Key to the Western Palaearctic species

The female of Chelostoma negevense is unknown.

Females

1 Posterior and lateral surface of propodeum completely dull except for more or less polished propodeal pit............... 2

1* Posterior and lateral surface of propodeum largely polished.................................................... 4

2 Clypeus apically dentate and neither with medioapical lamella nor with two processes projecting sidewards. Hairs of metasomal scopa not plumose. Labrum apically rounded. Lowermost part of genal area not inflated. (Body length 7–9.5 mm; Maghreb).................................................................................. Chelostoma carinulum

2* Clypeus with medioapical lamella or with two processes projecting sidewards. Hairs of metasomal scopa plumose. Labrum apically truncate to slightly emarginate. Lowermost part of genal area inflated. Chelostoma florisomne species group...... 3

3 Clypeus flat and densely punctate over most of its surface and medioapically with projecting lamella, which is apically rounded, truncate or slightly to deeply emarginate. (Body length 8–10.5 mm; Europe, Turkey, Caucasus).... Chelostoma florisomne

3* Clypeus strongly declivous and impuncate in its apical two thirds and with two short, slender and apically rounded processes projecting sidewards. (Body length 7–8 mm; Sicily).......................................... Chelostoma stefanii

4 Proboscis very long (Fig. 10, 19, 30, 40), surpassing coxa of fore leg when folded; second segment of labial palpus distinctly longer than compound eye.............................................................................. 5

4* Proboscis short (Fig. 1, 49, 66), not reaching coxa of fore leg when folded; second segment of labial palpus distinctly shorter than compound eye................................................................................... 11

5 Smaller species, body length less than 8 mm. Terga 2–3 basally not or only weakly constricted (Fig. 30, 40). Labrum at most 2× as long as apically wide (Fig. 21). Chelostoma meronense species group....................................... 6

5* Larger species, body length at least 8 mm. Terga 2–3 basally distinctly constricted. Labrum at least 2.5× as long as apically wide (Fig. 13). Chelostoma grande species group................................................................ 8

6 Anterior surface of coxa of fore leg densely punctate with interspaces rarely exceeding the diameter of one puncture (Fig. 34). Head 1.1–1.2× as long as wide (Fig. 32). Basal area of propodeum medially about as long as metanotum (Fig. 33). (Body length 6.5–7.5 mm; Israel)................................................................. Chelostoma meronense

6* Anterior surface of coxa of fore leg medially sparsely punctate with interspaces reaching the diameter of several punctures (Fig. 23). Head 1.3–1.4× as long as wide (Fig. 21). Basal area of propodeum medially slightly to distinctly longer than metanotum (Fig. 22, 43)......................................................................................... 7

7 Third segment of labial palpus as long as or shorter than fourth segment. Second segment of labial palpus distinctly less than 2× as long as compound eye. Proboscis not reaching coxa of middle leg when folded. Labrum about 1.75× as long as apically wide (Body length 6–7 mm; Turkey, Iraq).......................................... Chelostoma dolichocephalum

7* Third segment of labial palpus about 2.5× as long as fourth segment (Fig. 42). Second segment of labial palpus slightly more than 2× as long as compound eye. Proboscis reaching coxa of middle leg when folded. Labrum about 2× as long as apically wide. … (Body length 7.5 mm; Turkey, Iraq)............................................ Chelostoma miripalpum

8 Mandible shorter and wider with three teeth. Labrum 2.5–3× as long as apically wide. Transition between basal and apical part of clypeus in lateral view rounded rather than angled. (Body length 8–10.5 mm; southeastern Europe, Turkey, Levant).......................................................................................... Chelostoma lucens

8* Mandible longer and more slender with two teeth. Labrum more than 3× as long as apically wide (Fig. 13). Transition between basal and apical part of clypeus in lateral view angled rather than rounded (Fig. 12)................................. 9

9 Labrum medially with polished longitudinal tubercle, its mediobasal part almost flat. Strongly declivous apical part of clypeus medially longer than flat basal part. Punctation of declivous apical part of clypeus distinctly more scattered than that of basal part.Apex of labrum strongly projecting upwards. (Body length 10–14 mm; mountains of southwestern, central and southeastern Europe).............................................................................. Chelostoma grande

9* Labrum medially without polished longitudinal tubercle, its mediobasal part slightly concave and laterally bordered by two narrow longitudinal swellings (Fig. 13). Strongly declivous apical part of clypeus medially shorter than flat basal part (Fig. 12). Punctation of declivous apical part of clypeus as dense as that of basal part. Apex of labrum flat to weakly projecting upwards............................................................................................ 10

10 Declivous apical part of clypeus bent a right angles to flat basal part and only about one fourth as long as basal part (Fig. 12). Antennal segment 3 about 1.75× as long as wide. Basal area of propodeum medially almost as long as metanotum (Fig. 14). (Body length 10 mm; Turkey, Iran)..................................................... Chelostoma scabiosae

10* Declivous apical part of clypeus bent at an angle of about 120 degrees to flat basal part and at least half as long as basal part. Antennal segment 3 about 1.5× as long as wide. Basal area of propodeum medially usually only about half as long as metanotum. (Body length 8–13 mm; Greece)........................................... Chelostoma transversum

11 Base of labrum medially with polished roundish tubercle. Inner margin of mandible with distinct triangular tooth shortly before its middle. Basal area of propodeum distinctly longer than metanotum. (Body length 6–8 mm; Greece, Turkey, Cyprus, Iraq, Iran, Levant).......................................................................... Chelostoma diodon

11* Base of labrum medially flat. Inner margin of mandible without distinct tooth between its base and middle. Basal area of propodeum shorter than, as long as or slightly longer than metanotum........................................... 12

12 Basal area of propodeum impressed, bordered by raised transverse ridge along its entire posterior margin and with rather coarse longitudinal carinae (Fig. 55)........................................................................... 13

12* Basal area of propodeum flat, not bordered by raised ridge along its entire posterior margin and usually with rather fine longitudinal carinae (Fig. 5). Chelostoma emarginatum species group........................................... 16

13 Apical margin of labrum medially with small triangular incision. Narrow transversal zone along posterior margin of basal area of propodeum distinctly shagreened. Punctation of clypeus laterally less dense with interspaces reaching the diameter of up to one and a half to two, rarely more punctures. (Body length 6.5–9 mm; Turkey, Cyprus, Iraq, Levant)..................................................................................................... Chelostoma comosum

13* Apical margin of labrum shallowly emarginate over entire width. Narrow transversal zone along posterior margin of basal area of propodeum polished to imperceivably shagreened. Punctation of clypeus laterally denser with interspaces not exceeding the diameter of one puncture. Chelostoma mocsaryi species group................................................ 14

14 Inner margin of mandible without tooth between base and second outermost tooth, rendering mandible two-toothed (Fig. 69). Vertex longer: distance between outer margins of posterior ocelli about as long as distance between anterior margin of lateral ocellus and occipital margin (Fig. 68). (Body length 8–9 mm; Turkey)........................ Chelostoma ornithogali

14* Inner margin of mandible with distinct triangular tooth between base and second outermost tooth, rendering mandible three-toothed (Fig. 53). Vertex shorter: distance between outer margins of posterior ocelli distinctly longer than distance between anterior margin of lateral ocellus and occipital margin (Fig. 51)................................................ 15

15 Body length not exceeding 7 mm. In lateral view, upper side of labrum almost straight over its entire length without apical angle. Punctate apicalmost part of labrum medially about 0.5× as long as apically wide and transitioning without ledge into impunctate more basal part (Fig. 52). Impunctate basal part of labrum usually completely shagreened, laterally without narrow polished longitudinal groove along labral margin (only visible if labrum is fully exposed). Clypeus medially flat to slightly concave, which is best seen when it is viewed from below (Fig. 52). (Body length 6–7 mm; Turkey, Iraq, Iran)......................................................................................... Chelostoma kurdistanicum

15* Body length mostly exceeding 7 mm. In lateral view, punctate apicalmost part of labrum slightly angled from impunctate more basal part. Punctate apicalmost part of labrum medially 0.7-1× as long as apically wide and usually more or less distinctly separated from impunctate more basal part by inconspicuous edge. Impunctate basal part of labrum laterally often with narrow polished longitudinal groove along labral margin (only visible if labrum is fully exposed). Clypeus medially evenly convex, which is best seen when it is viewed from below. (Body length 6.5–9.5 mm; southern Europe, Turkey, Cyprus, Caucasus, Iraq, Iran, Levant)........................................................................ Chelostoma mocsaryi

16 Apical margin of labrum medially with small triangular to semicircular incision (Fig. 3). Mandible distinctly three-toothed with basalmost tooth about as large as second outermost tooth and with almost equal distances between tips of the three teeth (Fig. 4). Body length usually less than 8 mm. (Body length 6–8 mm; Levant)........................ Chelostoma levantense

16* Apical margin of labrum truncate to slightly rounded, without median incision. Mandible two-toothed or indistinctly three-toothed; in the latter case, basalmost tooth much smaller than second outermost tooth and distance between tips of outermost two teeth much shorter than distance between tips of second outermost and basalmost tooth. Body length often more than 7.5 mm ............................................................................................... 17

17 Apex of labrum distinctly projecting upwards when seen in profile. Inner margin of mandible with small but distinct tooth. (Body length 6.5–9.5 mm; southwestern Europe, Maghreb).................................. Chelostoma edentulum

17* Apex of labrum nearly flat when seen in profile, not distinctly projecting upwards. Inner margin of mandible straight, rarely with very small and nearly imperceivable tubercle. (Body length 7–9.5 mm; southern Europe, Turkey, Caucasus, Iraq, Iran, Turkmenistan)................................................................... Chelostoma emarginatum

Males

1 Posterior and lateral surface of propodeum completely dull except for more or less polished propodeal pit............... 2

1* Posterior and lateral surface of propodeum largely polished.................................................... 3

2 Antennal segments 5–9 cylindrical. Lowermost part of genal area with long whitish hairs. Gena along compound eye without felt-like pilosity. Median longitudinal furrow at posterior end of mesosternum shallow. (Body length 7–9 mm; Maghreb)..................................................................................... Chelostoma carinulum

2* Antennal segments (5)6–8(9) serrate. Lowermost part of genal area with dense tuft of short whitish to yellowish hairs. Gena on narrow zone along compound eye with felt-like whitish to yellowish pilosity. Median longitudinal furrow at posterior end of mesosternum deep. No morphological characters are known to distinguish the following two species; however, identification is possible based on the non-overlapping distribution areas.............................................................................................. Chelostoma florisomne (Body length 7–11 mm; Europe, Turkey, Caucasus), Chelostoma stefanii (Body length 6.5–7.5 mm; Sicily)

3 Apical margin of sternum 3 with row of stiff yellowish bristles (Fig. 29, 39, 48). Chelostoma meronense species group..... 4

3* Apical margin of sternum 3 without row of stiff bristles....................................................... 6

4 Hypostomal area without tooth-like projection. Third segment of labial palpus about 2.5× as long as fourth segment (Fig. 42). Antenna uniformly dark brown to black (Fig. 44). Ventral base of apical teeth of tergum 7 with large tooth-like projection, the tip of which is clearly visible when tergum 7 is viewed from above (Fig. 45). (Body length 8–8.5 mm; Turkey, Iraq)........................................................................................ Chelostoma miripalpum

4* Hypostomal area with tooth-like projection (Fig. 24, 36). Third segment of labial palpus as long as fourth segment or shorter. Anterior side of antennal flagellum predominantly yellowish-white to yellowish-red (Fig. 25, 35). Ventral base of apical teeth of tergum 7 with only small tooth-like projection, the tip of which is not visible when tergum 7 is viewed from above (Fig. 26, 37)................................................................................................. 5

5 Antennal segments 5–12 transversally asymmetrical with lower margin apically prolonged into acute tip, shorter than wide to as long as wide and yellowish to yellowish-white on anterior side (Fig. 25). Last antennal segment roundish, distinctly button-like (Fig. 25). Tooth-like projection on hypostomal area roughly triangular in lateral view (Fig. 24). Genal area along lower margin of compound eye distinctly impressed and almost impunctate. Basal area of propodeum medially distinctly longer than metanotum (Fig. 22). Median impression on posterior half of mesosternum narrow and almost parallel-sided. Anterior part of median projection of sternum 2 constricted laterally with preapical lateral margins concave (Fig. 27, 28). Patches of short black thorns of sternum 3 restricted to small spots on each side of sternal impression (Fig. 29). (Body length 8–8.5 mm; Turkey, Iraq)....................................................................... Chelostoma dolichocephalum

5* Antennal segments 5–12 transversally symmetrical, longer than wide and yellowish-red on anterior side (Fig. 35). Last antennal segment elongated oval, not distinctly button-like (Fig. 35). Tooth-like projection on hypostomal area roughly rectangular in lateral view (Fig. 36). Genal area along lower margin of compound eye not distinctly impressed and densely punctate. Basal area of propodeum medially as long as to slightly longer than metanotum (Fig. 33). Median impression on posterior half of mesosternum widely triangular in shape. Anterior part of median projection of sternum 2 evenly rounded with preapical lateral margins convex (Fig. 39). Patches of short black thorns of sternum 3 narrow and curved, covering entire sides of sternal impression (Fig. 39). (Body length 7.5–8.5 mm; Israel).................................... Chelostoma meronense

6 Proboscis very long (Fig. 11), surpassing coxa of fore leg when folded; second segment of labial palpus distinctly longer than compound eye. Hypostomal area with sharp and distinct tooth-like projection of triangular shape formed by each hypostomal carina in its basal half (Fig. 16). Chelostoma grande species group.............................................. 7

6* Proboscis short (Fig. 2, 50, 67), not reaching coxa of fore leg when folded; second segment of labial palpus distinctly shorter than compound eye. Hypostomal area without distinct projection formed by each hypostomal carina in its basal half, but sometimes with tubercle or projection arising laterally to each hypostomal carina (Fig. 54, 60, 70)..................... 9

7 Median projection of sternum 2 half-elliptical in shape, its anterior margin evenly rounded. Sternum 3 laterally with two long and slender processes each bearing patch of short black thorns. (Body length 11–15 mm; mountains of southwestern, central and southeastern Europe)................................................................ Chelostoma grande

7* Median projection of sternum 2 roof-shaped, its anterior margin straight to very slightly curved (Fig. 17). Sternum 3 without long and slender lateral processes (Fig. 17)................................................................. 8

8 Stepped apical part of gonoforceps on inner side with several long and backwards directed hairs, the longest of which are more than half as long as apical part of gonoforceps. Hairs forming loose band at apical margin of sternum 4 slightly more than half as long as membraneous appendage at apical margin of sternum 4. No morphological characters are known to distinguish the following two species; however, identification is possible based on the apparently non-overlapping distribution areas....................................... Chelostoma lucens (Body length 8.5–11 mm; southeastern Europe, Turkey, Levant), Chelostoma transversum (Body length 9.5–12 mm; Greece).

8* Stepped apical part of gonoforceps on inner side almost hairless (Fig. 18). Hairs forming loose band at apical margin of sternum 4 slightly less than half as long as membraneous appendage at apical margin of sternum 4 (Fig. 17). (Body length 10-12 mm; Turkey, Iran)....................................................................... Chelostoma scabiosae

9 Hypostomal area with two small tubercles or two cone- to tooth-shaped projections arising laterally to hypostomal carina (Fig. 54, 60, 70). Tergum 7 in addition to upper teeth with two shorter lower teeth that project backwards in lateral view. Genal area along lower margin of compound eye with polished to more or less shagreened, impunctate, hairless and sometimes slightly concave zone (Fig. 61). Chelostoma mocsaryi species group.................................................. 10

9* Hypostomal area without tubercles or projections arising laterally to hypostomal carina. Tergum 7 without lower teeth or only with right-angled edges that do not project backwards in lateral view. Genal area along lower margin of compound eye without well delimited impunctate and hairless zone............................................................... 13

10 Anterior margin of median projection of sternum 2 prolonged into long and narrow lamella projecting at an angle of 100–120 degrees from sternal surface. Polished impunctate zone of genal area along lower margin of compound eye about as wide as width of antennal flagellum in its apical half. (Body length 8–11 mm; southern Europe, Turkey, Cyprus, Caucasus, Iraq, Iran, Levant)............................................................................ Chelostoma mocsaryi

10* Anterior margin of median projection of sternum 2 not prolonged into almost vertically projecting lamella (Fig. 58, 64, 73). Polished impunctate zone of genal area along lower margin of compound eye narrower than width of antennal flagellum in its apical half (Fig. 61).................................................................................. 11

11 Hypostomal area with small tubercle adjacent to hypostomal carina on each side (Fig. 54). Median projection of sternum 2 narrower (Fig. 58), its anterior margin angular but neither sharp nor overhanging its anterior surface; in lateral view, angle between anterior and ventral surface of median projection almost 90 degrees (Fig. 57). Patches of short black thorns on sternum 3 small, roundish and separated from each other by a distance at least twice as large as maximum width of thorn patch (Fig. 58). (Body length 6.5–8 mm; Turkey, Iraq, Iran).......................................... Chelostoma kurdistanicum

11* Hypostomal area with tooth-like projection adjacent to hypostomal carina on each side (Fig. 60, 70). Median projection of sternum 2 wider (Fig. 64, 73), its anterior margin sharp and slightly overhanging its anterior surface; in lateral view angle between anterior and ventral surface of median projection much less than 90 degrees (Fig. 63, 72). Patches of black thorns on sternum 3 of varying size.............................................................................. 12

12 Patches of black thorns on sternum 3 small, roundish and separated from each other by distance several times larger than maximum width of thorn patch (Fig. 64). Upper teeth of tergum 7 wider, basally slightly constricted, medially weakly widened and apically slightly curved, largely hiding lower teeth when seen from above (Fig. 62). Apical part of gonoforceps laterally distinctly flattened, its apex almost linear when seen from behind (Fig. 65). (Body length 8.5–9.5 mm; Israel).............................................................................................. Chelostoma negevense

12* Patches of black thorns on sternum 3 larger, roughly rectangular and separated from each other by distance shorter than to maximally as long as maximum width of thorn patch (Fig. 73). Upper teeth of tergum 7 narrower and parallel-sided, not hiding lower teeth when seen from above (Fig. 71). Apical part of gonoforceps laterally not flattened, its apex roof-shaped when seen from behind. (Body length 7–8 mm; Turkey)............................................ Chelostoma ornithogali

13 Apical teeth of tergum 7 slender and more than twice as long as basally wide. Apical margin of sternum 5 with one median and two lateral tails of long yellowish bristles. Sternum 3 medioapically with semicircular swelling laterally bearing two small patches of short black thorns. Median projection of sternum 2 small, occupying about one fifth of sternal width, horseshoeshaped, narrowly longitudinally impressed and with nearly horizontal surface parallel to main axis of body. (Body length 5.5–6.5 mm; Greece, Turkey, Cyprus, Iraq, Iran, Levant)....................................... Chelostoma diodon

13* Apical teeth of tergum 7 rather wide and slightly shorter to slightly longer than basally wide (Fig. 8). Apical margin of sternum 5 with uninterrupted comb of long yellowish bristles. Sternum 3 medioapically without semicircular swelling. Median projection of sternum 2 large, trapeziform to half-elliptical, widely concave and with ventral surface oblique and distinctly rising posteriorly..................................................................................... 14

14 Median projection of sternum 2 very large, occupying about half of sternal width, trapeziform and beset with long, dense and whitish pilosity along its sides. Basal area of propodeum impressed, bordered by raised transverse ridge along its entire posterior margin and with rather coarse longitudinal carinae. (Body length 7–10 mm; Turkey, Cyprus, Iraq, Levant)......................................................................................... Chelostoma comosum

14* Median projection of sternum 2 smaller, occupying about one third of sternal width, half-elliptical and without long and dense pilosity along its sides (Fig. 9). Basal area of propodeum flat, not bordered by raised ridge along its entire posterior margin and usually with rather fine longitudinal carinae (Fig. 5). Chelostoma emarginatum species group........................ 15

15 Tibial spur of fore leg apically broadly rounded, its posterior margin that faces away from basitarsus slightly concave. Long hairs protruding from apical part of gonoforceps yellowish-brown to dark brown. Minimal distance between inner margins of the two patches of short black thorns on sternum 3 larger than maximum diameter of one patch; an imaginary prolongation of lateral margin of median projection of sternum 2 usually touching outer margin of thorn patch. (Body length 8–10 mm; southwestern Europe, Maghreb)........................................................ Chelostoma edentulum

15* Tibial spur of fore leg apically slightly emarginate resulting in two small lobes, its posterior margin that faces away from basitarsus straight (Fig. 7). Long hairs protruding from apical part of gonoforceps whitish. Minimal distance between inner margins of the two patches of short black thorns on sternum 3 about the same as maximum diameter of one patch, rarely slightly shorter or slightly longer (Fig. 9); an imaginary prolongation of lateral margin of median projection of sternum 2 usually running beyond outer margin of thorn patch............................................................... 16

16 Vertex longer, distance between inner margins of lateral ocelli distinctly shorter than distance between posterior margin of lateral ocellus and occipital margin. Body length at least 7.5 mm. (Body length 7.5–10 mm; southern Europe, Turkey, Caucasus, Iraq, Iran, Turkmenistan).......................................................... Chelostoma emarginatum

16* Vertex shorter, distance between inner margins of lateral ocelli about as long as distance between posterior margin of lateral ocellus and occipital margin (Fig. 6). Body length at most 8 mm. (Body length 6–8 mm; Levant).... Chelostoma levantense