Sunday, 27 June 2010

More on Fork-Tailed Flower Bees

I had a super A. furcata watching day in my local wildlife garden today. In a beautiful large patch of flowering Hedge Woundwort (Stachys sylvatica), in the shade, a male (below) kept patrolling, checking every flowering spear visually and darting between them, stopping to feed occasionally.
Two females collected nectar and pollen, at times both together in the same spear. The male came across and pounced a couple of times on a female, but I saw no copulation. Males seem to have a similar patrolling behaviour around favoured flowers as A. plumipes. In my garden it patrols different flowers around it (Iris, Digitalis lutea and D. purpurea). But last year I planted their local native favourite plant, S. sylvatica in a shady corner. Although it is still small, it is now flowering. Something interesting is that these bees do not mind shade or cloudy weather, they will be out and about like bumblebees whatever the weather, so they don't tend to overlap with sun-loving Anthidium manicatum - which has a similar flower choice than them and males aggressively defend territories - so much when they forage. I wonder if they are able to thermoregulate in a similar way than their relative A. plumipes and this allows them to exploit a different niche to other summer bees.
An Anthophora furcata female with legs full of pollen foraging in Stachys sylvatica.

National Insect Week Gallery

I have been too busy writing down stuff I've been watching or compiling records, and generally watching bugs these last warm days to blog, but I have decided to put an end to this by celebrating National Insect Week (21-27 June) with a gallery of the bugs I have been watching. I hope you enjoy them.
Flies: This is a large hoverfly, Vollucella pellucens. I have been watching them today hovering and I tried in vain to get a good shot in flight. This one posed nicely for me though.
 Bees: I had a great time watching Anthophora furcata in my local wildlife garden. This female is gathering pollen from Stachys sylvatica.
 Butterflies: the first ringlet of the year. It was warm and this individual fluttered for quite a while before settling on the grass.
Moths: yesterday I spotted this Narrow Five Spot Burnet atop a Knapweed seed head.
And more bees: After cutting a piece of Circaea luthetiana, this female Leaf-Cutter Bee (most likely Megachile centuncularis) had to retreat and alight again as it couldn't fight the wind carrying the piece of leaf. After a while, it flew away to her nest.
A sunbathing Wool Carder Bee (Anthidium manicatum) female.
Beetles: A female Lesser Stag Beetle walking over some plants on a front garden yesterday. So far, I have only seen females in Hull.
More bees: A Bombus hortorum extends its long tongue before landing in a Digitalis lutea flower. This is the longest-tongued bumblebee in the UK.
A male Colletes daviesanus resting on an Oxeye Daisy flower and...
a female with loaded pollen baskets nearby.
To end, another bee (of couse) a female Anthidium manicatum feeds on a Geranium flower on the summer solstice.

Wednesday, 16 June 2010

Daddy long legs vs bath spider

I got this shot yesterday, having missed the action under the kitchen units. A Daddy long leg spider (Pholcus phalangiodes) holding a Tegenaria (the common 'bath spider') well secured with lots of silk. Judging by the prey residues I come across, Pholcus often hunts spiders - and woodlice. I have never seen them hunting through, they mostly sit patiently on their corner, waiting for prey to bump into them.

Tuesday, 15 June 2010

Flies on costume

A Bombus lapidarius flies by, and stops to sunbathe on a leaf...but, wait a minute!, bumblebees industriousness clashes a bit with this behaviour, and I have a second look. Doh! it's not a bumblebee, but a mimic: the large, colourful and furry hoverfly Merodon equestris. It is easy to be fooled. This individual is all black, with a bright red tail. The costume is so good, you can't stop watching: even the back femur is thicker like its mimicking the bee's pollen baskets! And it gets more fascinating still: Merodon equestris is highly polymorphic and different individuals colour patterns mimic different bumblebee species. Earlier in the month I came across one looking like Bombus pratorum and another like Bombus pascuorum. The different forms are actually just colour morphs that interbreed with one another, as shown in one of the photos below. Some of the colour patterns are sex-specific, that is, they are always male or female (the 'lapidarius' looking form is always a female). This fly can be found from April to September, but it is most abundant in May-June. The species is native from southern Europe and is thought to have been introduced in the UK from the continent - where it was first recorded in 1869 - in shipments of flower bulbs, on which the larvae feed, hence its common name, Large Narcissus Bulb Fly
Imitating Bombus pratorum
This male looks a bit like B. pascuorum
Two colour forms mating on the side of a pot.

Monday, 14 June 2010

Ants as scavengers and herders

So far I have overlooked two important aspects of garden ant foraging behaviour, mainly due to the lack of suitable photos. Yesterday, I spotted a strange large insect walking on the concrete yesterday, when I got closer I realised it was actually a dead bluebottle being dragged by a garden ant (Lasius niger). Another ant run frantically back and forth, but a single one seemed to do most of the work. The strength of an ant is quite formidable, able to lift or drag objects much heavier than themselves. This illustrates the role of ants as scavengers. Any dead animal will either be dragged to the nest or bits of it will.
The second aspect is one of the most surprising of ants - showing their adaptability -  but also a reason why they are hated by many gardeners: their role as aphid herders. Ants behave as farmers with their aphids and will try to keep the numerous aphid predators at bay as well as milking their honeydew. This is considered a mutualistic relationship and aphids also benefit from the behaviour. Even when aphid predators are excluded, aphids multiply faster in the presence of ants. The photo, taken today, shows two garden ants stimulating Elder Aphids (Aphis sambuci) to excrete their honeydew. Elder aphids form very compact groups on tender growing stems of Elder.

Friday, 11 June 2010

Cuckoo spit and froghoppers

The lavender bushes are still far from bloom, but they are covered on the decorative white froth blobs produced by the common froghopper or meadow spittlebug, Philaenus spumarius. The spittle-like foam (widely known as cuckoo spit in the UK) hides green nymphs which suck on the plant sap safe from predators and dessication.
 I uncovered the soft-bodied, green nymphs this morning by gently spraying the spit with water. Three were hiding in a quite large spit, head down, nestled in the joint between leafs and stalks, so that they resemble plant buds. In the afternoon they were covered again in the spit. To make the spit they mix air with their watery deyections and a surfactant secreted by abdominal glands using their legs, and they rest head-down, the spit rapidly covers them.
The adult - said to rememble a frog - is found from June all through the summer and until the first frosts.  It has powerful rear legs and is able to jump long distances - hence the 'froghopper' name and it is is found in the same places as the larva. The following photos, from July 2007 illustrate the large colour variation of the adults, with have similar feeding habits as their sessile nymphs, but with a very different, much more active lifestyle.

A review of Philaenus spumarius life history indicated that there is no less than 16 colour forms, and a lot of research has been devoted to the genetic basis of this colour polymorphism.
More information:
Yurtsever, Selcuk (2000). On the Polymorphic Meadow Spittlebug, Philaenus spumarius (L.) (Homoptera: Cercopidae). Turkish Journal of Zoology, 24 (24), 447-459. here.

The footballer hoverfly

With its yellow and black stripy thorax and brightly marked abdomen, Helophilus pendulus is a handsome hoverfly. It is also easy to photograph, as it likes to rest on leaves or the edge of pools and occasionally it can be seen feeding on flowers. This is the most common of a group of closely related species, some of them migrants and some found as north as the Arctic. Their larva are of the long-tailed type and are aquatic, found in small bodies of water with abundant organic material, where they feed. They have also been recorded in cow dung. I have found the adults from April to October. Today, an adult patrolled around a puddle on the pavement on a sunny spell after the last rainy days.

Tuesday, 8 June 2010

Leaf-cutters: Not braving the wet weather

It has been a colder, very wet last few days. Bumblebees have been quite active, sometimes even during rain, their internal warming abilities allowing them to keep foraging at lower temperatures. The sun-loving leaf-cutters were not active through. On sunday, I spotted a male Megachile willughbiella, hiding in one of the holes of the bee hotel. His pale moustache and 'gloves' being very apparent in the dark hole (top). Yesterday, I came across a cold, wet and drowsy female sitting atop an Allium head, while Bombus pratorum bumblebees fed on the same flowers. She was still there today.
This evening, even the bee hotel was getting too wet. There was a damp patch around the hole where the male was hiding, and he was looking quite bedraggled. Slowly, he crawled outside the hole, looking for drier room, and probably wishing for sunnier times.

Pollen gathering face brushes

ResearchBlogging.orgMost non-parasitic female bees collect pollen as well as nectar to provision their brood cells. Pollen is brushed from the plant anthers using their front legs and stored on specialised structures on the bee body or legs. Some bees, however, specialize on collecting pollen from flowers with raised anthers, which touch over the bee's head or thorax when bees land on them. These are called nototribic flowers and include species from the Lamiaceae (the mint family) and Scrophulariaceae (the figwort family). Although bee-pollinated plants benefit from bees taking nectar - exchanging nectar for inadvertent pollination - they do not benefit when potential pollinators efficiently gather the pollen for their offspring consumptions instead. Nototribic plants in response to specialised pollen gathering by bees, have flowers that make pollen hard to collect, even when they have plentiful nectar. Only bees equipped with either specialised behaviour or morphological modifications, or both can effectively make use of their pollen.
 Mueller found that only 13 species of Central European bees (including Anthophora furcataAnthidium manicatum and Osmia caerulescens) possess specialised structures to brush and collect pollen from nototribic flowers. In several of these species the specialisation is on the face of the bee and consists on a think covering of peculiarly shaped hairs, of wide bases and sharply bent ends. These specialised hairs seem to have evolved independently several times as the bees belong to different genera also containing species lacking such modified structures.
A photo of Anthophora furcata clypeus (top lip of the bee) and on the right a portion of it showing the specialised hairs (from Mueller 1996).

One of such bees, Anthophora furcata, the Fork-Tailed Flower Bee is a summer bee, active in June and July in the British Isles. These are long-tongued, relatively specialised species, which collects pollen mostly of Lamiaceae (and to a minor extent of Scrophulariaceae) flowers. They are often present in gardens where they feeds on Lavender, Tree Germander and Lamb's ears (Stachys byzantina) as well as foxgloves. A couple of males I spotted yesterday, the first of the year, were feeding on a patch of Stachys sylvatica, and the photo of one of them on top of the post shows the position of the top lip of the flower - which hides the stamens and pistil - touching the bee's head. 
Mueller also investigated the brood cell contents and pollen load of bees to ascertain the degree of specialisation of the bees and also looked into the actual bee's behaviours to gather the pollen to account for the position of the facial hairs. In the case of A. furcata:

[it] presses its head against the anthers and, by vibrating its indirect flight muscles, buzzes the pollen amongst the transformed hairs. No further head movements can be observed.

The 'buzzing' releases the pollen from the anthers, and the specialised hairs help retain the pollen grains on the face. The bee then removes the pollen grains adhering to the specialized pilosity by rapid stroking movements of the forelegs in flight after leaving the flower.
Female of A. furcata feeding on Lambs ears.
Although the bee behaviour could be thought as a form of 'pollen robbing', pollination can still take place while nectar sucking, as the pistil of the flower still touches the bee's thorax, making no contact with the specialised brush on the bee's face and the flower constancy of the bees makes it more likely that she will be carrying some of the same species pollen on her back.

More information
Muller, A. (1996). Convergent evolution of morphological specializations in Central European bee and honey wasp species as an adaptation to the uptake of pollen from nototribic flowers (Hymenoptera, Apoidea and Masaridae) Biological Journal of the Linnean Society, 57 (3), 235-252 DOI: 10.1111/j.1095-8312.1996.tb00311.x