Hoplitis fertoni (Perez, 1891)

Bogusch, Petr, Hlavackova, Lucie, Petr, Libor & Bosch, Jordi, 2020, Nest structure, pollen utilization and parasites associated with two west-Mediterranean bees (Hymenoptera, Apiformes, Megachilidae) nesting in empty snail shells, Journal of Hymenoptera Research 76, pp. 113-125 : 113

Hoplitis fertoni

Nest structure.

We collected 35 gastropod shells with nests of H. fertoni in three of the 13 localities surveyed. All of the localities were situated in dry hilly region. All shells were found on the ground surface and were not hidden. The closing plug was made of soil of light-brownish or greyish colour (Fig. 1A ). In most nests (32) the closing plug was placed at the shell aperture. In the remaining three shells it was placed a few mm inside the shell. Several nests had a vestibular (empty) cell below the plug. The rest of the shell was filled with brood cells. Some nests had one or more empty intercalary cells. The brood cell walls were fully lined with soil and inter-cell partitions were double (Fig. 1D ). The brood cells were arranged longitudinally along the spire of the shell cavity but some nests had two or more cells arranged transversally close to the nest aperture. Brood cell partitions were 2-5 mm thick (mean 2.6 mm) and the closing plug 3,5-8 mm thick (mean 4.9 mm) (Fig. 1D ).

Shell choice.

The majority (26, 74.3%) of the nests were built in shells of Sphincterochila candidissima . Other snail species used were Eobania vermiculata (4, 11.4%), Cernuella sp. (3, 8.6%) and Otala lactea (1, 2.9%). The 35 nests collected contained 217 brood cells (mean ± SD: 6.2 ± 2.24; range: 2-10 brood cells per nest). The nests in S. candidissima shells contained 4-9 brood cells (mean 6.4, median 7), and those in E. vermiculata shells 5-10 brood cells (mean 5.8, median 6). Nests in the smaller Cernuella sp. shells contained fewer cells (range 2-3, mean 2.3, median 2).

Nest associates.

Altogether 58 (26.7%) brood cells contained dead, dry or mouldy contents. Of the remaining brood cells, 126 contained pupae or adults of H. fertoni , and 33 were parasitized (25.8% of brood cells containing live insects). The golden wasp Chrysura hybrida ( Chrysididae ) was the most common parasitoid (21 cells in 14 nests). Cells parasitized by C. hybrida were recognizable by the presence of a semi-transparent brownish cocoon with a whitish spot within the thicker brownish cocoon of H. fertoni . We also found five nests parasitized by the velvet ant Stenomutilla collaris (seven cells) and one nest by Stenomutilla hotentotta (one cell) ( Mutillidae ). Velvet ants pupated and became adults by late spring (late May - June). Stenomutilla cocoons were very similar to those of C. hybrida but harder and darker and did not have whitish marks. We also found three nests parasitized by the cuckoo bee Dioxys moesta ( Megachilidae ) (one cell per nest). The cocoons of this species were composed of a single whitish layer sparsely covered with dark brownish faecal particles. Pupation and adult eclosion occurred more or less at the same time as in H. fertoni . Finally, we found one nest with one cell parasitized by the bee-fly Anthrax aethiops ( Bombyliidae ). The structure of all nests is illustrated in Fig. 2 .

Pollen contents.

We analysed pollen samples (remnants of unconsumed provisions) from six nests from two localities (S35 and S37). All pollen grains identified were Lithodora fruticosa ( Boraginaceae ) (Fig. 3A ). During of March 2019 we repeatedly observed Hoplitis fertoni females collecting pollen only on flowers of this species in various localities.

Figures

Figure 1. Structure of Hoplitis fertoni (A, D) and Osmia ferruginea (B, C, E) nests A shell of Sphincterochila candidissima with nest of H. fertoni B shell of S. candidissima with nest of O. ferruginea C larva of O. ferruginea on pollen-nectar provision D nest structure of H. fertoni E nest structure of O. ferruginea. Photos and drawings by P. Bogusch.

Figure 2. Diagrams of nest structures of nests of Hoplitis fertoni (right) and Osmia ferruginea (left). The nests are identified by locality snail codes (Cern - Cernuella sp., Ever - Eobania vermiculata, Iber - Iberellus sp., Olac - Otala lactea, Scan - Sphincterochila candidissima, Tpis - Theba pisana. Each box represents one brood cell, starting with the innermost cell on the left. Colours represent the various species recorded. White boxes represent intercalary cells.

Figure 3. A Macrophotography of pollen of Lithodora fruticosa from a Hoplitis fertoni nest (locality S 35). Photo by L. Petr. B macrophotography of pollen from an Osmia ferruginea nest (locality S 7). Larger pollen grains are Thymus vulgaris; smaller grains are Cistus albidus. Photo by L. Petr.