Ptiloglossa tarsata (Friese, 1900)

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 : 66-67

Ptiloglossa tarsata (Friese, 1900)

Locality and nesting site.

The observations on the biology and nest structure were carried out during January 25th-30th; March 10th-16th, 2011; and January 4th-14th, 2012 at Paraje La Florida (25°0.817'S, 65°33.534'W), Salta province, Argentina. Two nests were excavated at this locality, which is in a transitional habitat between rain and dry forest with a MAT around 17 C° and a MAP between 700 to 800 mm ( Baudino 1995). Two nests were found in a formerly plowed area in the surroundings of the establishment "La Florida". The soil surface was flat and the cover was composed mostly of grasses and plants of Solanum sp. and Clematis sp. ( Fig. 8 ). The soil consisted of clayish to silty material and was devoid of rocks. The first nest was located next to a fence below a Solanum sp. plant, whereas the entrance of the second nest was partially covered by grasses.

Daily activity.

The foraging activity started about 07:00 am, with full daylight, when females were observed visiting flowers of Solanum sp. ( Fig. 9 ). One female made successive foraging trips, remaining inside the nest around 10 minutes after each trip. Foraging trips lasted around 20 minutes. This activity continued until 02:00 pm when the female closed the entrance from inside. The females were inside the main tunnels when the nests were excavated.

Description of nests.

The entrance of the first nest, circular and 1 cm in diameter, was located at the center of a tumulus, 5.8 cm in maximum diameter and 4 cm high. The tumulus was composed of unconsolidated soil ( Fig. 10 ). The main tunnel, vertical and slightly sinuous, was 40-61 cm long, and 1 cm in maximum diameter ( Fig. 11 ). The inner surface of the main tunnel showed horizontal and densely grouped scratches 1-3 cm long and 0.2 cm wide. These scratches were probably made by the female mandibles ( Fig. 12 ). The cells (n: 12), found at depths of 37-44 cm, were vertical and disposed radially around the main tunnel. Open cells were connected to the main tunnel by horizontal laterals, 5-7 cm long. Laterals ended in a raised, curved, entrance tunnel connecting with the vertical portion of the cell ( Figs 11, 13c and 19 ). Once lined and sealed, the distal part of the entrance tunnel became the curved neck of the cell ( Fig. 13b ). Each lateral tunnel ended in one or two entrance tunnels connected with cells occurring at the same depth ( Fig. 19 ). Entrance tunnels connected to closed cells were filled with soil ( Fig. 19 ). The vertical portion of a cell was 1.9-2.0 cm long and 0.9-1 cm in maximum diameter (n: 12). The neck was 0.6-0.8 cm in diameter (n: 12). The inner walls of the cells and the neck were smooth and lined with a whitish, semitransparent cellophane-like material that extended up to the closure ( Fig. 14 ). The cell closure, made with soil material, showed a spiral pattern composed of three coils on the inside ( Fig. 15 ). Some cells contained a white wad of cotton-like material. The first nest excavated contained nine cells: three with eggs, three with young larvae, two with mature larvae, and one unfinished empty cell ( Fig. 19 ). The second nest contained four cells, each with an egg. The eggs were whitish, cylindrical and lightly curved, 3 mm long and 0.8 mm wide. They lay on top of the semiliquid provisions ( Fig. 20 ). Young larvae were also whitish, curved, and almost completely submerged in the provisions. Full grown larvae, more yellowish, were found inside cocoons made of a brown, thin, translucent, and slightly coriaceous material. The cocoon operculum is located at the base of the curved neck and consists of a circular disk of translucent, amber, semi-rigid material ( Fig. 16 ). Below the operculum were two more disks of similar structure and composition to it. SEM observations indicated that these three disks were woven structures composed of crossed, coalescent silk threads of different thickness that leave small circular holes of 0.14-0.15 mm in diameter among them ( Figs 17 and 18 ).

Figures

Figures 8 - 18. Ptiloglossa tarsata (Friese, 1900). 8 General view of the nesting site at " La Florida " (Salta province), the arrow indicates the location of the nest; 9 Female of Ptiloglossa tarsata foraging in a flower of Solanum sp. 10 Tumulus of unconsolidated soil, scale line: 1 cm 11 General view showing the nest architecture with a cell at the end of the main tunnel 12 Group of scratches probably produced by female's mandibles. The arrow indicates their location in the main tunne; 13 (a) cell with cellophane-like lining and provisions, (b) neck and (c) entrance tunnel, scale line: 1 cm 14 One cell showing the cellophane-like lining on the wall, scale line: 1 cm 15 Spiral closure of one cell, scale line: 0.5 cm 16 Cocoon operculum with holes, scale line: 0.5 cm 17 Scanning electron micrograph of the cocoon operculum showing the fabric of silk threads with small circular holes, scale: 500 µm 18 Onecircular hole surrounded by silk threads, scale: 50 µm.

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.