By James Duncan
Woods Mill Engagement Officer
There's little doubt that the European hornet, Vespa crabro, is a rather fearsome looking insect. But this ferocious exterior betrays a species that is in fact rarely aggressive. Unlike their infamous relatives, hornets are unlikely to disrupt your picnic. Their sheer size - between 2-3 cm's for workers and males, 3-4 cm's for queens - and riotous buzz can however make them an intimidating proposition. They're our largest and most impressive eusocial wasp species, displaying the very highest level of organisation of animal sociality and frequently more than doubling the size of our more familiar common wasp, Vespular vulgaris. Both belong to the order Hymenoptera, comprising bees, wasps, ants and sawflies. Woods Mill currently resounds to the frantic commotion of hornets - particularly at night. This is where they differ from other members of the wasp family, Vespidae. Hornets are attracted to light. This behavioural trait can leave them viewed with no small amount of trepidation. On warm autumn evenings there's little doubt they'll pay a visit if their nest is placed in close proximity to a well-lit dwelling. Many a recent Woods Mill moth trap has been plagued by them.
Hornets can of course potentially pack a punch. They harness a sting typical of their family group, though it's non-barbed and won't be pulled from the hornets body, unlike that of a honey bee. It's used predominantly in defence of the hive. The sting doesn't contain high levels of toxic species-specific compounds that tend to be wielded by invasive Asian hornets, and it's toxicity is on average lower than that of the honey bee, Apis mellifera. It is of course worth noting that stings can still trigger allergic reactions, and those susceptible to wasp venom will likely suffer the same from hornets. But the simple fact is that the European hornet is a docile creature, avoiding conflict and rarely displaying any form of aggression unless the nest is approached or the colony is threatened. It suffers from an undeserved reputation.
The hornet queens are the sole colony survivors of a UK winter and they emerge as the weather finally starts to warm in early spring. They waste little time searching for a suitable location for their paper-pulp nest, mixing saliva with chewed plant fibres to create a hardy cement. Though the hornets display an avid attraction to light, the nest site will be quite the opposite, most likely built in a darkened tree hollow or sheltered cavity, usually two metres or so above the ground. Queens lay eggs into individual paper cells which then hatch as infertile workers. Whilst these tend the nest the queen settles into life as an egg-laying machine. The nest expands throughout the summer with new queens and males emerging in early autumn, keen to mate after a 'nuptial' flight. Life is short for the males who quickly die off, followed a short time later by the original queen and workers. The newly mated queens will then search for a hibernation site, never returning to the original nest.
© Neil Fletcher
Only 60 years ago the European hornet was a rare beast in the UK, and it was only central southern England that harboured a population. In the last 30 years it's substantially increased its range, spreading both east into Sussex and Kent, and north towards Yorkshire. Unfortunately it's still much maligned in many areas of the world and is in fact locally endangered and even threatened with extinction in parts of Europe owing to the destruction of its nests.
Hornet dietary requirements are surprisingly varied and their substantial hunting abilities sees them capture a wide variety of invertebrate prey. Interestingly this prey is largely used to feed the growing brood, not the adults. In return for this supply, the larvae willingly oblige the adults by exuding a sugary liquid for them to feed on. They have a huge appetite for high energy food sources and can also be found feasting on tree sap, nectar, fruit and carrion. Hornets ultimately do a fantastic job in predating what are frequently regarded as both garden and agricultural pests. Their assistance in maintaining the natural balance of other invertebrates is no doubt a benefit and it seems a great shame that they themselves should be considered a pest. Their presence in a farm or garden should perhaps be welcomed with open arms.