Leptometriella Roig-Alsina

A. Roig-Alsina, 2008, A revision of the South American bee genus Leptometriella Roig-Alsina (Hymenoptera, Apidae, Emphorini), Zootaxa 1688 (1), pp. 20-36 : 21-24

Leptometriella Roig-Alsina

Leptometriella Roig-Alsina, 1999: 23–24 .

Type species Leptometria tucumana Brèthes, 1910 .

Diadasina (Leptometriella) : Michener, 2000: 683; Michener, 2007: 704.

Bees 4.5–9.5 mm long, with distinct apical bands of hairs on T2–T4 (female) or T2–T6 (male). First flagellomere short, at most 1.4 times as long as its apical width. Labrum of female with flattened disc and preapical margin keeled, bearing median denticle ( Fig. 1 ); labrum of male with preapical margin irregularly carinate and also bearing median denticle. Mandible of female with small preapical tooth. Proboscis short, at rest barely reaching anterior coxae; second segment of labial palp at most 0.7 times as long as first; maxillary palp with brush of hairs on apex of second, and on entire third and fourth segments; postmentum broadened basally at union with lorum. Lateral carina of propleuron complete, strongly curved on anterior half. Metapostnotum with hairs usually restricted to area close to propodeal margin, in one species ( L. separata ) hairs covering lower two thirds of metapostnotum or more ( Fig. 2 ), but always metapostnotum bare on sides, and with bare band at least 0.2 times midlength of metanotum along midline. Hind tibia of female with distinct basitibial plate; outer surface with scopal hairs with short, straight branches pointing apicad. Hind basitarsus of female with strong apical projection bearing tuft of hairs; hind basitarsus of male arcuate. Arolia present; all claws with pointed apices in both sexes. Gradulus of S2 gently curved. Gradulus of T6 of female incomplete, always with a short apical portion present and in some species with basal portion continuing pygidial plate ( Figs. 12–13). Pygidial plate with sides concave, and apical portion narrow, parallel-sided.

Species groups

Three species groups can be recognized within Leptometriella. Each group has a characteristic shape and ornamentation of the hidden seventh sternum of the male ( Figs. 15, 19 , 23 ).

The tucumana species group, which includes L. tucumana , L. nigra , and L. hirsutula , is the most distinctive. In this group the mandible of the male is broadened preapically. The mandible is nearly twice as broad as the width of the acetabular groove between the groove and the inner margin ( Fig. 10); in other species ( Fig. 11), as well as in most emphorines, the mandible tapers apically, the inner margin being narrower, or as broad as, the groove. Only species of the emphorine genus Alepidosceles have a preapically broadened mandible, although more conspicuously than in the tucumana group. Current studies indicate that this broadened mandible is a derived condition, and has evolved independently twice within the tribe. Another characteristic of the group is the presence of a gradular carina on the basal part of the sixth tergum of the female, continuing laterad the raised margin of the pygidial plate ( Fig. 12); there is also present a short gradular carina restricted to the apical part of the tergum, but this posterior short carina is present in all the species of the genus. This type of gradular carina, with a basal and an apical portion, is an apomorphic condition for the group.

Leptometriella separata stands apart in its own species group. The seventh metasomal sternum of the male has the admedian lobes secondarily fused along the midline ( Fig. 20 ), a condition that is unique within the tribe. The eighth metasomal sternum of the male is only briefly split in the middle ( Fig. 21 ), while in the other species it is deeply incised ( Figs. 17 , 25 ). The vertex of the head in this species is strongly elevated behind the ocelli.

The third group includes L. monteana , L. minima , and L. boliviana . The structure of the male hidden metasomal sterna is remarkably similar in the group. The seventh sternum has the same outline ( Fig. 24 ), and the distribution and the length of the hairs is the same in the three species. Also similar are several characteristics of the male genital capsule, such as the length and shape of the gonostylus, the shape of the spatha, and the structure of the penis valve ( Fig. 22 ). Nevertheless, these characteristics may represent the plesiomorphic condition for the genus, and the group may prove in the future to be paraphyletic. Within the group, L. minima and L. boliviana have the basal portion of the metapostnotum slanting posteriorly, not vertical as in other species.

Key to species

(Females of L. boliviana not known)

1 Vestiture wholly black ........................................................................................................................... nigra

- Vestiture, at least on head and thorax, yellowish brown to whitish..............................................................2

2 Tegula yellowish, translucent; alary sclerites easily seen through tegula. Vertex of head much elevated behind ocelli, distance from median ocellus to vertex in frontal view as long as 1.4–1.6 MOD. Prepygidial and pygidial fimbriae of female orange. Apex of T7 of male forming two small lobes ( Fig. 9) .... separata

- Tegula brown to black, scarcely translucent. Vertex of head moderately elevated behind ocelli, distance from median ocellus to vertex in frontal view as long as 0.6–1.1 MOD. Prepygidial and pygidial fimbriae of female yellowish to dark brown. Apex of T7 of male forming two points ( Figs. 3–8)...........................3 3 Females .........................................................................................................................................................4

- Males.............................................................................................................................................................7

4 T2–T4 with erect, long hairs basad of apical band, up to 1.2–1.5 times MOD (without short, appressed hairs usual in other species). Face hirsute, hairs on clypeus as long as those between antennal sockets....... ......................................................................................................................................................... hirsutula

- T2–T4 with two strata of hairs basad of apical band: one usually of appressed hairs (short, at most 0.8 times MOD), and another of sparse, erect hairs (0.5–1.0 times MOD). Hairs on clypeus shorter than those between antennal sockets..............................................................................................................................5

5 Smaller species, 4.5–5.0 mm long. Metapostnotum with short basal portion slanting posteriorly, then vertical ..................................................................................................................................................... minima

- Larger species, 6.0– 7.2 mm long. Metapostnotum nearly vertical, slightly convex....................................6

6 T2–T5 with black hairs basad of apical band. Scutellum, close to scutum, with distinct, scattered punctures bearing hairs ........................................................................................................................... tucumana

- T2 with pale hairs basad of apical band; T3–T5 variable (hairs pale in specimens of northern distribution, but dark in specimens from southern Mendoza, Neuquén and Río Negro). Scutellum with bare basal band, although few minute punctures may be present ............................................................................. monteana

7 Smaller species, 4.7–5.2 mm long. Apex of T7 forming two short points ( Fig. 8). Metapostnotum with short basal portion slanting posteriorly, then vertical ......................................................................... minima

- Larger species, 5.5–7.0 mm long. Apex of T7 ending in two long points ( Figs. 3–7). Metapostnotum variable................................................................................................................................................................8

8 Tibial spurs of mid and hind legs dark brown. T2–T4 with only appressed hairs basad of apical band. Metapostnotum with short basal portion slanting posteriorly, then vertical ................................... boliviana

- Tibial spurs of mid and hind legs yellowish. T2–T4 with erect hairs or intermixed erect and appressed hairs basad of apical band. Metapostnotum nearly vertical..........................................................................9

9 T2–T4 with long hairs basad of apical band, those on T2 up to 2.8 times MOD. Apex of T7 with points separated by notch with straight base ( Fig. 5) ................................................................................. hirsutula

- T2–T4 with short hairs basad of apical band, those on T2 at most 1.2 times MOD. Apex of T7 with points forming a rounded or V-shaped notch between them.................................................................................10

10 T2 with pale hairs basad of apical band. Pubescence of basitarsi sparse, cuticle readily visible below hairs. Apex of T7 with points forming a V-shaped notch between them ( Fig. 6) .................................... monteana

- T2 with dark hairs basad of apical band Pubescence of basitarsi dense, hiding underlying cuticle. Apex of T7 with points forming a U-shaped notch between them ( Fig. 3)................................................. tucumana

Figures

FIGURES 1 – 2. Leptometriella separata, female: 1, labrum (c, preapical carina with median denticle), scale line = 0.1 mm; 2, posterior view of mesosoma (mtp, metapostnotum; b, bare basal band), scale line = 0.2 mm.

FIGURES 14 – 21. Leptometriella hirsutula, male: 14, genital capsule, ventral (left) and dorsal (right) views; 15, S 7, ventral view showing vestiture; 16, S 7, dorsal view; 17, S 8, ventral view. L. separata, male: 18, genital capsule, ventral (left) and dorsal (right) views; 19, S 7, ventral view showing vestiture; 20, S 7, dorsal view; 21, S 8, ventral view. Scale lines = 0.1 mm.

FIGURES 22 – 25. Leptometriella monteana, male: 22, genital capsule, ventral (left) and dorsal (right) views; 23, S 7, ventral view showing vestiture; 24, S 7, dorsal view; 25, S 8, ventral view. Scale lines = 0.1 mm.