The Dialogue Pages

Black resin bees

I started my love of resin bees in 2005 and was hoping to be able to study this bee for my honours project. Unfortunately, it wasn't possible to acquire a large enough population for my studies at the time. But not to be perturbed, I continued my efforts to increase the natural populations in my area and just learn what I could at home.

Resin bees are in the genus Megachile (previously Chalicodoma) and species in this genus have been reported in all states of Australia, except Tasmania (link search for genus distribution). This doesn't mean they aren't in Tasmania, it just means they haven't been reported. Resin bees are called such because they use plant resins to make their nests, within rock crevices or in holes made by wood boring beetles (Cerambycidae and Buprestidae) or moths (Cossidae and Hepialidae). Because wood borers are a major problem for building maintenance, we tend to remove any wood that contains borer holes. Therefore, we are removing the natural habitat of these and many other insects.

It is possible to provide attractive, artificial nests for resin bees. To do this, simply drill holes in blocks of hardwood (link to how to make resin bee nests), and placed them in a sheltered place. When I first did this, nothing happened for one year, but during the second year I started to see bee activity. Each year since then, I have placed more drilled blocks around my garden and their holes have been occupied by an assortment of insects. This includes mud wasps, ants, wasp–mimic bees (Hyleoide species) and three different species of resin bee (Figure 1).

Figure 1 Drilled hardwood blocks demonstrating an array of different residents, including wasps, ants and resin bees. The greater variety of hole size will bring in a greater diversity of insect.

So, how did I figure out I had three species of resin bee? Online searches and, of course, I enlisted the help of Michael Batley yet again. The first specimen I collected was a couple of years ago, when I still pinned specimens. It was a 15 mm long, male (drone) Megachile lucidiventris (Figure 2). The drones are often more useful than the females when trying to identify any bee species. Here, the M. lucidiventris male displays the very distinctive feature of expanded forelegs. These structures are like large padded mittens (Figure 3 & Figure 4) and are used in the mating ritual. When the male and female couple, notches in their legs and bodies lock together. The male then covers her eyes with the expanded forelegs and he guides them in their nuptial flight. It all sounds very romantic.

Figure 2 Megachile lucidiventris drone showing distinctive orange facial ‘fringe’ and expanded forelegs.
Figure 3 Inner aspect of the expanded foreleg of a Megachile lucidiventris drone.
Figure 4 Outer aspect of expanded foreleg of a Megachile lucidiventris drone.

I haven't been able to collect a female of this species as yet, but apparently she has quite a lot of which hair right across the first segment of the upper side (dorsal) of the abdomen (T1) (Figure 5). When compared to Megachile punctata females, which have a thin scattering of hair medially, but dense patches laterally on T1 (Figure 6). M. punctata has tiny pock marks over the exoskeletal surface (Figure 6) thus, the name (punctatus Рspeckled, in the Latin). The M. punctata are also about 15 mm long.

Figure 5 Image from PaDIL of Megachile lucidiventris female, showing dense hairs on the upper surface (dorsal) of the first abdominal segment (T1).
Figure 6 Female Megachile punctata showing hair patterns on the dorsal surface of the first abdominal segment (T1). The specked indentations can be seen on the head and thorax.

The females have scopal hairs on the underside (ventral) of abdomen, for carrying pollen (Figure 7), whereas the males do not (Figure 8).

Figure 7 Female Megachile punctata showing the scopal hairs on the under surface (ventral) of the abdomen.
Figure 8 Megachile punctata drone without a scopa. The drone has an orange ‘fringe’. Note his long tongue, for feeding on flowers with deep, connected petals (corolla).

The male M. punctata has an orange ‘fringe’ (Figure 8) (similar to the M. lucidiventris drone) whereas the female's face is a similar colour to her body (Figure 9). Resin bees have very strong jaws (mandibles) for manipulating plant resins and leaf material to make their nests (Figure 9).

Figure 9 Megachile punctata female with facial colouring which is similar to her body. Note the large jaws (mandibles).

The most recent resin bee I have encountered is Megachile aurifrons (aurum – gold; frons – forehead, in the Latin). The female of this species has a vivid orange / gold facial fringe (Figure 10 & Figure 11). In most species of Megachile, it is the male which has the fancy hair do. She also sports a protrusion, known as a ‘pig–snout’, in the middle of her face which is a distinct taxonomic feature. M. aurifrons is the only Megachile that has those magnificent red eyes. When comparing images in PaDIL, those distinct red eyes could not be found. This is because when the bee dies, the eyes fade after only a few days. M. aurifrons has thick white hair over much of its body and the males have expanded forelegs (hopefully there will be an image next summer).

Figure 10 Female Megachile aurifrons has vivid orange / gold facial hair, protrusion in the middle of her face and magnificent red eyes. She also has a great deal of thick white hair on her body.
Figure 11 Megachile aurifrons at the entrance of her nest.

Although I have seen resin bees foraging in my garden I have, as yet, been unable to get an image of one so I have included a beautiful image here by Erica Siegel (Figure 12). Apparently resin bees are very partial to flowers in the pea family (Fabaceae). Guess I'd better start planting…

Figure 12 Female resin bee foraging on a pea flower. Note the pollen collected in the scopa.

For next season, I plan to build some nests with observation panels. I hope to be able to observe how the three species' nesting behaviour differs. Stay tuned…