Anthophorula

Rozen, Jerome G., 2011, Immatures of Exomalopsine Bees with Notes on Nesting Biology and a Tribal Key to Mature Larvae of Noncorbiculate, Nonparasitic Apinae (Hymenoptera: Apidae), American Museum Novitates 2011 (3726), pp. 1-52 : 29-30

ANTHOPHORULA (ISOMALOPSIS) UNCICORNIS VAQUERO AND ROIG

Table 2

I found four nests of Anthophorula uncicornis with their entrances grouped near one another (two were 13 cm apart) on the horizontal ground surface at Basilio Nievas, San Juan Prov., Argentina, on November 10, 1998, where Eremapis parvula and also an unknown eucerine (probably Canophorula) also actively nested in the fine soil, which was dry on the surface but moist below. The area was partly surrounded by Prosopis trees. Anthophorula uncicornis appeared to be in the early stages of nesting activity since numerous eggs and small larvae were observed, but almost no late-stage larvae were detected. Since vacated cells from early populations were uncovered, the site obviously had been used previously.

NEST ARCHITECTURE: Three nests of Anthophorula uncicornis contained 5, 8, and 14 females, respectively. Two excavated nests revealed in each an open main tunnel descending vertically, one to a depth of 25 cm and the other to 17 cm at which points they gave rise to numerous side tunnels. One of five (or six) cells associated with the first nest was uncovered at a depth of 35 cm. Main burrows tended to be wider (i.e., 3.5 mm in diameter) near the surface and narrower (2.8 mm in diameter) where the soil was moist .

Cells were oriented with their rear end much lower than the front (see table 2). Ovoid in general shape, their upper surface was longer and more curved while their lower surface was flatter when viewed from the side, and the region of greatest diameter was approximately onethird of the cell length from the posterior end. The inside closure diameter of 2.7 mm (N = 2). At the posterior end the cell surface was very smooth and reflective where the provision loaf was attached and, when tested with a water droplet, highly nonabsorbent. (In four cells preserved in the collection, the point of provisions attachment is marked by a small spot of provisions in the middle of the reflective surface, proof of regular attachment of provisions to the cell’s rear end.) The reflective area is restricted just to this area. Where the surface dulls it becomes somewhat more water absorbent when tested, 4 and the surface itself is not as smooth. At the front end of the cell, the surface becomes even more uneven, though not as much as the wall of the lateral. All cells, old or fresh, were found singly, far from one another. Cell closures were deeply concave spirals of four distinct coils to the radius, and laterals were soil filled. 5

4 For testing the waterproof qualities of cell walls, I have found that a small-bore hypodermic syringe is an excellent tool for delivering a small droplet to the surface of small cells. Because different parts of cell walls may repel droplets differentially, small drops can be applied to different parts of the same wall to detect variability.

5 A single cell of Anthophorula (Isomalopsis) macrodonata Vaquero and Roig ( Argentina: Tucaman Prov., 11 km N Cadillal, 12-03-1989 (A. Roig)) preserved in the AMNH collection had smooth walls and a closure similar to those of A. uncicornis except the closure was not as deeply concave; the rear end of the cell had not been preserved.

PROVISIONING AND DEVELOPMENT: Females of Anthophorula uncicornis shape mealymoist provisions into a loaflike mass described below. When viewed from the side or from above (figs. 47, 48), the front end is broadly rounded while the rear tapers to a terminal truncation where it attaches to the rear surface of the cell. As in A. chionura ( Rozen and MacNeill, 1957: figs. 1, 2), the front lower edge bears a ventral projection, i.e., a “foot,” and its top surface is curved in side view, as in A. chionura , unlike the flattop provisions of A. completa (fig. 45). The entire lower surface of the provisions including the foot is elevated (fig. 47) and does not touch the wall. The attachment of the provisions to the most nonabsorbent surface of the cell may function to prevent moisture loss without the female bee devoting effort or waterproofing agent to the entire cell surface. The female places her elongate, curved, white egg with a smooth chorion on the top surface of the provisions in the sagittal plane of the cell, no doubt with the egg’s anterior end pointing toward the closure. Because of its strong curvature, the egg touches the surface of the provisions only by its front and posterior ends, while the midsection arches upward.

Young larvae crawl over the provisions as they feed, but no observations were made that might reveal how larger larvae hold provisions as they feed. Last larval instars do not spin cocoons, as evidenced by their absence in cells of a previous generation and the lack of strongly projecting salivary lips on mature larvae. Fecal material in these cells is plastered against the wall mostly toward the rear.

PARASITISM: No cleptoparasites were associated with these nests.