Hoplitis (Formicapis)

Müller, Andreas & Mauss, Volker, 2016, Palaearctic Hoplitis bees of the subgenera Formicapis and Tkalcua (Megachilidae, Osmiini): biology, taxonomy and key to species, Zootaxa 4127 (1), pp. 105-120 : 107

Biology of Hoplitis (Formicapis) and H. (Tkalcua)

Hoplitis (Formicapis) species show a close affinity to flowers of Rosaceae as pollen sources (for details see species accounts). Among the Rosaceae , herbaceous taxa such as Fragaria or Potentilla are the most important or even the exclusive hosts. While H. maritima ( Romankova 1985) and possibly also H. excisa might be strictly specialized on Rosaceae , H. robusta is polylectic with a distinct preference for Potentilla ( Fig. 2 , Tab. 1 ). Both H. maritima and H. robusta nest in insect burrows in dead wood and use chewed leaves to build cell partitions and nest plug (for details see species accounts). In the latter species, small pieces of wood are sometimes incorporated into the leaf matrix of the cell partitions.

Information on the biology of Hoplitis (Tkalcua) is available only for H. zandeni (for details see species account). Recent observations on Fuerteventura (Canary Islands) revealed that this species is polylectic harvesting pollen on flowers of at least six plant families ( Tab. 1 ), but probably not on Asteraceae . Interestingly, species of H. (Platosmia), the probable sister group of H. (Tkalcua), have a strong affinity to pollen of Fabaceae and/or Resedaceae ( Müller 2015) , which are also the two most important pollen host taxa exploited by H. zandeni ( Tab. 1 ). Whether this merely reflects the flower supply at the study sites or indicates some underlying phylogenetic pattern remains unclear. H. zandeni nests in empty snail shells and constructs 1–2 brood cells per shell ( Figs. 11– 16 ). Cell partitions and nest plug consist of chewed leaves densely mixed with sand grains ( Figs. 13–16 ). Interestingly, the nest plug is not built at the shell opening as in all other snail-shell nesting osmiine bee species known so far (A. Müller unpublished) but inside the shell about 1/3 to 1 whorl behind the shell aperture ( Fig. 13 ). In contrast to other osmiine bee genera such as Osmia , Protosmia or Wainia , where nesting in empty snail shells is rather widespread ( Kuhlmann et al. 2011; Müller 2016), snail-shell nesting in the genus Hoplitis has been reported so far beside H. zandeni only for the Afrotropic Hoplitis (Anthocopa) conchophila Kuhlmann and the Palaearctic Hoplitis (Hoplitis) fertoni (Pérez) ( Gess & Gess 1999, 2008; Kuhlmann et al. 2011; Sedivy et al. 2013b), indicating three independent origins of snail-shell nesting in Hoplitis .

Figures

FIGURE 1 – 8. 1: Hoplitis robusta, typical habitat in open subalpine forest with large proportion of dead wood (Swiss Alps, Sedrun, Grisons). 2: Hoplitis robusta, pollen collecting female on Potentilla erecta. 3: Hoplitis coreensis, clypeus and mandibles of female. 4: Hoplitis maritima, clypeus and mandibles of female. 5: Hoplitis maritima, tergum 7 of male. 6: Hoplitis excisa, clypeus and mandibles of female. 7: Hoplitis robusta, clypeus and mandibles of female. 8: Hoplitis robusta: tergum 7 of male.

FIGURE 9 – 14. Hoplitis zandeni. 9, 10: Semidesertic habitat on sandy ground with scattered shrubs of Salsola divaricata (Amaranthaceae), Launaea arborescens (Asteraceae) and Zygophyllum fontanesii (Zygophyllaceae) (Canary Islands, Fuerteventura, Costa Calma). 11: Nest in snail shell of Theba geminata, where the female had to burrow through sand masses that blocked the shell entrance. 12: Pollen loaden female at nest entrance. 13: Opened nest with one brood cell and nest plug built inside the shell. 14: Opened nest with inner side of nest plug consisting of sand grains irregularly glued together with leaf pulp.

FIGURE 15 – 18. Hoplitis zandeni. 15: Opened nest with threshold made of a mixture of leaf pulp and sand grains. 16. Opened nest with outer side of nest plug carefully worked with sand grains and leaf pulp to form a plane wall. 17: Yellowed leaf of Helianthemum canariense with chewing marks along apical and left margin. 18: Male resting on the ground.

Tables

TABLE 1. Pollen host spectrum of Hoplitis (Formicapis) robusta and Hoplitis (Tkalcua) zandeni based on 22 female pollen loads from 20 different localities in Switzerland (n = 13), Austria (n = 2), Finland (n = 5) and the USA (n = 2), and on 29 female pollen loads from 6 different localities on Fuerteventura (Canary Islands). For H. zandeni, results of the analysis of 14 brood cell provisions originating from 12 nests from the same locality on Fuerteventura are additionally given.

Plant family	Plant genus, subfamily or species	% pollen grain volume in pollen loads	number (%) of pollen loads with this pollen type(s)	number (%) of pure pollen loads	number (%) of brood cells with this pollen type(s)
Hoplitis robusta
Rosaceae	Potentilla	68.1	18 (81.8)	13 (59.1)	-
Cistaceae	Helianthemum	19.8	6 (27.2)	2 (9.1)	-
Fabaceae	Medicago	6.3	1 (4.5)	0 (0)	-
Rosaceae	Rubus	2.7	1 (4.5)	0 (0)	-
Asteraceae	Cichorioideae	1.1	1 (4.5)	0 (0)	-
Ranunculaceae	Ranunculus	0.3	1 (4.5)	0 (0)	-
unknown		1.7	2 (9.1)	0 (0)	-
Hoplitis zandeni
Fabaceae	4 different types	34.9	16 (55.2)	2 (6.9)	13 (92.6)
Resedaceae	Reseda lancerotae	29.8	15 (51.7)	4 (13.8)	14 (100)
Frankeniaceae	Frankenia laevis	15.6	12 (41.4)	0 (0)	9 (64.3)
Boraginaceae	Heliotropium erosum	11.4	10 (34.5)	1 (3.4)	11 (78.6)
Cistaceae	Helianthemum canariense	8.1	6 (20.7)	0 (0)	12 (85.7)
Plantaginaceae	Kickxia sagittata	0.3	3 (10.3)	0 (0)	4 (28.6)