Calliopsis zebrata, BOBBAE

Rozen, Jerome G., 2008, The Solitary Bee Calliopsis zebrata: Biological and Distributional Notes and Description of Its Larva (Hymenoptera: Andrenidae: Panurginae), American Museum Novitates 3632 (1), pp. 1-12 : 3-6

RE- DESCRIPTION OF ADULTS OF CALLIOPSIS ZEBRATA BOBBAE

Figures 1–3

The large sample of adults of Calliopsis z. bobbae from Flagstaff permits a more complete understanding of the range of color pattern than presented by Rozen (1958). In the following re-description, the most diagnostic characters are in boldface, whereby members of this population can be distinguished from those currently assigned to C. z. zebrata . Parenthetical remarks refer to C. z. zebrata .

MALE: Outer (anterior) surface of scape with broad yellow stripe (stripe tending to be narrower); pedicel with or without yellow spot on outer surface (pedicel without yellow spot); first flagellomere with conspicuous yellow outer surface concolorous with that of scape (often surface only as pale as following flagellomeres). Lateral angles of pronotum each with large yellow maculation (maculation smaller to absent); lateral pronotal lobes each with small to large yellow maculation (usually dark). Mesoscutum (as in fig. 1) usually with small to large yellow maculation, sometimes covering entire sclerite (invariably dark); metanotum (as in fig. 1) often with yellow maculation (invariably dark). Tegula with yellow maculation (often without yellow maculation). Legs with extensive yellow maculations, so that middle and hind femora each with yellow ventral stripe extending to, or almost to, base (yellow maculations more or less reduced, so that middle and hind femora with yellow restricted to apices); anterior surface of hind tibia yellow (sometimes with large dark area occupying middle of surface). Dorsal metasomal bands broad, never interrupted sublaterally (often narrow, sometimes so narrow that sublateral dark spots interrupt band on first segment); second (occasionally also third) metasomal sternum (fig. 2) with small to very small, often irregularly shaped yellow lateral spot on each side (spots absent except in Oklahoma males).

FEMALE: Scape with narrow yellow stripe on outer surface to completely dark (completely dark). Subantennal areas light (sometimes dark); clypeus completely yellow except for pair of transparent brownish spots characteristic of both sexes (with pigmented, variablesized, opaque dark maculations [fig. 3], which darken center of clypeus beneath supraclypeal area on some specimens). Lateral pronotal angles, each with large yellow maculation (maculation reduced to absent); lateral pronotal lobes yellow or at least with yellow spot (usually dark). Tegula with anterior yellow maculation (usually dark, without yellow). Mesoscutellum (fig. 1) usually with small to large yellow maculation, sometimes covering entire sclerite (invariably dark); metanotum (fig. 1) sometimes with median maculation (invariably dark). Legs with more extensive yellow maculations so that dorsal surface of midtibia mostly yellow (less extensive yellow maculations, so that dorsal surface of midtibia occasionally primarily dark). Dorsal metasomal yellow bands wide, so that lateral parts of band of tergum 5 fused or at least contiguous (often separated medially).

MATERIAL EXAMINED: 4 males, USA: AZ: Coconino Co.: Flagstaff , N35 ° 11 9 9 0, W111 ° 39 9 4 0, 6971 ft, VIII-13-2007 (M.A., K.C., J.G. Rozen); 32 males, 10 females, same except VIII-14-2007 (M.A., J.G. Rozen); 7 males, 14 females, same except VIII-30-2007 (J.G. Rozen); 2 males, same except VIII-7–9-1959 (K.V. Krombein); 1 male, same except Mormon Lake , 7000 ft, VII-8–15- 1956 (F.G. Werner) Astragalus humistratus .

REMARKS: As noted earlier ( Rozen, 1958), C. zebrata exhibits considerable geographic variation in color pattern, and C. z. bobbae has the most extensive pale markings of all samples found to date. However, the variability of C. z. zebrata as now defined deserves further analysis based upon more extensive collections so that we can understand the range of variation of its populations. The sample of eight males and six females collected by Michener in Oklahoma is a case in point. Although the females have dark clypeal pigmentation and reduced yellow markings on their pronotal angles and legs, their tegulae are yellow at the base and one has a small yellow mark on its pronotal lobes. Furthermore, males have rather extensive yellow on their pronotal lateral angles and lobes and yellow lateral spots on their metasomal sternum 2, as do males of C. z. bobbae. None of the individuals display yellow on their mesoscutellum or metanotum. Obviously the sample comes from the eastern edge of the species range whereas C. z. bobbae is from the extreme western edge of the range despite the males’ sharing these features in common. After a broad analysis of the geographic variation is conducted, we will have a better understanding of the nature and distribution of this variation and can determine whether it is reasonable to recognize the two subspecies. Also, as one reviewer pointed out, DNA data might be desirable here for delineating species, subspecies, and population boundaries.

BIOLOGY OF CALLIOPSIS ZEBRATA BOBBAE

Figures 4–7

MATING: Margaret first observed males of this species flying swiftly close to the ground in an area soon discovered to be the nesting site. She also saw several individuals (presumably females) as they descended into burrows. When I picked up a specimen, I was able to identify the species because of its yellow mesoscutellum. On our return the following day, we observed the extensive activity of numerous males flying close to the ground and many mating encounters of males and females tumbling on the ground, usually with a number of males attempting to copulate with a single female. We often collected mating pairs with our fingers. When I returned to the site on August 30, 2007 (16 days later), females were still nesting, and males, though less common than earlier, were still looking for mates. Although mating occurs at the nesting site, the area was also supplied with scattered host plants that females occasionally visited. Thus, one cannot make a distinction between mating at the nesting site as opposed to mating at the flowers. No couples were observed flying in copula.

Cockerell’s (1915) description of the swift flight of male C. z. zebrata was almost certainly mating behavior because it is identical to our observations of the mating of C. z. bobbae. Rozen’s (1958) accounts of the matings of C. anthidia and C. micheneri agree completely with that of C. z. bobbae. Thus it would not be surprising if mating of all Macronomadopsis species were similar. This behavior differs from what is known about the species of the subgenus Nomadopsis , most species of which are known to fly in copula rather to initiate brief mating bouts while tumbling over the ground ( Rozen, 1958).

DESCRIPTION OF NEST: The nesting site of Calliopsis z. bobbae consisted of scattered nests in a horizontal area of sparse, low vegetation exposed to the sun most of the day through a partly open canopy of tall trees (fig. 4). The bees generally excavated nests in the bare spots between the plants (fig. 5). The plants were grasses and the decumbent host plant that was widely scattered throughout the area. The site was at least 6 m in diameter, but its exact shape and size were uncertain because of daily showers that obscured nest entrances from day to day and because some of the entrances were in surrounding, more vegetated areas. This site was not unusual compared with the nesting sites of other Macronomadopsis that I have studied, except I cannot remember a site where the host plant was widely dispersed among the nest entrances. The soil was sandy, without large rocks, and moist because of the showers.

Nest entrances were surrounded by fresh tumuli resulting from females’ having to dig out tunnels filled with soil from the rain of the previous day on each of our three study visits. Main tunnels descended more or less vertically; one measured 5.5 mm in diameter. Cells, ranging in depth 5.5– 11 cm, were subhorizontal with the front end slightly higher than the rear. They were arranged singly (i.e., not in linear series), each connected to the main tunnel by a moderately short, soil-filled lateral. Thus, nest architecture was essentially the same as that diagrammed by Rozen (1958: fig. 63) for Calliopsis a. anthidia .

Cell closures, 4.5 mm in diameter on the inside, were a somewhat concave spiral of four coils to the radius. Cells were approximately 7.5 mm in maximum diameter and 13 mm long. The cell walls were slightly smoother and shinier in the rear than in the front, although the linings at best were faint. When tested with a water droplet, the surface was waterretardant. Feces in cells containing hibernating larvae were placed at the rear of the cell, as typical for all known Calliopsis . Vacated cells were backfilled by the newly departing inhabitant. The presence of such cells indicates that the site had been used by the previous generation. In general there were no features of the nest that could distinguish it from that of related species.

Hicks’s (1936) report on the nesting biology of Calliopsis z. zebrata , though lacking in some comparable details, is entirely consistent with that of C. z. bobbae.

PROVISIONING: Females of Calliopsis z. zebrata transport pollen as a moist mass surrounding their hind tibiae. The pollen of Astragalus humistratus has a brown tinge, a color that is also imparted to the spherically shaped, completed provisions. Two food spheres were 3.8 and 4.3 mm in diameter, and, like those of other known species of Calliopsis , they are coated with a shiny, clear, waterproof coating (fig. 7).

TEMPORAL DISTRIBUTION: The reported temporal flight range for Calliopsis zebrata is June 3 to August 23 ( Rozen, 1958). Michener found the nesting site of Calliopsis z. zebrata on May 18, 1977. The Flagstaff site of C. z. bobbae was discovered and visited on August 13 and 14, 2007, and revisited on August 30, 2007, when the nests were excavated. There is no evidence that this species or any other species of Macronomadopsis has more then one generation per year. Because adult populations of bees generally are active for a month or so, local populations may be synchronized with the availability of their pollen plants and, in turn, to climatic conditions that support flowering. Such temporal as well as geographic isolation of populations of a species may promote endemism and the development of distinct color patterns among conspecific populations, as seems to be the case here.

Hicks’s (1936) observations of even earlier emergences of adults of Calliopsis z. zebrata were based on larvae collected in wintertime and retained ‘‘at slightly above room temperature’’ in the laboratory before they emerged.

CLEPTOPARASITISM: A single female of Triepeolus pectoralis (Robertson) ( Apidae : Nomadinae). ( Apidae , Nomadinae) was observed while I excavated nests on August 30, 2007. Since it was not searching the ground for nest entrances, it was probably not a cleptoparasite of this species. According to Rightmyer (2006), it has been reported to attack nests of Melissodes druriella (Kirby) (Apidae) . No cleptoparasitic larvae were found in brood cells. Of known Oreopasites ( Apidae : Nomadinae), a genus associated with many species of Calliopsis , only O. vanduzeei Cockerell is a confirmed parasite of any Macronomadopsis; its single host species is C. anthidia ( Rozen, 1992) .

Figures

Figs. 1–3. 1–2. Macrophotograph of adult Calliopsis zebrata bobbae from Flagstaff, Arizona. 1. Dorsum of female, showing well-developed yellow maculations on mesoscutellum and metanotum. 2. Male metasomal showing paired yellow spots (leaders) on metasomal sternum 2. 3. Face of adult female of C. z. zebrata from Oklahoma showing dark clypeal marks, which on other specimens from same locality can be less or more extensive.

Figs. 4–7. 4. Margaret collecting mating pairs of Calliopsis zebrata bobbae by hand at nesting site, the more-or-less barren surface in the foreground. 5. Close-up of nesting surface, with lower leaders pointing to some (among many) nest tumuli and upper leaders pointing to some (among many) food plants. 6. Close-up of flowering Astragalus humistratus. 7. Provision sphere.