guard

Bees and butterflies have had a blog post to themselves, but here are a few other invertebrate encounters from 2017 I thought I’d share on the penultimate day of the year!

Wood Ants

These were taken in Great Wood in the Quantock Hills. We spent a while being amazed at the ability of these tiny creatures to pull twigs and other materials into position around their nests, joining others to give assistance where required or simply tugging with amazing tenacity until they got where they were going. Soon we also noticed the guard ants, who were trying their hardest to intimidate us into backing away and leaving the nest in peace!

Great Diving Beetle – Dytiscus marginalis

We came across this beast when doing great crested newt surveys in the springtime – the bottle traps used to catch and count the courting newts also work for other species such as this, one of our largest beetles. They can have quite a nip, so I’m told, so this one was handled with care before being returned to its pond in a pasture field.

Sawfly in a buttercup

I came across this little sawfly – its head dusted with pollen – settled in a buttercup flower in Muston Meadows in early summer. It didn’t move as I got into position to take a photo, and I could only assume it had settled there for the night.

Wasp – Gasteruption jaculator

This amazing looking creature was feeding on the fool’s water cress flowering at the edge of our garden pond. The amazing ovipositor is so much larger than the wasp itself which made it look for all the world like a radio-controlled insect as it flew between flowers!

Wasp – Ectemnius sp.

I came across this little wasp feeding on the hogweed flowers on a walk through Cheddar Gorge and thought it deserved a portrait – the rounded head with the eyes wrapped around looks as though it could have been the inspiration for a number of sci-fi aliens!

Ornate-tailed digger wasp – Cerceris rybyensis

I was walking through the Hills and Hollows above Grantham one afternoon and came across a series of holes in the bare earth – I watched a while and saw several heads peeking out before one of the insects arrived from outside and I could get a proper view. This is a species of digger wasp whose prey is bees such as this solitary bee held beneath its body. The wasps bring the bees back and pull them underground to provide food for their larvae.

Darter dragonfly – Sympetrum sp.

This dew-bejewelled dragonfly was resting on a flower stem in Muston Meadows in August. Taken just after sunrise, this shows the roosting behaviour where the dragonflies will find a safe place to spend the night, waiting for the sun to warm them in the morning and get them up to temperature so that they can take to the wing once more.

Snail

This little snail was crawling across the roof of my car when I got back from a dawn bat survey in late summer. I’m not sure how it made its way all the way there, but I liked the reflection in the early morning sunshine. I popped it back into the vegetation in the verge before heading home!

Wolf spider (Lycosidae)

This photograph was taken in the Grantham Hills and Hollows in late summer as the grasses were beginning to turn from greens to browns. I had bent down low to get a photograph of one of the wildflowers, and then my eye was caught by how many invertebrates were active just in the grasses beside it.

Grasshopper

This grasshopper was taken on the same afternoon as the wolf spider above – I’m afraid I haven’t attempted an ID on this little character but would welcome any suggestions! The camouflage of this grasshopper amongst the greens and browns of the aging summer grassland meant I only spotted it when it hopped to another location.

Minotaur beetle – Typhaeus typhoeus

This amazing beetle was trundling across a forest path in the Quantocks in autumn. Despite the fearsome looking horns, they are not predatory but are in fact a species of dung beetle which feeds on rabbit droppings amongst others. They nest in deep tunnels and will pull the dung back down with their powerful legs in order to provision the larvae.

I was intrigued to spot the nest of an European hornet – Vespa crabro – in an old haybale at a survey site recently. It was the middle of October and the weather was turning cooler and damper.

I was fascinated by the behaviour of the guards who were stationed at the entrance where hornets returning to the nest would land and enter. One individual was stationed to intercept each new arrival, touching antennae with them before either letting them pass or subjecting them to further scrutiny.

A hornet sentry stationed at the entrance to a nest built into an old hay bale

I can find little on this behaviour in hornets, but as a social hymenoptera, I hope that honeybees are a good parallel. The seminal piece on guard behaviour seems to be Butler and Free’s 1952 paper entitled The Behaviour of Worker Honeybees at the Hive Entrance.

In honeybees, the guards are drawn primarily from younger bees with older workers rarely taking the role. The role of guard is also not fixed – many also forage and will even be seen attempting to rob the nests of other hives. If the hornet system is the same, this would mean that one of many workers can take the sentry role.

In the paper, the Guard Bees are described as ‘assuming a very typical attitude, frequently standing with their forelegs off the ground, with their antennae held forwards and their mandibles and wings closed. Should they become even more excited they open their mandibles and wings and appear to be all ready to rush towards any intruder. Such excited guard bees watch the movements of bees flying overhead and approaching the hive, often jerking round to do so, and make intention movements to intercept any bee which they see to alight near them‘. This very neatly describes the behaviour I was watching, and is shown in the photograph below of the guard intercepting a new arrival.

The hornet sentry waiting to interrogate a new arrival on their return to the nest

The method of interrogation was through contact between the antennae of the two hornets – social hymenoptera have an advanced ability to distinguish between those within their colony and those outside – termed ‘kin recognition’. Some individuals returning to the nest showed almost no signs of interest in the guard and simply barged on in whilst others paused and interacted with the guard before being allowed entry.

The guard did their best to check their credentials and usually found them acceptable, but sometimes would follow a returning hornet into the entrance for further investigation.

Showing the guard hornet interrogating their nestmate

One or two individual hornets were not permitted entry, despite repeated attempts to gain it. They would be chased away across the face of the haybale by the guard, soon to return and re-attempt entry only to be denied once more. There may be several reasons for this. These rogue hornets could be individuals from another nest, or it could be that the guard was mistaken in denying entry to a member of their own colony. The system relies upon chemical signals, and is not perfect leading to errors through denying entry to legitimate colony members as well as sometimes accidentally allowing entry to non-nestmates.

The investigation in honeybees noted that intruders carrying a load of pollen were usually permitted entry whilst those without were more likely to be intercepted and turned away. This is perhaps on the assumption that robbers rarely come bearing gifts and so their arrival with resource suggests they can be allowed in. Other factors important in influencing guard behaviour was recent disturbance – if the nest was disturbed and the bees felt under threat, they were much more likely to examine newcomers, even those with a full load of pollen.

This is a fascinating fascet of behaviour and I have tried to piece together the likely story based on the research into the honey bee. If anybody can provide me with further information about this behaviour in hornets, I would love to hear from you!

Grantham Ecology

The wildlife of a small market town…

2017 in Invertebrates

Hornet Sentries