Bees by behaviour

Summer finally arrived a dew days ago, and the bees have been enjoying the sunshine and warmth. I have been busy beewatching. It struck me that although there are hundreds of birdwatching books available, 'Beewatching' is not a shelf you will find in your trip to the library: number of beewatching books: nil, zilch, zero (sorry, no, I do not mean beekeeping). But why? Although bee watching has challenges, it is immensely rewarding. Plus points: (1) you can do it from the comfort of your garden, in fact gardens are amongst the best habitats to observe bees, as many flowers are available and you can pop out when weather conditions are optimal, therefore, no transportation needed (2) no binoculars or telescopes are necessary, and, (3) with a little investment on garden plants or a home-made bee hotel, you can be rewarded by new species coming to you and behaving as they do in the wild and even breeding in your garden: even small urban gardens can attract a large number of species. Given the lack of field guides on the topic, beewatchers are forced to made themselves out of experience, plenty of patience and readiness to learn. Although many bee species can only be identified under the microscope, some common garden species are relatively easy to identify while they are going about their business. I hope to show here that you can narrow down the group of bee or even identify to species level solitary bee species just by watching the various activities they are engaged with. 

Watch the flower

Many bees prefer to visit particular flowers. Some bee species are oligolectic, which means that they gather their pollen from one or a few flower species, others called polylectic, collect pollen from a wide variety of flowers. But even if the bees are polylectic, they often show some degree of preferences, therefore noting which the flowers they are visiting makes it easier to identify bees. This works even for males when they are patrolling and not feeding, as the males will check out the flower species that the females visit for nectar or pollen. A male Anthophora furcata, today, checked first one patch of Stachys sylvatica, then Lamium maculatum, then the other Stachys sylvatica patch. Surely, a female appeared later (below) to collect pollen in S. sylvatica, and the orange pollen she was carrying was probably from Lamium.

 Wool Carder Bee females are likely to be spotted shaving Lamb's ears (Stachys byzantina) hairs or feeding on the flowers. Megachile willughbiella loves cranesbills, campanulas and everlasting peas. Anthophora plumipes is strongly attracted to Lungwort and Comfrey. It also works the other way round: some plants are visited only by a reduced number of species: only a handful of garden species will visit foxgloves or honeysuckle.

Pay attention to detail
A large male bee patrolling campanulas is probably a leafcutter bee, Megachile willughbiella. To make sure, follow him as he flies, as he will settle regularly in a sunny, exposed place after bouts of patrolling (below).

Watch him carefully when he stops, he will almost invariably groom his head with his front legs a couple of times after landing - why? maybe wiping his eyes clean? -, and his white 'boxing gloves' will be visible even from a couple of meters away. If you can get closer, crouch down and look at him straight in the eye: he is all concentration, watching for females, rapidly twitching his head looking left, right or up. He does this for a few seconds and then flies off to carry on patrolling.

Leaf designing
A little bee flying from leaf to leaf, settles and walks sideways along the edge of the leaf briefly, like she is checking it, flies to the next leaf and then starts cutting an oval shape piece with her jaws.

Just finishing cutting the piece. Note that the same leaf has two other cut pieces.

In this shot you can see how she is holding the rolled piece of leaf with her legs and jaws

The edge of most leaves of my Enchanter's Nightshade plants, are all cut out. The culprit is the aptly named leaf-cutter bee, Megachile centuncularis. Leaf cutter bee females collect hundreds of leaf fragments to line their nests. As she cuts a fragment, she rolls it under her body using her legs and when she is finished she also holds it with her jaws before she flies up and then straight to her nest. If you can check the underside of her abdomen as she cuts the leaf, you will see the golden brush that characterises this particular species.

Spot the bully

I watched the first Wool Carder Bees of the year a couple of days ago in the local wildlife garden. Two males patrolling and feeding in a patch of Betony.

These are large, powerfully built bees, armed with five sharp prongs at the end of their abdomen. Males are territorial and they will readily attack and expel from their territory any other bees - even big bumblebees -, monopolizing the females that come to feed at their patch. When they rest, they keep their wings open at an angle, with their abdomen exposed. One of the males attacked a Bombus pascuorum feeding on the betony, and the bumblebee swiftly flew away.

Bottoms up!

Watch how the bee feeds on a flower. Leaf cutters (Megachile species) carry their abdomen tilted up, especially females, and rotate on the flower collecting pollen (see top shot). Look under their abdomen, you will see a broad brush of hairs. The color of the brush can help identify the species. They collect pollen on their rear legs and transfer it to the brush as they move over the flower. Megachille willughbiella females have a red and black brush, while M. centuncularis have an all golden one. Note that the hair color can be obscured by the pollen! This little video I took earlier today shows how she collects pollen on knapweed, a current favourite plant for bees in the garden.

Don't forget the little ones

Many bee species are small, you might have taken them for small flies in the past, but now that you are watching flowers up close you start to notice them. These two photos show flower preferences in two small Osmia species, which I only found in the garden this year. How could I have missed them before? 

Osmia caerulescens, the Blue Mason Bee, likes labiates like French Lavender, Sage or hedge Wouldwort

Osmia leaiana loves Knapweeds

Watch the seasons
Solitary Bees fly during relatively narrow periods, maybe two or three months in the species that have a single generation per year, so the time of year is often informative. Anthophora plumipes flies from March to early June, whereas Anthophora furcata has a short flying season in June and July.

There is so much to learn
As you become a beewatcher, you will develop a thirst for learning about the lives of these little critters that share your garden. For some of the species there is little information available, even common species have structures or behaviours that still remain enigmatic (what is the purpose of Megachile willugbiella boxing gloves or Anthophora plumipes hairy legs? why are the scopas of bees different colours, do they provide information to other bees, maybe when mating?). There are some resouces that I treasure, like my Bees of Surrey book by David Baldcock, or the BWARS site, and various bee identification forums, but as these are mainly concerned by identification and recording, I still want a beewatchers field guide.

Some day-flying moths

Following on the last post on moths, not all moths are nocturnal. Even if you don't want to go out there in the night looking for moths, you can come across many species of moth by day. There are over a hundred species of day-flying moth in the UK. Some species don't seem to care if it is day or night. Many day- flying moths are quite spectacular and often taken for butterflies. The following is is just a small selection of garden day flying moths.
 On the top shot, the Six spot Burnet, Zygaena filipendulae, on Betony, Stachys officinalis.

Silver Y, Autographa gamma, a strong migrant, it is often active during the day.

Mint Moth, Pyrausta aurata. The caterpillars of this small beauty feed on plants of the mint family.

The spectacular Hummingbird Hawkmoth, Macroglossum stellatarum feeding on Red Valerian

Small Magpie, Eurrhypara hortulata. Flies by day in June and July.

Cinnabar Moth, Tyria jacobaeae. In flight, it is often taken by a pink butterfly.

Moth bat detectors and the evolution of butterflies

This noctuid moth, a male Large Yellow Underwing, Noctua pronuba entered the house a couple of nights ago and my cat alerted me to it. This is a large moth, very variable in colour: females are lighter than males, and both sexes have a black mark near the end of the wing. As most moths, they have a highly developed sense of hearing and can hear ultrasounds by means of a timpanal ear behind their middle legs, in order to detect and avoid echolocating bats. When they detect an incoming bat, moths carry out unpredictable flight maneuvers: suddenly flying up, carrying our loops or power diving or dropping with closed wings. Large Yellow Underwings also suddenly drop to the ground when they are flushed during the day. Their coloration is cryptic and they blend well with the leaf litter, so once they fall to the ground they are hard to spot.
Avoidance of echolocating bats is thought to have been the selective pressure underlying the repeated evolution of bat detecting tympanal ears in moths. This happened repeatedly involving different anatomical regions in various moth families more than 50 million years ago. Surprisingly, the evolution of diurnal butterflies from their nocturnal moth ancestors appeared to have occurred at the same time: day flying and the subsequent radiation of butterflies resulted from a bat avoiding strategy.

More information
Yack JE, & Fullard JH (2000). Ultrasonic hearing in nocturnal butterflies. Nature, 403 (6767), 265-6 PMID: 10659835

Chewing me timbers!

From June to October, I find Ectemnius digger wasps in the garden. They are formidable hoverfly hunters and, close up, they look so fierce: all enormous, forward facing eyes and long, sharp jaws. Females bore nests in soft, dead wood using their jaws: a central burrow with lateral cells which they stock with flies. They will lay eggs on the flies and leave their nests for their larvae to feed on the flies when they hatch. They use dead branches on trees, laying wood and even visit bee hotels. Males are often found inspecting holes in dead wood, in search of emerging females.

Year after year, these wasps come back to my log pile under the barbecue. A few days back, I watched a female searching for suitable nest sites amongst the logs. She settled at the end of a lime log and started chewing the wood, producing abundant sawdust in the process (top photo). She carried on for a while, although at the end I think she settled for a different log, as today a large pile of sawdust had accumulated underneath (below).

For more posts on Ectemnius digger wasps click here.

A beautiful wasp-mimic hoverfly

While in the wildlife garden a couple of days ago, I noticed a large boldly marked hoverfly male hovering by the pond. I managed just a couple of shots, but this one is enough to identify it as Chrysotoxum festivum, a relatively scarce hoverfly in the north of England. Unlike other hoverflies, this genus has long, forward-pointing antennae, which contribute to liken it to a wasp. There is little information on the biology of this genus, although the larvae have been found inside ants nests, where they presumably feed on ant-attended ground aphids.