August 30, 2026 Welcome to 'random bee', a short writing series where I choose a random page in the book "Bees of the World: A Guide to Every Family" by Laurence Packer, then read up on it and do a short write up. Today's random bee is: Genus: Megalopta Family: Halictidae Subfamily: Halictinae Tribe: Augochlorini check out the huge ocelli - the extra eyes on top of the head. by Ajay Narenda. Megalopta are super cool tropical bees that are active at night. Because this is so weird for a bee, they have been studied a lot. They are only found in Central and South america, so are associated with the tropics mostly and moist forests. There are 30 species in the genus, and they are in the Halictidae family (the sweat bees), which is an enormous family that is difficult to characterize. Most halictid bees are ground nesters, and the family itself has the biggest range of social behavior - ranging from eusocial to solitary and everything in between. Megaloptera actually nest in hollow twigs, so are called stem-nesters. The female creates a tunnel down the length of the twig or stem and seals off individual cells using chewed wood fiber. This group has a unique behavior - it is socially polymorphic, meaning that some individuals are solitary and some of them are social! Usually when bees are like this, the different geographic populations trend toward one social behavior vs the other. In this group, its thought to be influence by the dry season vs the wet season. The social individuals have a queen that produces a very small "hive" of 1-3 sterile worker bees. The queens influence their daughters to stay with the nest and help raise more workers (maybe this sounds familiar to some of you?). This isn't a true 'queen' but more like a dominant female. The workers have one of two jobs: foragers or nest-workers. Foragers collect pollen and nectar to feed the larvae with. Nest workers stay inside the nest to guard it or do hygiene work, cleaning out nest cells, etc. What traits do nocturnal bees have? All bees, and most insects, have 1-3 "extra" eyes on top of their heads (bees always have 3). These are called ocelli and they are very simple eyes for registering darkness and lightness, and thought to play roles in how organisms determine season by changing daylength (circadian rhythm type things). In Megaloptera, these occeli are HUGE and you can't miss them. Presumably they help the bee see at night. Megalopta's actual compound eyes are also more sensitive and have larger facets. The eyes seem to be specialized to the polarization of light that occurs at dawn or dusk, when the sun is rising or setting. The brains of these bees have also been studied extensively, and they use essentially their memory to remember where to land and how far to fly at night. Most nighttime bees are pale colored also - you think this would make them stand out more. Maybe it's so bees can find each other more easily? Some species are also just crepuscular - active at dawn and dusk, which are still pretty low-light conditions. Crepuscular bees have large ocelli also, but not as large as strictly nocturnal species. inside of the stem nest. from Kingwell et al., 2021. Why would bees be nocturnal? It's a good question. In the tropics, biodiversity is at its highest, with lots of other species competing for the same resources. There are many other insects and other bees in tropical regions. Being active at night reduces that competition, because fewer bees are active at the same time. Adult bees don't have a ton of active predators (most of the predation happens on the eggs or larvae), but for something like birds, which eat bees, these are going to be less active at night also. Naturally, the bees are known to visit plants whose flowers only open at sunset or at night. Two sexes, one body: Gynadromorphs are when an individual organism has a genetic anomaly where one side of the body is one sex, and the other side is the second sex. It's not too uncommon and is found in butterflies sometimes. It has been found twice in Megalopta. In the gynadromorphic bees, the female side has big toothed mandibles (for carving out a nest), and the male side has delicate mandibles. It results from a double fertilization event in the egg. sources: Kingwell, Callum, et al. "Cuticular and Dufour’s gland chemistry reflect reproductive and social state in the facultatively eusocial sweat bee Megalopta genalis (Hymenoptera: Halictidae)." Journal of chemical ecology 47.4 (2021): 420-432.