

CJAI 05, February 19, 2008
doi: 10.3752/cjai.2008.05



Polistes Latreille

The genus Polistes occurs in all biogeographic regions and includes 203 described species (Carpenter 1996a, Carpenter in litt.). The Nearctic fauna consists of 24 native or naturalized species, 11 of which occur in the northeast. Two species were newly discovered during this project and will be formally described elsewhere. Two adventitious species have each been recorded once from the area, one of western Nearctic and one of Neotropical origin. The northeastern species fall in two subgenera. The nominate subgenus is represented by the single, introduced Palaearctic species P. dominula. Formerly, the native Nearctic species were classified into five subgenera, two of which, Aphanilopterus and Fuscopolistes, are represented in the northeast (Richards 1973, 1978). Carpenter (1996a, 1996b) synonymized Fuscopolistes and three other subgenera with Aphanilopterus, but a recent study provided renewed support for the validity of the former (Pickett et al. 2006). Below, we refer to the species formerly placed in Fuscopolistes as the P. fuscatus-group (comprised of P. bellicosus, P. carolina, P. dorsalis, P. fuscatus, P. metricus, P. perplexus, Polistes sp. A and sp. B).

References. – Carpenter, 1996a (catalogue of World species, distribution), 1996b (phylogeny of subgenera); Pickett et al., 2006 (phylogeny of subgenera); Bequaert, 1940a (taxonomy of Canadian and U.S. species, key).

10. Key to northeastern Nearctic Polistes species

Note: two adventitious species, the western P. aurifer de Saussure (one record from Prince Edward Island) and the Caribbean P. dominicus (Vallot) (one record from Ontario) are not included in the key (for diagnoses see species treatments).

1. Flagellum almost entirely bright orange (excluding black dorsal streak in basal 3/4 of flagellomere I, Fig. 10.4). Scutum black, with a pair of yellow spots in anterior half (Fig. 10.3; the spots exceptionally absent). Centre of mesopleuron with coarse, contiguous punctures; omaulus present, dorsally almost extending to dorsal groove of mesopleuron (Fig. 10.1). Head and body (excluding appendages) entirely black and yellow (Figs 10.3–4, 10.44). Female: scape black above, yellow below; clypeus yellow, with or without black central spot(s) (Fig. 10.4) P. (Polistes) dominula
- Flagellum usually brownish to black dorsally (Figs 10.18–19), if partly orange then at least middle portion infuscated (Fig. 10.5). Yellow scutal markings rarely present but if so then scutum predominantly ferruginous. Centre of mesopleuron with dense, small punctures, sometimes interspersed with scattered macropunctures; omaulus absent (Fig. 10.2). Head and body usually with well-developed ferruginous markings. Female: scape reddish to ferruginous below; clypeus usually marked with ferruginous areas, if black and yellow, then black spot attaining dorsal margin P. (Aphanilopterus)
2. Metasomal segment 1 more slender, tergum 1 at least as long as broad (measured from base of anterior declivity to hind margin; Fig. 10.6), in profile with shallow depression near 2/3 (Fig. 10.8). Apical flagellomeres orange, contrasting with blackish median flagellomeres (Fig. 10.5). Head behind occipital carina with dense fringe of relatively long, erect hairs (length up to one mid ocellar diameter, best seen in anterolateral view; Fig. 10.10) 3
- Metasomal segment 1 stout, tergum 1 broader than long (Fig. 10.7), in profile more evenly rounded (Fig. 10.9). Flagellum more or less darkened on most of dorsal surface, at most becoming gradually paler towards apex, but never with contrasting pattern (Figs 10.18–19). Head behind occipital carina with short fringe of erect hairs (length less than 0.5x mid ocellar diameter, plus a few scattered longer hairs; Fig. 10.11) P. fuscatus-group
3. Mesopleuron without macropunctures. Head, meso- and metasoma conspicuously marked with yellow, notably on mesopleuron and propodeum (Figs 10.10, 10.12, 10.45). Metasoma predominantly ferruginous with apical yellow fasciae on most or all segments, base of terga more or less black (Fig. 10.45) (ON: adventitious; U.S.: from NJ southward) P. exclamans
- Mesopleuron with small but distinct macropunctures (Fig. 10.13). Yellow markings absent or inconspicuous on head, meso- and metasoma except well-developed apical fascia on tergum 1 (Fig. 10.46). Ground colour of metasoma black except for ferruginous mark on tergum 1 and sometimes a pair of ferruginous spots on tergum 2 (Fig. 10.46) (U.S.: NY and MA southward) P. annularis
4. Micropunctures of mesosoma and female clypeus smaller than in other species, the integument therefore more shining, with a ‘greasy’ lustre (Fig. 10.14). Eye with scattered, minute hairs (visible at 20x magnification). Pronotal fovea of female and most males either absent (Fig. 10.14) or developed as a minute, shallow pit. Propodeal orifice distinctly and fairly abruptly narrowed dorsally (Fig. 10.16). Female: flagellomeres I–VIII or IX with relatively long, bristly hairs posteriorly and dorsally (hairs becoming sparser and shorter towards apex of flagellum; Fig. 10.18) (U.S.: DE and IL southward; distribution insufficiently known) Polistes sp. A
- Micropunctures of clypeus and mesosoma coarser, the integument less shining, without ‘greasy’ lustre (e.g., Fig. 10.15). Eye usually bare; hairs, if present, only visible at high magnification. Pronotal fovea usually well developed, penetrating pronotum (Fig. 10.15); exceptionally minute and shallow. Propodeal orifice at most slightly and gradually narrowed dorsally (Fig. 10.17). Female: only flagellomeres I–II (in P. perplexus* often I–VI) with bristly hairs posteriorly and dorsally, these hairs shorter (Fig. 10.19) 5
  * Easily separated from species A by the entirely pubescent gena (see couplet 8).  
5. Female (six metasomal segments) 6
- Male (seven metasomal segments) 15
6. Metasoma without yellow markings, or only tergum 1 with yellow apical fascia (Figs 10.48–49, 10.52–54, 10.56) 7
- Metasoma with yellow markings on tergum 1 and at least one of segments 2–6 (Figs 10.47, 10.50–51, 10.55, 10.57) 12
Mesosoma, metasoma, and legs almost entirely ferruginous (Figs 10.48–49, C72.1, C72.3, C79.1, C79.3), black or dark brown areas, if present, restricted to one or more of the following areas: small spot in front of pronotal carina, certain sutures of mesosoma, margins and sometimes one or three longitudinal stripes on scutum, median groove of propodeum, narrow bases of terga 2 or 3 (rarely), posterior bases of coxae, and apex of hind tibia medially
- At least either mesosoma, metasoma or legs with more extensive black areas than above 9
8. Malar space and gena uniformly covered by fine, appressed silvery pubescence arising from minute punctures, interspersed by a few scattered macrosetae arising from larger punctures (Fig. 10.20). Propodeum coarsely ridged (Fig. 10.37) (U.S.: from MD southward) P. perplexus
- Malar space and lower gena bare except for a few scattered macrosetae arising from larger punctures; only upper 3/4 of gena with fine, appressed silvery pubescence (Fig. 10.21). Propodeum usually with fine or no ridging (Fig. 10.38) (ON: adventitious; U.S.: from NY southward) P. carolina
9. One or more of the following features present: clypeal disc marked with black; mesopleuron with yellow dorsal spot (Fig. 10.28); at least one of metasomal segments 3–6 with ferruginous markings P. fuscatus
in part
- Clypeal disc entirely ferruginous (Fig. 10.24). Mesopleuron lacking yellow dorsal spot. Metasomal segments 3–6 entirely black (Fig. 10.52–54) 10
10. Sternum 2 strongly convex (Fig. 10.22). Black ocellar spot (if present) either separate from (Fig. 10.24), or in rare cases, very narrowly connected to black antennal spot(s) (if present). Mesopleuron and propodeum with ferruginous marks (ON: Pelee I.; eastern U.S.) P. metricus
- Sternum 2 moderately convex (Fig. 10.23). Black ocellar marking usually broadly connected to black antennal marking (Fig. 10.25). Mesopleuron and/or propodeum sometimes entirely black 11
11. Sterna 3–5 with central area densely punctate, the interspaces less than one puncture diameter; punctation mostly fine, with few, regularly spaced, larger punctures (Fig. 10.39). Mesopleuron sometimes entirely black P. fuscatus
in part
- Sterna 3–5 with central area more coarsely punctate, the punctures rather spaced and in some areas two puncture diameters apart; punctures of sparsely punctate areas either uniform in size or large punctures more numerous than small punctures (Fig. 10.40). Mesopleuron marked with ferruginous (MD, WV, VA; distribution insufficiently known) Polistes sp. B
12 Hind trochanter beyond basal constriction, and usually hind femur, with more or less developed black or brown markings 13
- Hind trochanter beyond basal constriction (and hind femur) ferruginous, without black or brown markings 14
13. Small species (fore wing length 10–13 mm). Hind femur with black or brown mark forming a complete ring near base. Clypeal disc not marked with black or dark brown; black frontal markings, if present, not connecting ocelli to antennal bases (Fig. 10.29) (U.S.: southern MA southward) P. dorsalis
- Larger species (fore wing length 13–17 mm, exceptionally as short as 11 mm). Hind femur with black or brown mark often interrupted dorsally, if forming a complete ring then clypeal disc marked with black or dark brown, and black frontal marking connecting ocelli to antennal bases (Fig. 10.25) P. fuscatus
in part
14. Clypeus with at least half of disc yellow (Fig. 1.11) (ON: adventitious; U.S.: NY southward, mainly coastal) P. bellicosus
- Clypeus with yellow markings, if present, occupying less than half of disc (Fig. 10.25) P. fuscatus
in part*
  * Note. Only a very small percentage of northeastern P. fuscatus key to this couplet. In some cases their separation from P. bellicosus is difficult.  
15. Sternum 7 with prominent median tubercle, clearly visible in profile (Fig. 10.31). All flagellomeres with tyloids dull orange-yellow; basal 2/5 of flagellomere XI nearly parallel-sided in posterior view (Fig. 10.32). [Anterior and ventral surfaces of flagellum concolorous yellow to orange from base to apex (as in Fig. 10.36)] P. dorsalis (Fabricius)
- Sternum 7 with weak median tubercle, not visible in profile. Apical flagellomeres with tyloids shining black, brown, or orange-yellow; flagellomere XI often more or less strongly tapered apically (Fig. 10.33) 16
16. Flagellomeres VIII–X dark brown to black (Figs 10.33, 10.34–35), their tyloids at most slightly paler than black dorsal surface 17
- Flagellomeres VIII–X at least in part yellow to reddish brown (Figs 10.32, 10.36), their tyloids usually much paler than black to dark brown dorsal surface (rarely flagellomeres entirely reddish yellow) 18
17. Flagellomeres I–V with anterior surface dark reddish brown, weakly contrasting with black to slightly darker brown anterior surface of apical flagellomeres (Fig. 10.35). Aedeagal teeth small; each row of teeth stopping well before apex of median expansion of aedeagus (Fig. 10.43). Metasoma largely black, rarely with ferruginous spots on terga 1 or 2, whitish apical fascia usually present on tergum 1 only (rarely also on 2 and 3) Polistes sp. B
- Flagellomeres I–V with anterior surface yellow to orange, strongly contrasting with black apical flagellomeres (Fig. 10.34). Aedeagal teeth large; each row of teeth extending basally almost to apex of median expansion of aedeagus (Fig. 10.41, 10.42). Metasoma usually with either ferruginous or yellow markings more extensive than above P. fuscatus
18. Metasoma with ferruginous markings, if present, restricted to terga 1 and 2; yellow apical fascia present at most on tergum 1 P. metricus
- Metasoma with ferruginous markings on all terga (sometimes very small on terga 1, 3 and 4); sometimes with well-developed yellow apical fasciae on several terga 19
19. Yellow markings well developed: at least metasomal terga 1–3 with apical fasciae; upper mesopleuron with spot below pronotal lobe (similar to Fig. 10.28). Mesopleuron often without ferruginous markings P. bellicosus
- Yellow markings much more reduced: rarely metasomal tergum 1 with apical fascia; upper mesopleuron almost always without spot, if rarely present, the spot ill-defined. Mesopleuron extensively ferruginous 20
20. Propodeum with coarse transverse ridging (Fig. 10.37) P. perplexus
- Propodeum usually smooth or with very fine transverse ridging (Fig. 10.38), exceptionally with coarser ridging P. carolina


Metasoma of Polistes species



