In late April, I observed a heap of newly dug soil near the edge of a pot at my balcony area. There was a round open entrance at the top of the heap which was sheltered under a seedling of a mangrove fern, either Acrostichum aureum or Acrostichum speciosum. At first, I suspected that it might be the work of a beetle that burrowed into the soil to lay it eggs. The mystery was solved on 16 May when I saw a black-coloured insect went into the hole but did not manage to catch a good glimpse of it. I patiently waited with my camera hoping that it would emerge. My effort was rewarded when I saw the creature’s head slowly sticking out from the hole. As it flew off as soon as it emerged from the hole, I only managed to snap a few pictures of its head region. It was a ground-nesting bee.

In that pot was a trimmed treelet of Wild Cherry Tree (Muntingia calabura) that was already flowering. The seeding of the mangrove fern appeared on its own though I had earlier mistaken it as a Tongue Fern (Ophioglossum reticulatum) which had shown up in my other pots in 2 occasions, July 2016 and June 2015. No wonder that I had not seen any fertile spike from it for a long time. I had wanted to transfer the seedling to another pot but with the bee building a nest underneath it, the plan will have to be put on hold for a while.

There was a heavy rain after I took the pictures of the bee. The nest appeared to be intact; sheltered by the mangrove fern seedling. A few days later, I caught sight of the bee entering the nest but it was too fast for me to make any good observation on its body features. As the days went by, I continued to watch over the nest from time to time. At the time that I wrote this short note, I had seen at least 3 bees entering the nest. Finally, I got one blurry shot of the abdomen of the bee when it flew off.

I found a short report that described the sighting of Pearly-banded Bee (Nomia incerta) entering into its nest in Singapore [1]. Nomia bees are commonly known as Alkali Bee or Sweat Bee. The SARE website has a comprehensive write up on the underground nest of this bee as well as its contribution to agriculture. I noted from another report that Black Leafcutter Bee (Megachile atrata) found in Singapore also build its nest underground [2].

Hopefully, I will be able to take some good pictures of the full-body of the bee before they abandon the nest to allow the identification of the bees.

References:

[1] Soh ZWW. Pearly-banded bees Nomia incerta nesting in flower pots at Pasir Ris. Singapore Diversity Records 2016:113-114. | Read article |

[2] Ascher JS, Risch S, Soh ZWW, Lee JXQ, Soh EJY. Megachile leaf-cutter and resin bees of Singapore (Hymenoptera: Apoidea: Megachilidae). Raffles Bull Zoology 2016;Suppl 32;33-55. | Read article |