# Megachile parietina (Geoffroy, 1785), a new addition to the bee fauna of the Maltese Islands (Hymenoptera: Apoidea: Megachilidae)

Thomas Cassar

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Thomas Cassar. Megachile parietina (Geoffroy, 1785), a new addition to the bee fauna of the Maltese Islands (Hymenoptera: Apoidea: Megachilidae). OSMIA, 2024, 12, pp.1-4. 10.47446/OSMIA12.1. hal-04448028

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ARTICLE

# Megachile parietina (GEOFFROY, 1785), a new addition to the bee fauna of the Maltese Islands (Hymenoptera: Apoidea: Megachilidae)

Thomas CASSAR<fnref n="1" />

CASSAR, T. (2024). *Megachile parietina* (GEOFFROY, 1785), a new addition to the bee fauna of the Maltese Islands (Hymenoptera: Apoidea: Megachilidae). *Osmia*, **12**: 1–4. https://doi.org/10.47446/OSMIA12.1

**Abstract**

*Megachile parietina* (GEOFFROY, 1785), the black mud bee, is recorded from the Maltese Islands for the first time on the basis of two adult nesting females and four nests from Pembroke (north-east of Malta). This addition to the Maltese entomofauna brings the number of bees known from the archipelago to 106. The possibility that this species could be a suitable pollinator of the endemic orchid *Ophrys melitensis* (SALK.) DEVILLERS-TERSCHUREN & DEVILLERS, 1994 is discussed, and further investigation is encouraged.

**Keywords** | *Chalicodoma* • pollinators • new record • orchid • Mediterranean basin

**Megachile parietina** (GEOFFROY, 1785), un nouvel ajout à la faune des abeilles des îles maltaises (Hymenoptera : Apoidea : Megachilidae)

**Résumé**

*Megachile parietina* (GEOFFROY, 1785) est signalée pour la première fois dans les îles maltaises sur la base de deux femelles adultes nicheuses et de quatre nids à Pembroke (nord-est de Malte). Cet ajout à l'entomofaune malaise porte à 106 le nombre d'abeilles connues de l'archipel. La possibilité que cette espèce puisse être un pollinisateur de l'orchidée endémique *Ophrys melitensis* (SALK.) DEVILLERS-TERSCHUREN & DEVILLERS, 1994 est discutée et une enquête plus approfondie est encouragée.

**Mots-clefs** | *Chalicodoma* • polliniseurs • nouveau signalement • orchidée • Bassin méditerranéen

Recu • Received | 18 July 2023 || Accepté • Accepted | 06 February 2024 || Publié (en ligne) • Published (online) | 10 February 2024

Reviewers | Y. BRUGEROLLES • M. ZAKARDJIAN || https://zoobank.org/BD73C2C6-C9E7-40EE-89AD-CB4CB09D7090

INTRODUCTION

The bees of the Maltese Islands have not been extensively studied, but the last decade has seen a renewed interest in the Maltese apoidean fauna; so far, 105 species from five families have been recorded in the archipelago, in addition to three dubious records (ALFKEN, 1929; VALLETTA, 1971, 1979; SCHEMBRI, 1982; BALZAN *et al.*, 2016, 2017, 2023; CASSAR & MIFSUD, 2020a). The known bee fauna of the Maltese archipelago is composed largely of species with widespread distributions throughout the Palearctic, with nearly all species also found elsewhere in South Europe, and the bee faunae of Sicily and Malta share a strong resemblance

(BALZAN *et al.*, 2016). The bee fauna of the Maltese archipelago is still not wholly known, and ongoing studies continue to reveal new discoveries. This article reports one such discovery of another widely-distributed Palearctic species – the first record of the black mud bee *Megachile parietina* (GEOFFROY, 1785). The discovery of this species in the Maltese Islands is not only of interest from an entomological perspective as it is possible that *M. parietina* may act as a pollinator for the scarce endemic orchid *Ophrys melitensis*.

MATERIAL AND METHODS

While filming orchids in Pembroke, north-east Malta, the author encountered a dark bee, around 15 millimeters in

length, constructing a pedotrophic nest cell attached to exposed coralline limestone. After further investigation, an

*Osmia* est une revue en libre accès publiée par l'Observatoire des Abeilles (France) sous licence Creative Commons Attribution International CC BY 4.0 qui autorise la reproduction et la diffusion du document, à condition que la source soit explicitement citée.

*Osmia* is an open-access journal published by the Observatory of Bees (France) under Creative Commons Attribution International License CC BY 4.0 which allows the reproduction and distribution of the document, provided the source is explicitly cited.

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OPEN ACCESS

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<footnote n="1">¹ [TC] 11 Elmers Court, Post Office Lane, Beaconsfield, UK – HP9 1QF, Buckinghamshire, United Kingdom • thomas.m.cassar@gmail.com
https://orcid.org/0000-0001-8703-813X • zoobank https://zoobank.org/0293AFB2-C8AA-44D8-B918-F8CE6EC783F1</footnote>
additional female and three completed nests were found, and the bee was identified to belong to the taxon *Megachile parietina* (GEOFFROY, 1785) based on morphological traits described in PRAZ (2017). The areas of Pembroke in which the bees were collected and observed are part of an expanse of coastal karstic garigue, characterized by exposed, weathered coralline limestone with shallow depressions (kamenitzas), terra-rossa soils, low-growing aromatic shrubs,

and geophytes. The area is subject to anthropic activities; a large reverse-osmosis plant occurs nearby; a metal walkway cuts across the garigue; and some parts nearer to the shore are subjected to the activities of the Armed Forces of Malta. In more disturbed areas of the garigue, such as the margins close to walkways, footpaths and roads, the vegetation becomes increasingly characterized by therophytes and ruderal species.

## NEW RECORD

### Megachile (Chalicodoma) parietina
(GEOFFROY, 1785)

#### Material examined

Malta. 1 ♂ (TC), Pembroke, 3.IV.2023, T. CASSAR leg.; 1 ♀, Pembroke, 8.IV.2023, T. CASSAR obs.

#### Notes

This species is a widely distributed one, occurring in West, East (including North Caucasus and Crimea) and South Europe, much of the Middle East, Central Asia and North Africa (FATERYGA et al., 2018). *Megachile parietina* collects particles of soil and binds them with a labial secretion, constructing dome-shaped nests containing multiple cylindrical cells provisioned with pollen and nectar – favouring that of Fabaceae – all sealed with mud. The nests are usually built directly on exposed rock surfaces and walls but may occasionally be constructed around twigs and branches (REBMANN, 1969; WESTRICH, 1989; MÜLLER et al., 1997; VEREECKEN et al., 2010; GOGALA, 2014). In many respects, the nesting biology of *M. parietina* closely matches that of its consubgener *Megachile sicula* (ROSSI, 1792) which is common and widespread in the Maltese Islands and occurs in the karstic coastal garigue of Pembroke (figure 1), where the specimens of *M. parietina* were found.

<figure><img src="image_5.png" /><figcaption>**Figure 1.** General habitat in which bees were encountered constructing nests – coastal karstic garigue with rocky exposed ground, shallow soil and low-lying aromatic shrubs. Photo T. CASSAR.</figcaption></figure>

Two females were encountered in Pembroke. The first, which was collected by the author (figure 2), had recently begun constructing a pedotrophic nest in a shallow depression in exposed limestone, with one cell complete and the wall of another still being constructed. The second was encountered 300 m away (coordinates: 35°55'59.1" N, 14°28'52.0" E) in the very final stages of completing an entire nest (also on exposed coralline limestone) by sealing the cells, and another two freshly completed nests were found less than one m from this activity (figure 3). This latter female was filmed by the author but not collected.

<figure><img src="image_6.png" /><figcaption>**Figure 2.** *Megachile (Chalicodoma) parietina* (Geoffroy, 1785), ♀, from Pembroke, Malta Front view and lateral view. Photo T. CASSAR.</figcaption></figure>

Because of this species' widespread distribution in the Mediterranean, *M. parietina* can be assumed to be a native species which has simply remained undetected during previous samplings of Maltese Apoidea. However, the species is a large and distinctive one, having a robust build, conspicuous black colouration, wholly infuscated wings and an upper bound of length closely approaching two centimetres. Thus, it would seem unlikely to avoid detection
<figure><img src="image_7.png" /><figcaption>**Figure 3.** Completed nest of *M. parietina* from Pembroke, Malta. Photo T. CASSAR.</figcaption></figure>

unless particularly rare, and the possibility that it may
represent an introduced species for Malta is not entirely
excluded. Certainly, other hymenopterans are known to
have entered the Maltese Islands (and subsequently
established themselves) through the accidental transport of
pedotrophic nests attached to goods, marine vessels and so
on (CASSAR & MIFSUD, 2020b). However, it seems unlikely

that *M. parietina* would construct its nest on a marine vessel itself, as it tends to build its nests directly on exposed rock and, less frequently, branches and twigs (REBMANN, 1969; VEREECKEN *et al.*, 2010). The most likely explanation in the view of the author, therefore, is that the bee represents a native species which has remained undetected due to (i) its rarity, (ii) the lack of previous sampling for bees carried out in a particular area to which it may be localized (Pembroke), and/or (iii) the lack of previous sampling for bees carried out during the flight period of this species.

It is interesting to note that in both areas in which the author
observed females of *M. parietina* constructing nests, small
populations of the endemic and scarce orchid *Ophrys
melitensis* (SALK.) DEVILLERS-TERSCH. & DEVILLERS (figure 4)
were in flower. So far, the only known pollinator of this plant
is the male of *Megachile (Chalicodoma) sicula*, with pollinia
being attached to the male's frons upon pseudocopulation
(SALKOWSKI, 2000). The possibility that males of *M. parietina*
could also serve well as pollinators of this orchid is not
entirely excluded; *M. sicula* and *M. parietina* are closely
related species (PRAZ, 2017). The author remained at the site
were the second *M. parietina* female was completing its nest
and closely observed the *Ophrys melitensis* flowering there
for four hours (10:00 – 14:00) a day for three days (8–10 April
2023), but no males of *M. parietina* were seen
pseudocopulating with *O. melitensis*. Nevertheless, the
author encourages further investigation to ascertain
whether this bee may be an additional pollinator of the
scarce and endemic taxon *O. melitensis*.

<figure><img src="image_8.png" /><figcaption>**Figure 4.** One of multiple *Ophrys melitensis* plants growing about one metre from nesting *M. parietina*.
Photo T. CASSAR.</figcaption></figure>
REFERENCES

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