Cadeguala albopilosa (Spinola, 1851)

Sarzetti, Laura C., Genise, Jorge F., Sanchez, M. Victoria, Farina, Juan L. & Molina, M. Alejandra, 2013, Nesting behavior and ecological preferences of five Diphaglossinae species (Hymenoptera, Apoidea, Colletidae) from Argentina and Chile, Journal of Hymenoptera Research 33, pp. 63-82 : 69-71

Cadeguala albopilosa (Spinola, 1851)

Locality and nesting site.

The observations were carried out during November, 4th, 2009 and February, 17th, 2011 at Bahia Mansa (43°7.467'S, 71°39.95'W), Parque Nacional Los Alerces, Chubut province, Argentina ( Fig. 30 ). On November, 9th, 2009 a nesting site was also found along the route 235 (43°26.142'S, 72°10.017'W), near Yelcho Lake, Palena province (Region de Los Lagos), Chile. The nests were studied at the xeric Austrocedrus forest of Bahia Mansa (Parque Nacional Los Alerces) with a MAT around 8 C° and MAP around 1200 mm. The nesting site at Bahia Mansa was slightly sloped and the soil subsurface contained a thin ash layer produced by the Chaiten eruption of May 2008 ( Figs 30 and 32 ). The soil cover was composed of grasses and short herbs ( Figs 30 and 31 ). The nests, around 20 and located among grasses, were distributed in an area of 5 × 7 m. The soil, containing many rocks, roots and grass rhizomes, was composed of silt to very fine sandy material. Nests of sweat bees, aestivation chambers of earthworms, and feeding chambers of cicadas were also present. The Chilean locality along route 235 was a disturbed forest clearing composed of a dense grass cover. The area had some slopes with large rocks and trunks over the surface. Around 12 nests were distributed in an area of 6 × 1.5 m almost horizontal and partially covered by grasses. At both localities, closest nests were separated each other by 2-4 cm.

Daily activity.

Beeswere observed removing soil from the nests during November, 4th 2009 from 09:00 am to 05:00 pm. In the second field trip, during February 2011, no activity was observed.

Description of nests.

Three nests were excavated during November 2009 when bees were active. The entrance, circular, 0.5 cm in maximum diameter was at the center of a large unconsolidated tumulus ( Fig. 31 ). It was composed of a mixture of soil material and ash, 3-3.5 cm in maximum diameter and 2.5 cm high. During February 2011, when no activity of bees was observed, a piece of soil from the nesting site was extracted and taken to the laboratory for examination with a tomograph. The tomographic images provided a more precise picture of the nests and cells ( Figs 35-37 ). The main tunnel, circular in cross section, was plugged with soil 2-3 cm below the entrance and descended vertically, straight or more sinuously among rocks ( Fig. 22 ). It was 18-20 cm long and 0.5 cm in maximum diameter. The cells, found at a depth of 18-20 cm, were vertical and connected to the main tunnel by lateral ones, which were 2.5-3 cm long and mainly horizontal or gently curved ( Fig. 23 ). They were filled with soil when connected to closed cells. At the distal end, lateral tunnels curved downwards, 90° or less, and were connected with the vertical portion of the cell. Once lined and sealed, the more distal curved part of the lateral tunnel connected to the cell became its curved neck ( Figs 33 and 34 ). Each lateral tunnel ended in one or two cells ocurring at the same depth ( Fig. 22 ). The number of cells per nest ranged from 2 to 4 in the studied nests (n: 4). The vertical portion of the cells was 1.3-1.6 cm long and 0.6-0.9 cm in maximum diameter (n: 12). The neck was 0.5 cm in diameter (n: 5). The inner walls of the cells and the neck were smooth and lined with a whitish semitransparent cellophane-like material. Cells studied on November contained eggs laying on the surface of the semiliquid provisions. The eggs whitish, cylindrical and slightly curved were 2 mm long and 0.7 mm wide. Cells studied on February contained white pupae inside their cocoons. The cocoons were composed of a brown, translucent, thin, and slightly coriaceous material. The cocoon operculum, located at the base of the curved neck, was composed of one translucent, amber, and semi-rigid circular disk, 5.0-5.5 mm in diameter (n: 2). This disk was a woven structure composed of crossed silk threads of different thickness that leave small circular holes. Below the operculum there was a net of silk threads loosely arranged, similar to the filter-like structure observed by Rozen (1984) in the cocoon of various species of Diphaglossinae . Beneath the filter-like structure there was another disk with a similar microstructure to the operculum, but dome-shaped. It was called the ceiling of the pupation chamber by Rozen (1984).

Figures

Figures 30 - 37. Cadeguala albopilosa (Spinola, 1851). 30 General view of the nest site at Bahia Mansa, Parque Nacional Los Alerces (Chubut province) 31 tumulusof unconsolidated soil 32 two main tunnels and longitudinal view of the soil containing a thin ash layer 33 a pair of cells with provisions, necks and lateral tunnels, scale line: 1 cm 34 remains of cells of other nest, scale line: 1 cm 35 - 36 tomography images of one block of soil containing Cadeguala albopilosa nests, arrows indicate cells 37 3 D-reconstruction of one nest and isolate cells.

Figures 19 - 23. 19 Nest architecture of Ptiloglossa tarsata (Friese, 1900). 20 Cell with provisions and egg, cell neck, spiral closure, and entrance tunnel of Ptiloglossa tarsata 21 Nest architecture of Ptiloglossa matutina (Schrottky, 1904) 22 Nest architecture of Cadeguala albopilosa (Spinola, 1851) 23 Cell with provisions and egg, cell neck, location of the cell closure and entrance tunnel of Cadeguala albopilosa.