Family Stenotritidae

This family comprises two Australian genera of moderate-sized to large, robust, euceriform, hairy bees (Fig. 362). Superficially, these bees closely resemble those of the American tribe Caupolicanini of the Diphaglossinae [although one stenotritid species, Cenocollees smaragdinus (Smith), is bright metallic green]. Unlike colletids, they have a well-developed tibial scopa and a reduced femoral scopa, and pollen is accordingly carried principally on the tibia, as shown by Houston (1984). The first flagellar segment is longer than the scape and petiolate (Fig. 36-1b). The glossa is short, thick, rounded, and lacks the preapi-cal fringe, glossal lobes, and glossal brush, although the brush is perhaps represented by a few, sometimes bifid, apical hairs that are longer than the other glossal hairs. The prementum lacks a depression or fovea on its posterior (lower) surface. The two subantennal sutures below each antennal socket meet above the clypeus and delimit a small, triangular subantennal area under the antenna. The facial fovea, broad and not sharply defined, is absent in males. The ocelli are low on the face, nearer to the an-tennal bases than to the posterior margin of the vertex. The episternal groove is absent below the scrobal groove. There are three sub marginal cells (Fig. 36-1a). The stigma is slender, slightly longer than the prestigma and of the same width (measured to the wing margin), and vein r arises near the apex, the margin within the marginal cell not convex; the wing membrane beyond the veins is papillate but also bears minute hairs. The prepygidial and pygidial fimbriae of the female are large and dense (Fig. 36-2).

The larva, characterized by Houston (1975b) and McGinley (1981), is not distinguishable at the family level from that of certain Colletinae.

Although stenotritids have often been placed in the Colletidae, McGinley's (1980) study emphasized their distinctness at the family level, and that conclusion was supported in a way by Alexander and Michener's (1995) phylogenetic investigation of S-T bees. As noted in Section 21, in this phylogenetic study the stenotritid (Cteno-colletei) fell in such diverse positions in different analyses that there was no basis for considering it closest to any one other bee group (see Fig. 20-1). My belief, notwithstanding, is that the stenotritids are either the basal branch, sister group to all other bees (Fig. 20-1b), or a group within or sister group to the Colletidae (Fig. 20-1c, d). Among characters in support of the colletid relationship are the lobes and reduced disc of S7 of the male Stenotritus (Fig. 36-1f) but not of Ctenocolletes (Fig. 36-1c). Similarity to the Melittidae, however, in the lack of a femoral or more basal scopa and lack of the episternal groove below the scrobal groove, should be considered. The lorum, as in various Andrenidae, especially Megandrena and Alocan-drena, forms a stronger proboscidial lobe (Fig. 33-4g) than is found in many Colletidae, but it is even stronger in some Colletinae (Fig. 33-4b).

Some of the characters of Stenotritidae are common features of various large, fast-flying bees. These include the reduced stigma, papillate distal parts of the wings, the largely vertical propodeal profile, and perhaps the long, petiolate first flagellar segment. It is partly such charac

Figure 36-1. Structures of Stenotritidae. a, Wings of Stenotrituspubescens (Smith); b, Antenna of Ctenocolletes nicholsoni (Cockerell), male; c-e, S7, S8, and genitalia of male of C. smaragdinus (Smith); f-h, S7, S8, and genitalia of male of S. pubescens (Smith). (For the genitalia and sterna, dorsal views are at the left.) From Michener, 1965b.

Figure 36-1. Structures of Stenotritidae. a, Wings of Stenotrituspubescens (Smith); b, Antenna of Ctenocolletes nicholsoni (Cockerell), male; c-e, S7, S8, and genitalia of male of C. smaragdinus (Smith); f-h, S7, S8, and genitalia of male of S. pubescens (Smith). (For the genitalia and sterna, dorsal views are at the left.) From Michener, 1965b.

ters that are responsible for the similarity of Stenotritidae to the Caupolicanini, and for the relationship between Stenotritidae and Oxaeinae indicated in some of the phy-logenetic analyses of Alexander and Michener (1995).

The two genera of Stenotritidae are similar to one another in most characters, although strikingly different in the form of S7 and S8 of the males.

Key to the Genera of the Stenotritidae

1. T7 of male usually with well-developed pygidial plate; S7 of male a transverse band sometimes broadened and produced apically at each side, leaving large median emar-

gination (Fig. 36-1c), with hairs on apical margin or projections; basal elevation of labrum of female undivided; inner hind tibial spur of female thickest at basal one-

fourth to one-half, with long, coarse teeth Ctenocolletes

—. T7 ofmale with bare area representing pygidial plate but not defined by carinae; S7 of male with disc greatly reduced, connecting long laterobasal apodemes and a pair of hairy apical lobes (Fig. 36-1f); basal elevated area of labrum offemale binodulose; inner hind tibial spur offe-male tapering from base, with moderate-sized to coarse teeth Stenotritus

Genus Ctenocolletes Cockerell

Stenotritus (Ctenocolletes) Cockerell, 1929c: 358. Type species: Stenotritus nicholsoni Cockerell, 1929, monobasic.

Ctenocolletes is composed of large (14.0-20.5 mm long), euceriform, hairy, fast-flying bees (Fig. 36-2). They differ not only from Stenotritus but also from most other bees in (1) the broad, platelike or bandlike disc of S7 of the male, bearing short lateral apodemes and an entire to bilobed apical margin (Fig. 36-1c), and (2) the large S8 of the male, which has a short or slender apical process (Fig. 36-1d) and hairs on the apical one-third to one-half of the sternum, which is often exposed. On the basis of these sternal characters, Ctenocolletes could be regarded as the most primitive of bees, since S7 and S8 are more like the other sterna than like the totally different S7 and S8 found in most other bees. Supporting this view are the simple, articulated, hairy male gonostyli (Fig. 36-1e) and the well-formed male pygidial plate (except in C. ful-vescens Houston). But Ctenocolletes is closely related to Stenotritus, which shares none of these features. It seems likely that regulatory factors lead S7 and S8 to develop more like ordinary sterna in Ctenocolletes. Clearly, bees

Figure 36-2. Ctenocolletes nicholsoni (Cockerell), female. From Goulet and Huber, 1993.

Figure 36-2. Ctenocolletes nicholsoni (Cockerell), female. From Goulet and Huber, 1993.

have genes for ordinary sterna; a regulatory change could lead to such sterna on segments 7 and 8 as well as on more anterior segments. Other bees with such ordinary-looking male S7 and S8 include the Oxaeinae (Andrenidae). In fact, the Oxaeinae have an even more platelike S8, without a spiculum. Other bees with a platelike S7 are Melitta (Melittidae) and Euherbstia and Orphana (An-dreninae). The very different larval as well as adult characters argue against any close relationship between Ctenocolletes and these andrenid and melittid taxa. Some species of Ctenocolletes have an extraordinarily small propodeal triangle (incorrectly emphasized as a generic character by Michener, 1965b). Three species lack arolia in females (Houston, 1983b). Many other structures, including male genitalia, were illustrated by Michener (1965b) and Houston (1983a, b).

Ctenocolletes, found in Western Australia and the westernmost part of South Australia, comprises ten species, as revised by Houston (1983a, b; 1985).

Nesting, mating, and floral biology are described by Houston (1984, 1987). The nests resemble those of Stenotritus in major features; sometimes the cells are inclined, and only the distal parts are varnished with a secreted material.

Genus Stenotritus Smith

Stenotritus Smith, 1853: 119. Type species: Stenotritus elegans

Smith, 1853, monobasic. Oestropsis Smith, 1868a: 253, not Brauer, 1868. Type species:

Oestropsis pubescens Smith, 1868, monobasic. Gastropsis Smith, 1868b: xxxix, replacement for Oestropsis

Smith, 1868. Type species: Oestropsis pubescens Smith, 1868, autobasic. Melitribus Rayment, 1930a: 217. Type species: Melitribus greavesi Rayment, 1930, by original designation. [Ray-ment (1930b: 61) subsequently and invalidly designated Gastropsis victoriae Cockerell, 1906, as the type species.]

Stenotritus is composed of moderate-sized (body length 12-15 mm), euceriform, hairy, fast-flying bees. The characters of the hidden sterna suggest those of most colletids, S7 having a reduced disc, long basolateral apodemes, and two hairy apical processes (Fig. 36-1f); and S8 having a strong spiculum and a strong, subtrun-cate, hairy apical process (Fig. 36-1g). Presumably, these features are plesiomorphic, but the lack of a male pygidial plate and the immovable fusion of the gonostyli to the gonocoxites (Fig. 36-1h) appear to be synapomorphies of Stenotritus. Male genitalia and hidden sterna were illustrated by Michener (1965b); see also Figure 36-1f-h.

Stenotritus is known from the east to the west coasts of Australia and north to southern Queensland, but not from the tropical north. There are eleven species.

Important papers on nesting and floral biology are by Houston (1975b) and Houston and Thorp (1984). The nests are burrows in the soil, with more or less horizontal branches at the bottom, each leading to one or perhaps two bilaterally symmetrical (i.e., with flattened floor), horizontal cells lined with a very thin, water-repellant, secreted film. The provisions in each cell consist of a flattened ovoid mass, sometimes surrounded by liquid. Larvae do not spin cocoons.

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