Succinapis proboscidea, Engel, 2001

ENGEL, MICHAEL S., 2001, A Monograph Of The Baltic Amber Bees And Evolution Of The Apoidea (Hymenoptera), Bulletin of the American Museum of Natural History 2001 (259), pp. 1-1 : 1-

Succinapis proboscidea , new species Figures 96–98 Plate 7b

DIAGNOSIS: This is the most distinctive of all the Succinapis species. The grossly enlarged clypeal protrusion that is both bent anteriorly as well as extending above the level of the antennae by more than the diameter of an antennal socket (figs. 96–98) serves to immediately differentiate S. proboscidea from both S. micheneri and S. goeleti .

DESCRIPTION: Female. Total body length 4.15 mm; forewing length 3.55 mm. Head wider than long (length 1.34 mm, width 1.43 mm). Clypeal protrusion greatly enlarged, extending above level of antennal sockets by more than diameter of an antennal socket, protrusion bent anteriorly (figs. 96–98). Upper interorbital distance 0.98 mm; lower interorbital distance 0.93 mm. Interocellar distance 0.40 mm; ocellocular distance 0.30 mm; median to lateral ocellus 0.10 mm. Intertegular distance 0.98 mm. Basal vein basad cu­a by vein width; 1m­cu bisecting second submarginal cell; 2rs­m distad 2m­cu by two times vein width; first submarginal cell shorter than second and third combined; length of anterior border of second submarginal cell one­fourth that of posterior border; length of posterior border of third submarginal cell 1.75 times that of anterior border, anterior border two times length of that of second submarginal cell; six distal hamuli, arranged in a single, evenly spaced series.

Clypeus with sparse, minute punctures, integument between smooth; anterior­facing surface of clypeal protrusion with a few weak longitudinal striae. Scape with minute punctures separated by a puncture width, integument between smooth. Face with minute punctures separated by 1–2 times a puncture width, integument between smooth; punc­ tures becoming gradually more faint and more sparse toward vertex and on gena. Pronotum with minute punctures separated by a puncture width except medially punctures faint, integument between smooth. Mesoscutum mostly obscured by a thin layer of Schimmel; where evident, integument with faint, minute punctures separated by 1–2 times a puncture width, integument between smooth. Scutellum sculptured as on mesoscutum. Tegula with minute, faint punctures on outer half, otherwise integument smooth. Metanotum obscured from view by fracture planes and flows from scutellum. Pleura with small punctures separated by 1–2 times a puncture width, becoming faint on central disc of mesepisternum and separated by 2–4 times a puncture width, and hypoepimeral area with faint and exceedingly sparse punctures, integument of pleura smooth between punctures. Propodeal lateral surface with minute, faint punctures separated by 2–3 times a puncture width, integument between smooth; basal area of propodeum glabrous. Metasoma faintly imbricate and impunctate.

Color, where evident, dark brown, without maculations. Wing membrane hyaline; veins strong and dark brown.

Pubescence generally whitish. Labrum with moderate­length, simple, erect setae widely scattered over surface. Clypeus with minute, suberect, simple setae restricted to lateral borders and short, simple, suberect, anteriorly­directed setae on dorsal­facing surface of clypeal protrusion. Face with sparse, suberect, minute, simple setae, such setae becoming slightly more dense in lower paraocular area near clypeal lateral border. Setae of vertex and gena as described for face. Postgena with short, simple, erect setae. Pubescence of pronotum as described for face except setae of dorsal surface restricted to posterior border. Mesoscutum with short, sparse, simple, erect setae evident through thin layer of Schimmel. Scutellum with erect, long (1–3 OD) setae on posterior third, setae each with several minute branches. Hypoepimeral area without setae; remainder of pleura with pubescence as described for face. Lateral surface of propodeum with pubescence as described for face; basal area of propodeum without setae. Inner surface of metafemur and metatrochanter without pubes­

97. Oblique, lateral view. 98. Dorsal view. Scale bar = 0.5 mm.

cence except apical quarter of metafemur with dense field of keirotrichiae; inner surface of metatibia with keirotrichiate zone; corbicula bordered by long, minutely­plumose setae; metatarsus with simple, stout setae; six comb rows on inner surface of metabasitarsus. Metasomal terga with scattered, simple, short, appressed setae, sparse on central discs; sterna with scattered, simple, erect, slightly fuscous setae.

MATERIAL: Three specimens. Holotype. Female, worker caste, B­JH 96 ( AMNH) labeled: ‘‘Baltic amber: Eocene, Kaliningrad, Yantarny’’ // ‘‘ Holotype, Succinapis proboscidea Engel’’.

Paratype. Female, worker caste, B­JH 99 ( AMNH) labeled: ‘‘Baltic amber: Eocene, Kaliningrad, Yantarny’’ // ‘‘ Paratype, Succinapis proboscidea Engel’’.

Paratype. Female, worker caste, Nr. 10 (CSUL) labeled: ‘‘ Paratype, Succinapis proboscidea Engel’’.

ETYMOLOGY: The specific epithet is derived from the Greek word proboskidos, referring to the trunk of an elephant, and is a reference to the structure of the large clypeal protrusion of this species.

Internal Phylogeny of Succinapis

The morphology of the clypeal protrusion suggests a hierarchy of relationship among the species of Succinapis (fig. 99). By comparison to other melikertine genera as outgroups it is possible to build a preliminary cladistic hypothesis for the three known Succinapis species. The presence of the clypeal protrusion is a unique apomorphy among the corbiculate Apinae and nicely serves to support the monophyly of the genus. The polarity of the different morphotypes of clypeal protrusions is impossible to determine in isolation from other characters as there is no corresponding structure in the outgroups. The apically bent clypeal protrusions of S. micheneri and S. proboscidea could be interpreted as plesiomorphic with S. goeleti and S. micheneri perhaps clustered on the basis of shortened protrusion and S. goeleti autapomorphic for a straight process, or if the polarity of the protrusion’s size is removed, then our three­taxon statement collapses to a trichotomy. The same scenario of difficulties applies if the polarities are reversed for each of the discussed characters. Fortunately, the sculpturing of the mesepisternum provides some information that can be compared to the related melikertine genera and for polarizing the species in Succinapis . The mesepisternum in all species of Melikertes is smooth and impunctate. Within Succinapis smooth pleural integument is only found in S. goeleti , while both S. micheneri and S. proboscidea have punctured mesepisterna. It would therefore appear that S. goeleti is the most plesiomorphic species of the genus by comparison to Melikertes . This hierarchy polarizes the clypeal protrusion morphology (fig. 99). The shortened clypeal protrusion that does not project more than an antennal socket diameter above the antennal sockets observed in S. goeleti and S. micheneri is presumably plesiomorphic. The apical bend of the clypeal protrusion is an apomorphic feature uniting S. micheneri and S. proboscidea , while the greatly enlarged process is an autapomorphy of S. proboscidea (fig. 99).

Genus Melikertes Engel , status novus

Electrapis ( Melikertes ) Engel, 1998a: 95. Type species: Electrapis (Melikertes) stilbonota Engel, 1998 a, original designation.

DIAGNOSIS: This genus is similar to Succinapis but lacks the basal clypeal protrusion.

DESCRIPTION: Malar space short, shorter than basal mandibular width. Epistomal sulcus forming obtuse angle or nearly linear (e.g., M. stilbonotus : fig. 100); clypeus without basal clypeal protrusion (fig. 100). F1 longer than F2; F2 equal to F3. Inner margins of compound eyes roughly parallel. Preoccipital ridge rounded or weakly carinate. Mesoscutal anterior border broadly rounded; tegula tear­drop shaped; scutellum not bulging, not projecting over metanotum (fig. 101). Basal area of propodeum nearly horizontal, not declivitous. Keirotrichiate field not elevated (fig. 102); metatibial spur serrate or minutely ciliate; auricular basket sparse, setae short; rastellum strong and formed of stiff setae (fig. 102); metabasitarsus parallelsided (fig. 102). Three submarginal cells (fig. 103). Metasomal terga not banded.

COMMENTS: I previously (Engel, 1998a) erroneously reported an absence of metatibial

124 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 259

spurs for Melikertes . Subsequent study of the type material for M. stilbonotus as well as newly discovered material of other melikertine bees has revealed a single, reduced metatibial spur. This structure is difficult to observe in the holotype and paratype of M. stilbonotus but is distinctly present (fig. 102).

Figures

Figs. 96–98. Head of holotype female of Succinapis proboscidea, new species. 96. Frontal view.