Ivy bees in Hull

 I have spent some time watching mature Ivies lately. It is Ivy peak flowering season, and the couple last days have been warm and sunny, bringing the insects out, the ivies humming with insect activity. Droneflies, Red Admirals, Comma, Wasps, honeybees are attracted to flowering bees. I was actually looking for Green Mesh Weavers, on an Ivy in an untarmaced tenfoot (alleys between houses) when I noticed two stripy bees rummaging around the leaf litter at the bottom of the ivy. I couldn't believe they were Ivy Bees, Colletes hederae! I have previously seen Ivy Bees in east Yorkshire, at North Ferriby and at Flamborough, but I thought we wouldn't get them in Hull due to our clay soils, as this bee needs loose soils for nesting. 

Two bees exploring the soil under the ivy, this is probably loose enough and sunny enough for a nest site?

A winner from climate change

Ivy Bees started colonising the UK from 2001, after expanding in northern Europe, and in the last couple of decades its distribution range has rapidly expanded northwards, with the first Scottish records coming in 2021. The mail pollen source for its larvae is Ivy, and the bee flight period coincides with the flowering season of ivy, from September to early November, with a single brood. They are solitary bees but they tend to nest together, sometimes forming large nesting aggregations in suitable habitat. Females will excavate a nest and line the walls with a cellophane-like substance, which explains another name of the bee, Cellophane Ivy Bee. Ivy pollen is brought to the nest and an egg is laid atop a mound of pollen, before the cell is sealed and another load of pollen is collected for the next egg.

One of the Ivy Bees near the ground after some exploring.

A female laden with pollen having a rest to clean its tongue.

A foraging female showing the banded abdomen. This bee is relatively large, the size of a honey bee, with orange hairs on the thorax, and contrasting broad buff bands in the abdomen, unlike its close relative the Sea Aster bee, which is smaller and has a white banded abdomen. Habitat, timing and foraging flowers can also help distinguish these bees.

Blue lace web spider portrait

I enticed some blue lace web spiders, Amaurobius similis, out of their retreats gently spraying their webs with water. They are shy spiders and might swiftly come inside when realising it is not prey, but some stay out long enough. The one above was one of several in ivy, where I find they are quite common. She looks lovely, both powerful and fresh. The one below, a much darker individual lives on the corner of my fence. Both are mature females, the size of a honeybee.

Loving the ivy

The late flowers of the ivy are a bug magnet in the autumn, when other sources of nectar are scarce. I have posted before on ivy fest season, but today I came across some new ivy visitors in a large ivy just starting to bloom in my local cemetery. Speckled Wood butterflies rarely visit flowers, as they usually feed on honeydew produced by aphids up in trees. So, I was pleasantly surprised to see two individuals feeding on ivy together with a Comma and many Droneflies.

Speckled Wood and Comma

Comma

Dronefly Eristalis tenax

Male wasp

Helophilus

Yellow dung fly?

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.

Tiny snails on cockle shells

My daughter found some tiny snails under a cockle shell in a pot yesterday. I took some photos but I could not identify them so today I went to find them again and try and take some shots of the more informative mouth of the shell. There were five or six of them, that were now active after last night's rain.

I looked in the pot and I found dozens of them. I had never seen them before and we had a whole pot population of these 2 mm or so snails happily living in the garden! Fauna, from WAB, identified my photos of the shell mouth today as Lauria cylindracea, a very common and widespread snail in the U.K. A favourite habitat is on stone walls covered on Ivy, but also lives in moss, leaf litter and crevices of old trees, habitats not particularly wet. It feeds on fungus growing on the dead leaves.
 As many snails, individuals of L. cyclindracea are hermaphrodites, which mate with each other to fertilize their eggs. This species, however, is relatively unusual for a snail in that it is ovoviviparous. It retains its eggs - 4 to 6 -inside its body until they hatch, and they are born into miniature snails, even tinier than their parents. Some of these juveniles were also present under the shell near the adults. The snails reach maturity at two years old and can live over 5 years, reaching a maximum size of a mighty 3.5 mm.

 In their study of life history and reproduction of L. cylindracea in Israel, Heller and collaborators discussed what evolutionary forces might have led to the evolution of ovoviviparity in this species. They hypothesize that a combination of small size - which limits the total number and the size of the eggs that can be produced - and high egg mortality, for example due to drought or lack of appropriate egg laying sites or inability to bury the eggs, are the key selective pressures. That way, offspring are born right next to their parents at the conditions most suitable for survival. The snails can also determine up to some point when the birth happen, retaining the juveniles longer when the conditions are very dry, and quickly giving birth when favourable moisture conditions return, that way maximising the chances of their offsprings survival. Heller and collaborators state:

Active hatchlings are advantageous, as compared to eggs, in that they can immediately start to feed, grow, fight off fungi, cope with brief periods of desiccation by moving into deeper layers of litter or temporarily retreating into their shell, and avoid drowning (or being washed away) as a result of occasional flooding of the riparian litter habitat, by moving into higher layers.

They compared this reproductive strategy in minute snails with the situation in larger species:

Large snails can produce eggs in vast numbers. Further, lack of size constraints enables the large adult to lay large eggs, generously coated with thick layers of albumin and mucus to tide the developing embryos over varying periods of drought and hunger. In Helix texfa, a species of 40 mm and 4.3 g (found in Israel very close to our present study site), each single egg averages 5.5 mm in size and 70 mg in wet weight (bigger and heavier than an entire adult Lauria), an adult produces 60 eggs per clutch, and clutch weight represents about 10% of body weight (Heller & Ittiel, 1990). In large snails with large clutches also sib cannibalism may occur, thereby increasing survival chances of the first individual to hatch (Baur, 1994). Further, large oviparous snails frequently deposit their eggs into pockets in moist soil. A deep cavity lined with mucus can protect the eggs against bacteria and fungi (Baur, 1994); it also enables the deposition of eggs in soil layers that remain damp for longer periods of time, and thereby reduces risks of desiccation. The cavity is dug out by the snail’s foot, so its depth is broadly correlated to foot size. Helix can dig 5cm into moist soil and Arclzachatina can dig a 15 cm cavity in one night (Tompa, 1984; Baur, 1994). Minute snails, however, do not have the potential to dig much beyond 0.2cm (except for subterranean genera, see Heller, Pimstein & Vaginsky, 1991). They can either dig minute cavities, or deposit their eggs in damp litter, where they would be exposed to fungi. Ovoviviparity may thus be a mode of parental care for snails that can neither lay many eggs, nor big eggs, nor dig deep egg cavities.

I will keep looking for these snails to see how widespread they are in the garden. I wouldn't be surprised to have overlooked these fascinating creatures due to their minute size. Were not for the white background of the shell where we found them we would have probably missed them altogether.

Reference
Heller, J., Sivan, N. & Hodgson, A. (1997). Reproductive biology and population dynamics of an ovoviviparous land snail (Pupillidae). Journal of Zoology, 243 (2), 263-280 DOI: 10.1111/j.1469-7998.1997.tb02781.x

Ivy fest!

The end of September is the time of the year when I like to visit an old ivy growing on a south-facing brick wall. Today was the first day I saw it flowering for good. Ivy (Hedera helix) is an unusual plant in that its flowering season starts with the beginning of autumn. Given the scarcity of alternative sources or nectar at a this crucial time of the year - when many insects are getting ready for winter dormancy, egg laying or migration, this marks a food bonanza for many insects, the final feast of the year. Drone flies (Eristalis) and green and bluebottles, hover-flies, wasps, honey bees, queen bumblebees, butterflies (Red Admirals, Small Tortoishells, Painted Ladies, Large and Small Whites, Commas) buzz on the green-yellow ivy flowers.

Myathropa florea

Helophilus pendulus

Syrphus sp.

Bluebottle, Calliphora vomitoria

Eristalis tenax

Above, an illustration of the diversity of hoverflies who use Ivy

Red Admiral

Comma

And all them must keep watch for garden spiders, who never say no to a juicy hover-fly...

By the beginning of December the Ivy flowers are gone and the berries start to grow.

 This is one of the last ivy blooms of the year, with a late red admiral (photo taken 30/10/2006):

The end of summer

Autumn is quickly approaching. The leaves on some lime branches are already yellow and a few brown leaves rustle on the ground. The squirrels have dropped some early conkers they have nibbled. But today is a bright, warm day, with lots of butterflies. A Speckled Wood was sunning itself in the park and a Comma, a Small White and a Large White visited the garden in the morning.

We walked past one of the last buddleias in good bloom. It is now the end of the buddleia flowering season and this particular bush teems with butterflies today. I count six Red Admirals (probably already migrating south) , three Small Tortoiseshells (ready to hibernate) and a Large White.

One Small Tortoishell fed on the dandelions amongst the grass.

Other insects included a queen Bombus lapidarius, velvety black and red feeding on Agapanthus, and B. pascuorum, the most common bumblebee these days, on Sedum spectabile (below).

Lots of Araneus diadematus. One five-legged male creeps close to a female's web.

Another female nearby spins its web.

The large ivy is not flowering yet, although it's got lots of buds.