Flower associations
At both study sites the females of Quartinia major were observed to visit only flowers of three different species from three genera of Asteroideae, a subfamily of the Asteraceae. This is in congruence with the flower visiting records published by Kohl (1898), Saunders (1905) and Bequaert (1940) that are also all for members of the Asteroideae. Moreover, the brood cell provisions contained nearly exclusively pollen from flowers of Asteroideae. These findings suggest that Q. major is broad oligolectic (sensu Müller and Kuhlmann 2008) with regard to its pollen source, using exclusively pollen of Asteroideae for brood cell provisioning but from more than one genus of Asteroideae. Association with Asteraceae seems to be widespread within Quartinia as 79 % of 14 Palaearctic species (Benoist 1929, Bequaert 1940, Carpenter 2003, Gusenleitner 1973, Gusenleitner 1990, Hohmann et al 1993, Morice 1900, Popov 1948, Saunders 1905) and 55 % of 42 Afrotropical species (summarized by Gess and Gess 2010) for which flower-visiting records are available have been recorded from this plant family. In the Palaearctic eight species have been exclusively recorded from Asteraceae. However, Q. major is the first Palaearctic species for which oligolecty has been demonstrated by pollen analysis from brood cell provisions. In the Afrotropical region ten species were exclusively recorded from Asteraceae (cf. Gess and Gess 2010), indicating specialization on this plant family as the single pollen source, even though the oligolectic use of pollen of Asteraceae for brood cell provisioning has been demonstrated solely for Quartinia vagepunctata von Schulthess (Gess and Gess 1992).
At locality I the brood cell provisions contained nearly exclusively pollen of the Aster-type suggesting that pollen was actively collected only from Pulicaria mauritanica. This is also supported by the fact that pollen uptake by females of Quartinia major was observed only at this plant. In contrast pollen from Cladanthus arabicus, which is of the Anthemis-type, was probably only included in the provisions as a result of passive contamination either due to pollen grains adhering to the exoskeleton of the female wasp during nectar visits to C. arabicus or due to pollen transfer from disc florets of C. arabicus to the capitula of P. mauritanica by other flower visitors. A preference for flowers of P. mauritanica over flowers of C. arabicus by Q. major females is also suggested by the results of the random transect walks since more than 85 % of the females were recorded from Pulicaria. However, since both investigated brood cells originated from the same nest, the presumed preference for taxa having pollen of the Aster-type over taxa possessing pollen of the Anthemis-type should be confirmed with larger sample sizes.
The distinct technique of Quartinia major females during pollen uptake from disc florets of Pulicaria mauritanica has not been reported before for any other pollen wasp or bee species. Other Quartinia species ingest pollen either directly from the anthers or they brush pollen with their fore legs from the anthers or the body surface towards the mouth where it is ingested (Gess 1996, Gess and Gess 2010, Mauss and Müller 2016, Mauss and Mauss 2016). Squeezing out pollen from the corolla of disc florets in the early male phase with the mouthparts probably enables the females of Q. major to remove the pollen efficiently before it becomes available for other flower visitors. In this context it is of note that during cell provisioning, probable combined pollen and nectar collection flights of the female of Q. major from nest CH lasted for only 16 min in the median which is at the lower end of the range observed for some other pollen wasp species (17.3 min in Celonites abbreviatus (Villers), Bellmann 1984; 41.9 min in Celonites fischeri Spinola, Mauss and Müller 2014; 31.5 min in Pseudomasaris phaceliae Rohwer, Neff and Hook 2007; 31.3 min in Pseudomasaris edwardsii (Cresson) Torchio 1970). The comparatively short duration of the potential provisioning flights of Q. major may be associated with the derived technique of pollen uptake in this species. This is supported by the fact that C. abbreviatus, that also performs comparatively short provisioning trips (cf. Bellmann 1984), also uses a highly derived method for pollen uptake (Schremmer 1959, Bellmann 1984, Müller 1996, Mauss 2006).
Female brood care
Quartinia major was found nesting in friable soil close to its main forage plant. This is similar to the nesting situation in Quartinia canariensis Blüthgen (Mauss and Müller 2016), the Afrotropical Quartinia vagepunctata (Gess and Gess 1992), nesting in a metre square area clear of plants that was surrounded by the forage plants, and Quartinia poecila von Schulthess (Gess and Gess 2010), nesting on the mound formed around the forage plant, a situation suspected by Gess and Gess (2010) to be common to some other Afrotropical species of Quartinia. Each nest of Q. major had its entrance to one side of a little stone, slightly embedded in the substrate, offering some protection to and a somewhat stable substrate for the burrow descending beneath it and which is identical with the nest location next to a stone or an earth clod, recorded for Q. vagepunctata (Gess and Gess 1992) whereas the nests of other species were found on bare ground (Gess 2009, Gess and Gess 2010, Mauss and Müller 2016) and those of seven species in sand-filled snail shells (Gess and Gess 1999, Gess and Gess 2008).
The walls of the burrow and the newly provisioned cells of Quartinia major were non-rigid soil particle and silk structures with a silk lining, the silk being produced by the nest building female. This character occurs in all Quartinia species for which nesting is known (Gess and Gess 1992, 1999, Gess and Gess 2010, Mauss and Müller 2016) and is unique among the Masarinae (Gess and Gess 1992, Mauss 2007). Therefore it can be regarded as an outstanding apomorphic trait of Quartinia that enabled the members of the stem-line of Quartinia to inhabit ecosystems with friable, sandy soil (Mauss and Müller 2016).
A short more or less vertical turret surmounting the nest entrance as in Quartinia major is also present in nests of Q. canariensis (Mauss and Müller 2016) and most Afrotropical Quartinia species (Gess and Gess 2010). The existence of a turret at the nest entrance is probably a plesiomorphic trait of Quartinia adopted from the ground pattern of the Masarinae (Mauss 2007). A probably derived turret form exists in Q. vagepunctata that builds a horizontal, bag-like turret (Gess and Gess 1992).
As in Quartinia canariensis (Mauss and Müller 2016) there is no evidence that females of Q. major are able to turn inside the nest, as the focally observed female always entered the nest head first and reappeared backwards. This was also the case in the earliest observed appearance in the morning and on the last return to the nest in the evening. Therefore females of Q. major probably spend the night in the burrow head downwards. This is in contrast to the behaviour of females of Q. canariensis that spend the night inside the nest with their head orientated upwards towards the nest entrance, so that they appear head first in the morning (Mauss and Müller 2016). This is the result of a characteristic behaviour of the females of Q. canariensis that reappear backwards in the nest entrance after the last return to the nest in the afternoon, back out a few steps from the nest entrance, move forward on top of the turret and re-enter the nest metasoma first with the dorsal side orientated downwards (Mauss and Müller 2016). This distinct behaviour seems to be absent in Q. major.
The nest of Quartinia major consisted of a subterranean burrow terminated by a cell, which is principally similar to the nest architecture of Q. vagepunctata (Gess and Gess 1992) and Q. canariensis (Mauss and Müller 2016). The depths of the brood cells of Q. major below the ground surface were also within the range of these species measuring 20–24 mm in Q. major, 25–30 mm in Q. vagepunctata (Gess and Gess 1992) and 15–23 mm in Q. canariensis (Mauss and Müller 2016). Like the nest of Q. canariensis (Mauss and Müller 2016) the nest CH of Q. major is believed to have been multicellular and this was also suggested for nests of Q. vagepunctata (Gess and Gess 1992). Moreover, in all Quartinia species nesting in snail shells the nest is multicellular with up to 20 or even more cells (Gess and Gess 2010). The distant and isolated position of cell No. 2 in nest CH of Q. major is remarkable and resembles the situation in the nest of Q. canariensis (Mauss and Müller 2016). The isolated position of the sealed cell No. 2 demonstrates that it was excavated and provisioned by the female previous to the cell No. 1. As in the nest of Q. canariensis a connection from this isolated cell to the main shaft was no longer perceptible during nest excavation, indicating that it had been build at the end of a separate long secondary shaft that was either filled with soil by the female or that just collapsed after the brood cell had been sealed.
During nest excavation the female of Quartinia major backed out of the shaft carrying soil particles with her mouthparts, which is similar to the behaviour of Q. canariensis (Mauss and Müller 2016) and all other primarily ground nesting masarine wasps (cf. Gess 1996, Gess and Gess 2010, Mauss 2007). Therefore, these elements of the behaviour are probably plesiomorphic. As in other species of Quartinia (Gess and Gess 1992, Gess and Gess 2010, Mauss and Müller 2016) no observable liquid was used by Q. major during nest excavation.