connected to apical fascia; sternum 2 often with yellow discal spots, especially in male (Fig. 7.60). Clypeus with fine punctures (Fig. 7.18, coarser in female). Male: flagellomere IX dull throughout; interantennal spot elongate, extending to base of clypeus ventrally (Fig. 7.18) (U.S.: NY, MI and MN southward)
S. oculeus
(Robertson)
7.
Clypeal apex straight to slightly convex (Fig. 7.21). Male: mid femur laterally compressed in basal half, sometimes conspicuously distorted (Figs 7.23–24); flagellomere XI very broad with shining apex that fits into deep apical emargination of flagellomere VIII (Fig. 7.22). [Acarinarium absent]
8
- Clypeal apex at least slightly emarginate (e.g., Figs 7.27, 7.31, 7.33–34, 7.39; rarely almost straight). Male: mid femur simple or with more or less distinct anteroventral depression in basal third (Fig. 7.36); flagellomere XI narrow to slightly broadened, dull throughout; apex of flagellomere VIII at most shallowly emarginate (depth of emargination < 0.5x mid ocellar diameter) 9
8. Summit of tergum 1 without transverse carina; punctures scattered. Pronotal carina well defined but low medially (similar to Fig. 2.12). Terga with apical fasciae becoming paler on caudal segments; tergum 1 with yellow discal spots (often connected to apical fascia) (Fig. 7.61). Male mid femur strongly distorted, with deep oblique anterior depression in basal half, dorsoventrally flattened in distal half (Fig. 7.24) S. anormis
(Say)
- Summit of tergum 1 with an irregular transverse carina formed by enlarged confluent punctures followed by smooth area (Fig. 7.25). Pronotal carina rounded over medially. Terga with apical fasciae bright yellow; tergum 1 without discal spots (spots present in specimens from southern U.S.) (Fig. 7.62). Male mid femur with moderate anterior depression in basal half, not flattened distally (Fig. 7.23) S. ammonia
(de Saussure)
9. Horizontal part of tergum 1 with sparse to abundant long hairs near summit (length greater than mid ocellar diameter; Fig. 7.6). [Terga 1 and 2 with yellow discal spots, on former often connected to apical fascia (Fig. 7.6). Acarinarium present.] 10
- Tergum 1 with shorter hairs (length less than mid ocellar diameter) 11
10. Summit of tergum 1 with irregular transverse carina formed by anterior margin of confluent punctures followed by smooth area (Fig. 7.26). Pronotal carina interrupted medially. Interocellar area not tuberculate, with shallow median impression. Tergum 3 with apical fascia usually interrupted medially. Male: ocelli large, mid ocellus usually separated from hind ocelli by its own diameter or less (Fig. 7.27) (U.S.: NJ southward) P. salcularis
(de Saussure)
- Summit of tergum 1 without transverse carina. Pronotal carina entire (Fig. 2.12). Each hind ocellus bordered medially by low tubercle; the tubercle in male always, in female usually projecting above level of ocellus in lateral view (Fig. 7.28). Tergum 3 with complete apical fascia (Fig. 7.6). Male: ocelli of usual size, mid ocellus separated from hind ocelli by at least 1.2x its own diameter P. leionotus
(Viereck)
11. Tergum 2 with subbasal median depression (sometimes hidden under tergum 1) forming entrance to acarinarium (Fig. 7.29, shallower in male). Male: clypeus with sharp apicolateral teeth bordering deep median emargination (depth greater than mid ocellar diameter; Fig. 7.8). [Summit of tergum 1 without transverse carina. Tergum 1 and almost always tergum 2 with discal spots, on former often connected to apical fascia; tergum 3 with complete apical fascia (Fig. 7.51). Male mid femur slightly depressed anteroventrally near base (as in Fig. 7.36). Tegula and usually mid and hind tibia without yellow, uniformly amber-reddish.] P. vagus
(de Saussure)
- Tergum 2 without subbasal median depression (e.g., Figs 7.14–16, 7.40). Male: clypeus with shallow apicomedial emargination (e.g., Fig. 7.31; its depth less than mid ocellar diameter) 12
12 Tergum 1 with posterior, horizontal part convex in lateral view (Fig. 7.30). [Pronotal carina complete. Summit of tergum 1 with conspicuous transverse carina formed by row of confluent coarse punctures followed by posteriorly convex smooth area (similar to Fig. 7.26). Tergum 1 with yellow discal spots (usually connected to apical fascia); tergum 2 without discal spots; the following terga without apical fasciae except in some males (Fig. 7.30).] (U.S.: MI southward) P. fulvipes
(de Saussure)
- Tergum 1 with posterior, horizontal part straight in lateral view (Figs 7.54, 7.56, 7.63–64, 7.65–66, 7.67–68). Summit of tergum 1 usually without transverse carina but if present (S. histrionalis and S. lineatifrons; Figs 7.65–66) the carina less conspicuous and following smooth area not convex. If tergum 1 with yellow spots then tergum 2 also spotted 13
13. Metasoma without pale markings beyond segment 2 (Figs 7.53, 7.63–64, 7.65–66) 14
- Metasoma with yellow or ivory apical fasciae on one or more terga beyond segment 2 (Figs 7.54–56, 7.67–68) 17
  Note: S. histrionalis keys both ways.  
14. Body with pale markings ivory to pale yellow. Eye emargination without pale spot (Fig. 7.31). Tergum 1 with small punctures and no carina at summit (Figs 7.63–64). Male: flagellomere XI unusually small and slender, not extending to base of flagellomere IX (Fig. 7.35). Female: legs almost completely black except anterior surface of fore tibia and apex of fore femur. [Male: mid femur without anteroventral depression near base; flagellum black beneath except sometimes apical flagellomeres.] (Canada) S. lucidus
(Rohwer)
- Body with pale markings bright yellow to ferruginous; propodeum and tergum 1 often largely ferruginous (Figs 7.53, 7.65). Eye emargination with yellow or reddish spot (Figs 7.33–34). Summit of tergum 1 with an irregular transverse carina formed by coarse, confluent punctures (Figs 7.53, 7.65–66). Male: flagellomere XI larger, extending to base of flagellomere IX. Female: legs largely reddish or yellow to orange-yellow with brown or black (eastern U.S.) 15
15. Tergum 1 with an acarinarium under its apical margin; tergum 2 with basal transverse groove smooth (as in Fig. 7.40). Tergum 2 without pair of spots and sometimes also without apical fascia (Fig. 7.53). Male mid femur without anteroventral depression near base P. histrio
(Lepeletier)
- Tergum 1 without an acarinarium under its apical margin; tergum 2 with basal transverse groove pitted at least laterally (Fig. 7.15). Tergum 2 often with a pair of yellow spots (Fig. 7.66; small and dark ferruginous in S. lineatifrons, if present), apical fascia always developed. Male mid femur with anteroventral depression near base (as in Fig. 7.36) 16
16. Interantennal spot parallel-sided or decreasing in width from interantennal prominence towards upper end (Fig. 7.33). Pronotal carina interrupted or indistinct medially. Tergum 1 largely ferruginous; tergum 2 rarely with a pair of obscure ferruginous discal spots (Fig. 7.65). Yellow markings of body (except male clypeus) more or less suffused with reddish (Fig. 7.33). Male: clypeus coarsely punctate (as in Fig. 7.17). Female: clypeus with crescent-shaped dorsal mark (Fig. 7.33) (U.S.: VA southward) S. lineatifrons
Bohart
- Interantennal spot increasing in width dorsally (Fig. 7.34). Pronotal carina complete and well defined medially (similar to Fig. 2.12). Tergum 1 without ferruginous markings in specimens from northeastern states; tergum 2 with a pair of yellow spots (Fig. 7.66; always present in male?). Yellow markings of body deep yellow in northeastern specimens. Male: clypeus finely punctate (Fig. C58.3). Female: clypeus with transverse dorsal mark, not or hardly emarginate ventrally (Fig. 7.34) (U.S.: NY southward) S. histrionalis
(Robertson),
in part
17. Transverse basal groove of tergum 2 shining, with complete row of deep pits (Fig. 7.16). Tergum 3 with complete or nearly complete apical fascia (Fig. 7.16; rare exceptions). Male: base of fore femur with uniform, extremely short pubescence ventrally (as in Fig. 7.13); base of mid femur not at all depressed anteroventrally. Female: apical tooth of mandible as long as second and third tooth combined* (Fig. 7.37). [Pale markings of body usually pale yellow to ivory (paler in female), at least on posterior terga. Tergum 2 with apical margin scarcely thickened (thickness ≤ 0.6x mid ocellar diameter) (Fig. 7.67). Male flagellum obscure reddish to black beneath.] S. kennicottianus
(de Saussure)
- Basal groove of tergum 2 at least medially without pits (sculpture similar to Fig. 7.14); sometimes strongly pitted laterally but then surface dulled by fine rugosity. Tergum 3 with fascia interrupted medially or absent, very rarely complete. Male: base of fore femur ventrally with scattered longish hairs (length up to 0.4x mid ocellar diameter) among extremely short pubescence (similar to Fig. 7.12); base of mid femur slightly to distinctly depressed anteroventrally (Fig. 7.36). Female: apical tooth of mandible subequal in length to second* (Fig. 7.38) 18
  * Note: apical tooth often significantly shortened through wear in older specimens.  
18. Pronotal carina complete and well defined medially (similar to Fig. 2.12). Clypeus with very shallow apical emargination (depth less than 0.3x mid ocellar diameter; Fig. 7.34), finely punctate in male (Fig. C58.3). Basal groove of tergum 2 shallowly pitted laterally (Fig. 7.15). Male: flagellum dark beneath; clypeus yellow; apical margin of tergum 2 scarcely thickened (thickness rarely up to 0.8x mid ocellar diameter; Fig. 7.66); interantennal spot extending to clypeus ventrally, distinctly widening dorsally (as in Fig. 7.18). Female: dorsal half of clypeus with transverse mark, not or hardly emarginate ventrally (Fig. 7.34); femora either with brown or blackish basal areas gradually merging into yellow apical areas or largely ferruginous. [Pale markings of body yellow to orange yellow.] (U.S.: NY southward) S. histrionalis
(Robertson),
in part
- Pronotal carina interrupted medially. Clypeus with deeper apical emargination (depth usually over 0.5x mid ocellar diameter; Fig. 7.39), coarsely punctate in male (e.g., Fig. C60.3). Tergum 2 with basal groove finely wrinkled but not pitted (e.g., Fig. 7.40). Male: flagellum often yellowish beneath, if dark then clypeus almost always with black apical or discal markings (Fig. C46.4) and/or apical margin of tergum 2 thickened to at least one mid ocellar diameter (Fig. 7.55); interantennal spot very rarely extending to clypeus or widening dorsally. Female: dorsal half of clypeus with crescent-shaped pale mark (sometimes confluent with ventral spots), with a pair of spots or unmarked; femora black and yellow, without extensive intervening brownish areas (e.g., Fig. 7.54) 19
19. Tergum 2 with basal groove slightly concave immediately before subbasal declivity (Fig. 7.41, lateral view), the declivity with denser punctation than remainder of tergum but punctures only slightly smaller, well defined and not confluent; interspaces as smooth as elsewhere on tergum, not granulose (Fig. 7.43). Male: flagellum extensively yellow below; tergum 2 with a pair of yellow discal spots (Fig. 7.68). Female: apical half of clypeus with a pair of yellow spots (Fig. 7.39), sometimes confluent with yellow basal mark (U.S.: MA southward) S. krombeini
Bohart
- Tergum 2 with basal groove flat anterior to subbasal declivity (Fig. 7.42), the declivity with punctation becoming increasingly dense and small anteriorly; punctures just behind basal groove noticeably small, more or less confluent and not clearly differentiated from finely rugose interspaces (Fig. 7.44). Male: flagellum often black, if extensively yellow below then tergum 2 without discal spots. Female: clypeus very rarely with yellow spots in apical half 20
20. Male (seven metasomal segments) 21
- Female (six metasomal segments) 22
21. Flagellum black or with restricted obscure yellowish areas beneath; free margin of clypeus usually narrowly black (Fig. C46.4), clypeal disc sometimes also marked with black (as in Fig. 7.17). Markings of body bright yellow. Tergum 2 occasionally with a pair of yellow discal spots (Fig. 7.55). Aedeagus conspicuously constricted near middle (Fig. 7.45) P. pedestris
(de Saussure)
- Flagellum yellow beneath; apical margin of clypeus yellow except sometimes laterally; clypeal disc yellow. Markings of body often pale yellow (as in Fig. 7.56). Tergum 2 without pale discal spots. Aedeagus slightly narrowed near middle, not constricted (Fig. 7.46) P. pensylvanicus
(de Saussure)
22. Scutum with yellow posteromedial spot (as in Figs 7.19–20). Clypeus with paired dorsal spots, often confluent and forming a single crescent-shaped mark (exceptionally clypeus entirely black). [Tergum 1 frequently, tergum 2 almost always, with yellow discal spots (Fig. 7.54).] P. pedestris
(de Saussure),
in part
- Scutum without pale posteromedial spot. Clypeus with a pair of separate, yellow dorsal spots or entirely black 23
23. Tergum 2 without pale discal spots (Fig. 7.56; or else markings somewhat pale yellow). Markings of body pale to bright yellow (Fig. 7.56) P. pensylvanicus
(de Saussure),
in part
- Tergum 2 with a pair of discal yellow spots; markings of body bright yellow (Fig. 7.54) P. pensylvanicus
or P. pedestris,
in part

 

Metasoma of Parancistrocerus species

Parancistrocerus

 

Metasoma of Stenodynerus species

Stenodynerus

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