A beesy beesy day

We've had a lovely, mild, quite sunny day today. Bees came out of their various hiding places and gorged on the garden flowers. Top bee magnets were the hardy geraniums and the hedge woundwort. At least one old Osmia rufa was still about, very late for this spring species. The first Anthophora furcata of the year turned up, at the usual time of the year. She fed on Hedge Woundwort (above, note how thick the bright red tail looks) and Iris. A male was also about.

Bombus pascuorum entering Iris.

 The only B. lapidarius I saw today

Osmia caerulescens female sunbathing

Competition for the hardy geranium, Bombus hypnorum and Osmia rufa

Osmia rufa leaving hardy geranium, note the visible 'horns'

Megachile centuncularis on Bird's foot trefoil

 Bee list

1. B. hypnorum hardy geraniums, cotoneaster. Males and Queens about.
2. B. pascuorum foxglove, purple toadflax, hedge woundwort.
3. B. hortorum foxglove, hedge woundwort, lamium maculatum
4. B. terrestris, Stachys byzantina, trying to feed on Lamium maculatum
5. B. lapidarius poppy, just one.
6. B. pratorum hardy geraniums, cotoneaster
7. Megachile willughbiella male on thyme, stachys
8. M. centuncularis birds foot trefoil, hardy geraniums
9. Anthophora furcata male patrolling, 1st female of yr., Teucrium, Iris, Hedge woundwort, Herb robert.
10. Osmia rufa, hardy geranium
11. O. caerulescens, sunbathing
12. Honeybee Philadelphus

A scarily beautiful ichneumon

This is the largest and most spectacular ichneumon I see in my garden, Pimpla sp. They are parasitoids of moth caterpillars. The females walk jerkily over the vegetation, constantly tapping the surface of leaves with their twitchy antennae searching for caterpillars. Once they find a suitable host, they use their dagger-like ovipositor to hypodermically inject the caterpillar with an egg, which will develop into the wasp larvae. The larvae feeds on the caterpillar's organs and kills it before emerging like an adult wasp. There are over a thousand ichneumon species in the UK, and they are often difficult to determine without microscopic examination. They are also quite tricky to photograph due to their nervous disposition, so I cooled this one in the fridge for 20 minutes before photographing, and it only took a couple of minutes to fly away!

Showing its plumes

This Morning Glory Plume Moth was resting on a fence in a unusual posture, showing its feathery hindwings, the reason for its name. Normally, the moth will rest with wings folded and stretched in perpendicular angle to its body, making a T shape. Maybe the breeze disturbed it. I like the shadow of its forewings on the grainy, stained wood. I have found no photos of live E. monodactyla in this position.

Fat lily beetle larvae

While checking the underside of my lily leaves for lily larvae I found this giant on the 22 of June. A fully developed larvae, no longer protected by its own poo, but ready to drop to the pot soil to pupate. Still haven't found any pupa, might try later in the year when I repot some congested lilies.

A Pellucid Hoverfly

This is the striking, and relatively common hoverfly, Volucella pellucens. Yesterday afternoon I watched this female feeding on dogwood blossom. It is a very large fly, mostly black, with a translucent, pale first abdominal segment. Males are very obvious this time of year, as they hover, a few meters high, near trees. Even in flight, their colour pattern and size makes them easy to identify. They live in woodland and park glades, although I have also seen it a few times in my garden.
The adults feed on umbellifers, buddleia and bramble flowers, amongst others. An interesting aspect of this hoverfly life cycle, although still relatively poorly known, is that its larvae are found inside the nests of social bees and wasps. Adult hoverflies are apparently able to enter unnoticed the well guarded nests, and lay their eggs in the nest. The larvae feed at the bottom of the nest, scavenging on dead adult bees or wasps or grubs, pollen and dropped food and other debris. In the autumn, when the nest is vacated, the larvae might move into the combs, when they finish off any late grubs.

More information
Stubbs, A. E., & Falk, S. J. (1983). British hoverflies. An illustrated identification guide. British Entomological and Natural History Society.

Elder aphid networks

The photo above shows a dense colony of Elder aphids, Aphis sambuci, many individuals of different ages feeding close together. They are likely to be all a clone, female descendants of a single founding female that emerged from an egg early in spring, and identical genetic copies of her. Elder aphids forms this characteristic ash grey patches on tender elder stems. The aphids suck the elder sap using their piercing mouthparts. Having a close look at elder aphids gives you an opportunity to learn to learn about ecological networks in a few minutes of observation. All the photos in this post were taken in the space of seven minutes this morning on my way to work on the same young elder bush.

 Despite the fact that elder, Sambucus nigra, has relatively few insect predators, most likely due to it having cyanogenic chemicals in its leaves, elder aphids are an important link in networks making use of elder sap. 

Ants have a mutualistic relationship with the aphids. They benefit from the aphids honeydew by soliciting them to excrete it, taping them with their antennae. The sugary rich liquid is consumed by the ants and their larvae. The ants treat the aphids as their domestic animals. The aphids benefit too, as potential predators or parasites are pursued or attacked by the ants.

But the ants can't totally defend the aphids from their numerous predators. Here a female hoverfly, Epistrophe eligans, lays eggs on a patch of elder aphids.

A hoverfly egg is visible on the centre of this photo, on the edge of the aphid colony.

See the patches cleared of aphids in this patch? They are due to predation by the green hoverfly larvae just visible amongst them. Surrounded by food, the larvae will gorge on the aphids and grow rapidly.

This hoverfly larvae (possibly Epistrophe eligans) is likely to be ready to pupate.

Not only hoverflies, ladybirds are attracted by this aphid bonanza and adults land on the elder, possibly attracted by the smell of aphids. A Harlequin sunnies itself on a leaf...

...while an active 2 spot searches about.

Ladybirds have laid their bright yellow egg clutches on or under the leaves, near the aphid colonies.

...here visible on the background. I couldn't find any ladybird larvae today on this elder. 

This fly enjoyed licking the honeydew on a leaf. Some species of butterflies, like the Speckled Wood, also takes advantage of honeydew.

Five species (2 ladybirds, a fly, an ant and a hoverfly) thriving on elder aphids. If I had waited a bit longer, or being a bit luckier, I could have witnessed tiny parasitoid wasps that lay their eggs inside the aphids and eat them from the inside!

Tree bumblebees mating

For the last few weeks, Tree bumblebee males have been travelling full speed around the garden marking leaves and stems with pheromones to attract queens. The males and new queens have been produced by bumblebee nests as they are reaching the end of their life cycle. Males leave their natal nest and then hang around the entrance of nests possibly hoping for a queen to emerge. Workers are most likely found dead than alive once the males and queens fly from the nest as their role is completed.
I watched a Tree bumblebee nest in my local wildlife garden, as common in this species, they chose high places, and nest boxes and under eaves are the most easily spotted nest sites. A cloud of males hovered around the entrance.

 Today I found the mating pair above on hogweed, the first I find for this species. It is hard to believe that the Tree Bumblebee was not found in N England 10 years ago, now it is so common and widespread. Here is the distribution map for this species from BWARS B. hypnorum project.
More info on B. hypnorum in BugBlog here.

Strawberry Snail and Girdled Snail

Continuing today with the snail theme due to the wet weather. My 5 yr old daughter has a keen eye for little bugs, and today, all on her own found these two snails on a front garden in my street. Two species that we haven't found in our garden.

This is the Strawberry Snail, Trichia striolata a relatively small snail (about 10 mm wide), with a dull, finely sculptured round shell and dark body. The shell colour is variable, but this is the most common in my area. The shell has got an 'umbilicum' underneath, an open space between the shell worls. It genus name refers to the fact that the snail is hairy when young.

This is a similarly sized snail, the Girdled Snail. This angle shows the white keel that makes them easy to recognise. I have written about them before.

The courtship of garden snails

While having a cup of coffee in the conservatory during breakfast, I noticed a pair of snails, one of them with its genital pore a bit everted. Aroused snails! It was 10:09. I quickly finished my coffee and came closer. Despite coming across tens (hundreds?) of slumbering mating snails for years, I had never witnessed the actual preliminaries of it, which was now taking place just behind the conservatory glass, on its wooden frame. The series of events was fascinating, by its slow, but surely developing tempo, its tactile nature, its synchrony, and the dance-like quality of it. First the snails approached each other, with their heads up, appearing to avoid exposing their gonopore (an opening behind the right hand side of their heads from which their penises emerge and where their vaginas open) to their partner, while at the same time touching each other's gonopores with their mouths in long, slimy kisses, and tentacles touching, occasionally retracting their heads. One of the snails appeared more keen, while the other regularly turned round and then back, each time coming closer to its partner.
Then courtship became more intense, both snails everting their penises and aligned their bodies toward each other, exposing their right sides to each other. Finally, after a couple of hours, they were sleeping in their copulating embrace, and their eyes retracted. I missed the darting and I couldn't see any protruding darts. Here is a slide show.

Every now and then, I checked on the snails. They slept on the frame of the conservatory most of the day (at 16:45 they were still mating). I just checked (21:40), and only one remains. The duration of mating in this species is about 7 hours.
I have uploaded a video with an early and a later sequecing of the courtship.

No matter how long you've been acquainted with a particular species, there is always something surprising and wonderful you might still witness.

Ants and cherry laurel nectaries

 On passing by a hedge of Cherry Laurel, Prunus laurocerasus, we notice ants. Lots of Black Garden Ants, Lasius niger, walking all over the leaves. We creep closer and see little round marks on the base of the leaves that the ants are paying special attention to. They are nectaries, nectar producing organs in plants, which are most commonly found at the base of flowers. In about 1% of plants (including several species of the genus Prunus, including cherries) these organs are also found on leaves and are called 'extrafloral nectaries'. Extrafloral nectaries are part of a mutualistic relationship between plants and ants, in which both parts benefit. The plants give away the sweet nectar which feeds the ant, and in turn the ant defends the plant. By visiting the plant to obtain nectar ants come across herbivorous insects, particularly caterpillars, that might feed on the leaves, and prey upon them.
 Other nectar-loving insects take advantage from this easy to reach nectar production, and often, bees and bumblebees are found feeding in nectaries. Bees and bumblebees behave in this case as 'nectar robbers' as they do not benefit the plant at all (unlike when they feed on the floral nectaries). In this case, the ant is the one benefiting the plant. If you like the bright green, glossy leaves of the cherry laurel to stay that way, you might want to leave these ants well alone.

Ant feeding on a nectary. There is another pale, round nectary just above the ant.

Male Bombus pratorum visiting the cherry laurel

Marmalade fly ovipositing

Aphids are everywhere now, under tree leaves, on herb stems and on tender bush shoots. But they have many enemies. Amongst them, many hoverfly species are busy egg laying, carefully choosing their oviposition sites to be next to rows of fat aphids. This is my first photo of the year of a Marmalade Fly, Episyrphus balteatus: a female laying on a Wood Avens stem full of aphids. It was the only shot I took before she flew away. Soon their voracious larvae will be munching aphids away.

Watching bees on foxgloves

June is peak Foxglove, Digitalis purpurea, season. This year, we have quite a few in the garden, and luckily one of them faces the conservatory, which allows me to observe visiting bees quite closely. Today I watched the bees feeding on it in sunny spells between showers. Foxgloves are said to be adapted to be pollinated by bumblebees: they have large, bell shaped flowers with a large landing lip and hairs that might deter smaller bees or other insects from entering. Indeed, bumblebees, and particularly long-tongue species, can reach the nectar deep inside the flower and actually pollinated it are the main visitors. A study in N Yorkshire found that Bombus hortorum (top, individual leaving flower with pollen load, and another individual just visible inside a lower flower) was the main visitor and preferred this flowers when available, but another study in Belgium found that B. pascuorum was the main visitor. The tree bee Bombus hypnorum is also a regular. All three species are commonly found on floxgloves flowers in my garden, with B. hortorum being the most common visitor. But other bumblebees, including those with short tongues do often collect pollen by 'buzzing' inside the flower even if they cannot reach the nectar.
 A few solitary bees also visit foxgloves. In my garden the forked tailed flower bee Anthophora furcata regularly visits them, and more rarely the carder bee Anthidium manicatum.
As relatively few species feed on this species, it is a good starting plant to familiarise yourself with bumblebees.
Today, I watched four bee species visiting this particular foxglove stem.

A male A. furcata (above) jumped on each visiting bumblebee to check them out, but was obviously feeding also on nectar. I haven't seen females around yet. The male has similar size and colour than a honeybee, but it has a bright yellow face and a visibly long tongue.

Bombus hortorum is the bumblebee with the longest tongue in the UK (above, with tongue extended). It can also be recognised by its double yellow band formed by the rear of the thorax and the front of the abdomen, and its white tail.

B. pascuorum is the most common all-brown bumblebee in gardens. 

Bombus hypnorum is a very distinctive bumblebee, three coloured: brown/black/white.

The stout black abdomen with lateral yellow patches of the Wood Carden Bee Anthidium manicatum which visited on 1/07/2011.

 Foxglove flowers open from the bottom of the stem towards the top. The plant reproductive parts are located on the roof of the flower, four stamens and a pistil in the middle, so that the body of a bumblebee entering the flower rubs against them. To reduce self-pollination, the flower anthers open first, delivering a pollen load onto bumblebees feeding. Five days later, when the pollen is likely to be exhausted the pistil becomes receptive, increasing the chances that it will be pollinated by the pollen of a different plant. I cut three flowers of a white foxglove in the garden and removed the roof of the flower to expose the reproductive organs. The one on the left, from the top of the flower spike just opened. The lobed yellowish sacs are the closed anthers, and the spike in the middle is the pistil, also closed and attached to the flower roof. The middle flower has open anthers and the pistil, although closed, has started to detach. On the left is the oldest flower from the bottom of the flower spike. Its anthers are almost devoid of pollen and the pistil is now pointing down, so that is easily rubbed by the bumblebee's back and then ready to be fertilised.

A bumblebee view of a foxglove. Note the open pistils on the lower, older flowers.

More information

Arthur A. D. Broadbent and Andrew F. G. Bourke (2012). The bumblebee Bombus hortorum is the main pollinating visitor to Digitalis purpurea (Common Foxglove) in a UK population. Journal of Pollination Ecology, 8 (7), 48-51.

Verboven, H., Brys, R., and Hermy, M. (2012). Sex in the city: Reproductive success of Digitalis purpurea in a gradient from urban to rural sites Landscape and Urban Planning, 106 (2), 158-164 DOI: 10.1016/j.landurbplan.2012.02.015

Horse chestnut scale insect

From April to July, tree trunks and branches in our street become mottled with Horse Chestnut scale insects. The bright white, powdery substance under the 'scale' is the ovisac, loaded with thousands of eggs. The scale is the dead body of the female, which has invested her effort into the production of the ovisac, after months of feeding on tree sap, and whose function is now protect the ovisac. The Horse Chestnut scale insect, Pulvinaria regalis, is an invasive species from Asia found in the early 60s and described from specimens in Paris in 1968. It is a generalist species, found mainly in urban environments and feeds on a diverse array of deciduous trees, and has a liking for Sycamore and Maples, Lime and Bay leaf tree.
  Scale insects do not look much like insects, do they? What we called scale insects are adult females, with flattened shiny bodies hiding tiny legs underneath, and piercing mouth parts like a shieldbug (scale insctsct are homopterans). Pulvinaria regalis has some mobility before egg laying. Both the first nymph instar (called crawlers) and adult males look more like a typical insect.
 Horse Chestnut scale insects hatch in summer and move onto the underside of leaves, where they feed.  Then, before leaf fall, they move back to the tree trunks and branches. In spring, mature males and females appear. Mature males are winged but do not feed, so they spend their short lives looking for females and mating. Females crawl to leaves, mate and start feeding on the tree sap and when fully mature and ready to lay, they move onto tree trunks to lay their ovisac. Although they can appear in such large numbers, they do not obviously cause much harm to mature trees, although saplings or weak trees may suffer from loss of sap. Scale insects, in particular eggs and nymphs, are the main food source for some ladybird species such as Exochomus quadripustulatus, the Pine Ladybird, no wonder they are also common on our street.

More information
GB non native fact sheets