7 spot ladybird

Yesterday there was a gap in the 31dayswild theme this month, but not to worry, it wasn't so much due to my inability to see and photograph a suitable invertebrate, but more to the overabundance of them as I visited a local nature reserve, but you may want to go to my Wild at Hull blog to find out. So, continuing in today's stormy day 7, I bring you a fresh 7 spot ladybird. Despite the abundance of Harlequin ladybirds in the garden, 7 spots seem to be having a good season and I have seen them regularly this year. This one was giving this knapweed bud a good check for aphids.

A bumper year for 7 spot parasites?

In the last few days I have found quite a few 7 spot ladybirds parasitized by the wasp Dinocampus coccinellae in the garden: live ladybirds snared to a silky cocoon underneath them. Today I did a quick count and found eight. You can see their portraits on this post. This is being a successful year for 7 spots: there are so many around it is hard not to get one or two ladybirds in the background of any bug photo I take! It is no surprise that ladybird parasites are enjoying this ladybird bonanza. If you want to find out more about the rather gruesome Dinocampus life cycle click here.

One on sage

on the conservatory frame

a second one on the spurge

one under a Lamb's Ears leaf

An odd one, with the cocoon on one side on a bougainvillea leaf in the conservatory

one on an orchid in the conservatory

a second one on sage

Dinner of the green bug muncher

After the very rainy April we are having a teasel growing in the garden is looking very luscious. It has grown a large rosette of leaves, and developed two large leaf-cups which are filled with water to the rim. If you want an account on this fascinating carnivorous plant, check here. I had a peek a couple of days ago to check if any drowned invertebrates were visible. And there were indeed! On the bottom cup (above) a 7 spot floated on a very cloudy liquid, while on the top one, a drowned slug was visible at the bottom of the clearer water, and a few small unidentified insects. What a catch!

Do spiders find ladybirds distasteful?

 I witnessed a curious interaction today. A 7 spot ladybird was walking up a wall, when a sudden movement caught my eye. It was a large spider, a female Amaurobius similis that had dashed out of her burrow in a hole in the wall, probably alerted by the pull of one of the silk threads that radiate from her burrow. She had caught the ladybird by one leg. The ladybird struggled to free itself, but she need not fight much. After a few moments, the spider released her grip, turned round and retreated into her burrow. The spider obviously had assessed the ladybird and regarded it not suitable for a meal. I doubt it was due to the ladybird size or strength, as Amaurobius are powerful spiders, able to subdue large flying insects such as droneflies and honeybees. The other possibility is that the spider has tasted the alkaloid rich liquid that constitutes ladybirds chemical defence mechanism and that is released from their leg joints when alarmed (the 'blood reflex'). I have previously seen dead ladybirds wrapped on silk caught on the webs of two spider species (garden spiders Araneus diadematus and the false widow Steatoda bipunctata). Indeed, field surveys and experiments carried out by John Sloggett showed that A. diadematus does trap and consume ladybirds, and is apparently immune to the toxic effects of ladybird's chemical defences. In contrast, other spider species do seem to find ladybirds distasteful, so this is a strong possibility for Amaurobius.

Another view of the interaction, not as sharp, but it shows clearly how the spider's chelicerae are pulling and lifting the ladybird's front right leg.

For other spiders, however, ladybirds are not even considered a food item. Take this little wolf spider, enjoying the company of the 7 spot ladybird a few days ago. Both individuals were sunbathing next to each other most of the morning. The spider popped in and out, paying no attention whatsoever to the ladybird.

More information

Sloggett, J. (2010). Predation of ladybird beetles by the orb-web spider Araneus diadematus BioControl, 55 (5), 631-638 DOI: 10.1007/s10526-010-9291-0

Unexpected pollinators

One of my spurge plants is in full bloom now. Spurges have complex flowers with exposed nectaries, which are available to insects lacking a long tongue, although they appear not to be very appealing to bees and butterflies. They attract bluebottles, hoverflies, ladybirds and wasps. Later in the season they will be taken over by ants, which will defend them aggressively from competitors. In the last few days, dozens of 7 spot ladybirds have been enjoying this early nectar, in the company of bluebottles and hoverflies. They pay back the plant by acting as its pollinators. Some of the ladybirds were covered in pollen and the one on top seems to be pushing up the plant pistil, so the anatomy of the plant is right for ladybirds to act as pollinators

This 7 spot ladybird, from 2/04/11 was laden with spurge pollen

Bluebottle enjoying the nectar

More 7 spots on the flowers, and possibly a harlequin

A little hoverfly, Meliscaeva auricollis

More awakenings

 The early spring temperatures continued today. Ants were scouting out of their nests, sage leafhoppers were active and honeybees and droneflies enjoyed the Laurustinus. I waited until the bee and the dronefly visited the same inflorescence to take the above shot. I wonder if the Laurustinus flowers change colour when they are pollinated, in the same way as the Horse Chestnuts, white when fresh and turning red when already pollinated and stop producing nectar. 

We counted over 100 7-spot ladybirds in the garden. Some were eating aphids on the spurge.

The entrance of the burrow of a large Amaurobius spider under a garage roof. If you click to embiggen you can see the remains of a wasp a Harlequin and some wings I cannot identify, possibly from bluebottles.

A green shieldbug, Palomena prasina, on its dark winter attire came out of its overwintering refuge.

 Wolf spiders enjoyed the sun on the sunny side of the garden.

Waking up to served breakfast

 I ventured out to the garden today despite the wind and occasional shower. Plants are starting to awaken: leaves sprouting, two daffodils about to open and a single bowed down Hellebore flower. 7 spot ladybirds like to hibernate between the waterproof leaves of the spurge and today the bright sun woke some of them up. They must have felt very lucky, as colonies of aphids were sitting on the very same shoots. I didn't see any eat aphids, in fact the aphid in the photo below was sitting on the ladybird's head just before I took the shot. But give them time and the spurge might be cleared up of aphids. Something I found surprising is that the aphids are reproducing, and it is february, weren't they supposed to be eggs at this time of year?

Twelve bugs of Christmas

Today we woke up to a mild, sunny day and I was pleasantly surprised by the diversity of active bugs about. I made a count of species and when I got to twelve I was reminded of the traditional carol and made up a buggy version:

12 ladybirds walking | 11 winter-gnats dancing |10 honeybees buzzing |9 bluebottles basking | 8 leafhoppers leaping | 7 woodlice hiding | 6 hoverflies flying | 5 snails sleeping | 4 spiders weaving | 3 harlequins | 2 drone flies | and a bumblebee on ivy

The honeybees in the local wildlife garden were coming out tripping over each other and ladybirds (7 spots mostly but also harlequins and 22 spots) were awaken by the mild temperature. I counted 5 spider species outside (Tegenaria, Zygiella, Pholcus, Steatoda, Linyphia). The main surprise was the bumblebee worker, extremely fast and active and with pollen baskets full with pollen.

Here is a slideshow of bugs seen and photographed today

Leaf sleepers

This is a good time of year to search for bugs in the leaf litter. On the top layer, ladybirds are set for the winter in the cosy, dry folds of the fresh fallen leaves. They usually cuddle up close to other ladybirds of the same species to overwinter, but it is not unusual to see two species together, like the 22 spot and 7 spot above. If you search a bit deeper on the soil, you can find centipedes, earthworms, and woodlice. With the colder temperatures, they are more torpid than usual, and then easier to photograph.

A shiny woodlouse, Oniscus asellus

Centipede, Lithobius forficatus

 A group of 22 spot ladybirds inside a vine leaf

Arion sp. slug

7 spot ladybird and birch shieldbug

Queens, harlequins and admirals

The last mild, sunny days of autumn are bringing out scores of insects. Standing under a large flowering ivy today the sound of buzzing bees, bluebottles, droneflies and wasps was extraordinary, especially given that November is only a couple of days away. Yesterday, six red admirals sunnied and gorged themselves on the ivy blossom. They are charging batteries before their migration to South Europe and North Africa.

Red Admiral and passing droneflies on ivy

 A green shieldbug, Palomena prasina, climbing a tree.

 Today, a queen Bombus hypnorum fed on lavender flowers. 

 A female Araneus diadematus spider sat proudly on her silky egg cocoon. 

Honeybees on ivy flowers

Dozens of harlequins and 7 spot ladybirds flew about landing on a sunny wall and leaving again.

Ready for winter

Only a couple of weeks ago, 7 spot ladybirds were mating. Today we found this little cluster, with a harlequin trying to merge in, nestled on a wall, ready for winter. More BugBlog ladybird posts here.

Mating 7 spots on 9/10/11.

Loving the fruit

Our apple and plum trees fruit in August, and there are many bugs that love them, some quite surprisingly. Slugs, springtails, woodlice and fruit flies gorge on fallen apples, and comma and speckled wood butterflies feed on blackberries, but recently I noticed a few new characters in our produce. Seven spot ladybirds clustered on overripe plums (we were away and failed to collect them) and honeybees and wasps joined them. The common wasp (Vespula vulgaris) above, kept coming back to feed on a damaged spot on this fallen apple. Sweet, sweet fruit!

7 spot ladybirds and a wasp

honeybee in plum

Dropping aphids and their alarm pheromones

Fortunately for the organic gardener, aphids have many predators: hoverfly larvae, lacewings, ladybirds, shield bugs and spiders eat them in numbers. Although aphids appear defenceless against their predators, they have evolved a suite of antipredator responses. Some aphids have warning coloration and sequester chemicals from their feeding plants that are distasteful or toxic to their predators, other release toxic chemicals or waxes and a few have a hard-skinned soldier caste to defend the colony, yet others maintain an army of ants that defend them. The most common form of defence - both against predators or parasitoids - is however, behavioural: the aphids move away or drop from the leaf they are feeding on when they sense an approaching predator.
 Dropping is very effective in reducing immediate risk: aphids fall away from the approaching danger onto the ground. Once there other costs become apparent: the aphid may be far from the host plant and is exposed to ground predators or to desiccation.
 The orange tree in my conservatory is infested with aphids. I took advantage of the abundance of 7 spot ladybirds in the garden and brought a few onto the tree, placing them on particularly infested branches. I was pleasantly surprised by the eagerness with which the ladybirds took to the intended job. They started munching aphids straight away, clearing whole shoots in a few minutes. After a little observation, however, it became apparent that it was the aphid's behaviour which was mostly responsible for the shoots being cleared. The undisturbed aphids sat motionless, on a living carpet feeding on the tender leaf sap nearby. In contrast, as soon as a ladybird attacked, the aphids on the same leaf came alive and some started to move away, going into another leaf, while many aphids dropped to the ground as the ladybird fed on their unfortunate siblings. The following two photos illustrate this. They were taken about 27 seconds apart. In the first one, notice the three aphids on the tip of the leaf. In the second photo, these aphids have dropped to the ground, leaving just a couple of aphid molts stuck to the leaf tip, while the ladybird is still feeding on an aphid, motionless.

 Ladybirds are very effective at eliciting the drop response from aphids, especially when compared to smaller, less energetic feeders, as demonstrated in experiments by John Losey and Robert Denno on pea aphids feeding on alfalfa exposed to a predator insect.

This means that on average 60% of aphids feeding on a plant stem dropped to the ground when a 7 spot ladybird (Coccinella septempunctata) was introduced, in sharp contrast to the lower dropping response to the bugs and the control. Given the higher mortality of aphids on the ground, it follows that ladybirds would be very effective clearing aphid infestations through direct predation, and their indirect effect on aphids dropping from the plant.
 What mechanisms are responsible for this dropping behaviour? or, put differently, how do aphids sense that a predator is approaching? Dropping behaviour happens in response to predator contact, vibrations generated by the predator, or in response to an alarm pheromone secreted by individual aphids when attacked. This chemical signal, (E)-ß-farnesene (EBF), is secreted in dropplets by the cornicles, little tubes at the rear of the aphid, and they may impregnate the predator, which in its next move will elicit the dropping response before actually attacking another aphid.
 The release of an alarm pheromone by an individual that is likely to be eaten by a predator seems paradoxical. What benefit can this individual gain from its production? An alarm pheromone can be adaptive when the benefit is shared by relatives. This is indeed the case in aphids: groups of aphids feeding in close contact are likely to be members of the same clone, that is, they are genetically identical, as aphids often reproduce parthenogenetically. The alarm pheromone also has longer lasting effects benefiting the individual relatives, as the aphids that have been exposed to the chemical tend to produce winged offspring, which will likely disperse away from predators, in the case of the ladybird attacker, they will be likely to avoid the following generation of ladybird larvae.

References
LOSEY, J., & DENNO, R. (1998). The escape response of pea aphids to foliar-foraging predators: factors affecting dropping behaviour. Ecological Entomology, 23 (1), 53-61 DOI: 10.1046/j.1365-2311.1998.00102.x
Schwartzberg, E., Kunert, G., Stephan, C., David, A., Röse, U., Gershenzon, J., Boland, W. & Weisser, W. (2007). Real-Time Analysis of Alarm Pheromone Emission by the Pea Aphid (Acyrthosiphon pisum) Under Predation. Journal of Chemical Ecology, 34 (1), 76-81 DOI: 10.1007/s10886-007-9397-8