Tree bumblebee with foxglove

It is the 10th anniversary of the first recorded British Tree Bumblebee, a continental European species which crossed the channel on 2001, esblished successfully and has spread since to much of England. It's natural colonisation has been closely followed by Stuart Roberts, from the Bees, Wasps & Ants Recording Society (BWARS), who is collating a survey of this spread and has published an information sheet. The bumblebee is very easy to identify, with a tawny thorax and a black abdomen and a white tail. If you have any records you'd like to submit, check the website for more information. In my area, the tree bumblebee is doing really well and it is one of the commonest species at the moment. You can see them foraging on Ceanothus, cotoneaster, brambles and snowberry flowers. Today is the first time I have encountered them feeding on Foxgloves. This individual visited several spikes in succession, given me the chance to get a shot.

A blue glass snail

When lifting a pot to plant out today, I found this Glass Snail. There are four British species, and I think this is Oxychilus draparnaudi, given its relatively large size (a mighty 15 mm). Glass snails are named after their shiny, fragile and translucent shells when alive. After weathering the shells rapidly lose their lustre. Oxychilus shells are rather flat, which makes it easier for them to hide under pots or stones.

Given their small size - and their association with pots, nurseries and greenhouses - it is not surprising that several European Glass Snail species have been inadvertently introduced in temperate or subtropical regions around the world, including New Zealand, Australia and the U.S. and Canada. What perhaps is unexpected is that many Glass Snails, including O. draparnaudi are predators and their diet include other snails and slugs and their eggs, in addition to worms, and dead insects. They have even been reported to eat Garden Snails. When predating on snails, they attack the snail's body first with their radula and when they cannot access more flesh from the outside, they drill a hole on the shell to finish off their meal. The introduced populations, however, can be a threat for the native snail fauna and reductions or losses of local snail populations have been reported in areas with these predatory snails when compared with patches where they were absent in the U.S and New Zealand.

References
Barker, G.M. (2004). Natural enemies of terrestrial molluscs. CABI. DOI: 10.1079/9780851993195.0279. Here.
Karin Mahlfeld, Karin. Impact of introduced gastropods on molluscan communities, northern North Island. here.

A handsome snail

After a light shower yesterday, garden snails came out of their shells and went on a walkabout in search for food. Snails get some bad press in gardening circles, but most of my garden snails are feeding on the ground, on dandelion leaves or fallen vegetal material - OK, I am an untidy gardener now you know. I found this beautiful individual and thought I would take its portrait. It behaved quite well on a white plate and here you have it, on its best side.

Robbing and Buzzing

I took this shot of a male Bombus pratorum nectar robbing a few days ago: the bee's short tongue is inserted into a hole previously pierced at the base of the flower, where it can easily reach the nectaries. The other flower on the right has also these "drinking holes", which once present, are used by short or long tongued bees alike. The first B. pratorum workers of the year, which are very small, do appear to be able to feed through the corolla opening, and often visit intact comfrey flowers. A possibility is that the small workers are actually just collecting pollen - not nectar - using a  "buzzing" technique. This consists on holding onto the flower and then vibrating its wings - and making a characteristic high pitch sound. At certain vibratory frequencies, the pollen becomes dislodged from anthers and streams out of the flower, where is gathered by the bee.

B. pratorum worker collecting comfrey pollen, note the white pollen baskets

You might have seen bumblebees buzzing on poppies, as that way they dislogde much pollen, which covers their hairy bodies and that they then collect into their pollen baskets. These buzzing visits by bumblebees are common in several species, including comfrey, borage and kiwifruit and some of these flowers are actually pollinated this way. Not only B. pratorum, but other bumblebee species gather pollen in this way. Despite being relatively common, this behaviour is easily overlooked, for example, if you spot the bees casually, or from some distance, or there is background noise, but you can see the difference in sound between a bee collecting nectar (the first bee in the video, a B. pascuorum) and bee collecting pollen (a B. pratorum) in Comfrey in this YouTube video by pixiebaggins:

A resourceful bumblebee

Iris flowers are tricky for bees. They are quite unlike other flowers. Basically, each flower is made of a wide landing platform with striking nectar guides, but to be able to collect the nectar, bees have to push through a lip pressing against this platform - on top of this lip are first the stigma and then the anthers. As the bee enters, it often looks like it has to press with some force to lift the lip to form a gullet high enough. As she enters, its back presses against the stigma, depositing any pollen it might carry; then her back rubs against the flower's anthers, collecting some pollen. On her way back, the bee presses the stigma against a groove, so preventing self-fertilisation. This contraption ensures that visited flowers get cross-pollinated. Long-tongued bumblebees, Bombus hortorum and B. pascuorum and fork-tailed flower bees, Anthophora furcata, are able to enter the flower and feed the way the flower intended. Today I saw a buff-tailed bumblebee, Bombus terrestris, landing on the flowers of Iris versicolor, and appearing to have sensed there was nectar in them, tried in various ways to enter a flower, failing. The bumblebee started then biting the flower lip, in an unsuccessful attempt to gain entrance (top, check its jaws wide open). In other posts I have dealt with this piercing technique used to successfully steal nectar from tubular flowers like comfrey and honeysuckle, where this short-tongued bumblebee cannot reach the nectar.

Not this way - it missed the entrance and got on top of the lid

not this way either...

... and probing with its tongue for nectar after biting the flower lip.

Although this bumblebee was unsuccessful this time, the persistence of its behaviour after failing to get nectar first time round attests to the resourceful behaviour of this successful bumblebee.