Easy to identify and a downright astonishing lifecycle – conservation officer Mariko Whyte takes a closer look at one of our most intriguing native insects

Of the UK’s eight native oil beetle species, three are now extinct and three are extremely rare. All are under threat, suffering dramatic declines due to changes in how we manage the countryside, as their fate is intertwined with some of our most important native pollinators.
The most common species, the violet oil beetle (Meloe violaceus) and the black oil beetle (Meloe proscarabaeus) are found across Dorset, and are widespread throughout Britain. Up to 30mm in length, both species are black, often with a bluish metallic shine. Despite the names they are not easy to tell apart! Unusually among beetles they are flightless, having reduced wing cases, a sausage-like segmented body and long antennae.
The oil in their name refers to a noxious orange fluid exuded from their joints when they are threatened, repelling predators.
The oil beetle’s way of life is just as odd as its appearance, inextricably linked with certain species of solitary mining bees. Sharing the same flower-rich habitats as their associated bee species, black oil beetles are found mainly in grasslands while violet oil beetles are commonly found in woodland.
Adults emerge from the ground in spring and can be spotted bumbling around on sunny days between February and May, grazing on vegetation and seeking a potential mate. Males have modified segments in their antennae which they use in courtship to clasp and stroke the female’s antennae (presumably to get her in the mood).

Bee parasites
The female lays batches of about 1,000 eggs in shallow burrows dug in loose, warm soil – laying an astonishing 40,000 eggs in her short two-month lifespan. For black oil beetles, the eggs hatch into active earwig-like larvae within a few weeks, with thousands of 2mm orange triungulins (the baby beetles) scrabbling to reach the top of nearby flowers, scurrying with frenetic energy. Then they wait for passing insects to grasp onto.
Violet oil beetle triungulins are black and don’t emerge from the ground for a whole year after eggs are laid, so they are active earlier in the spring, overlapping with the adult generation.
The oil beetle larvae are effectively parasites of mining bees, hitching a lift from the flower to the bee’s nest. Once inside, the triungulins feed on the egg and pollen stores of their host and quickly moult to more typical grub-like larvae, eventually pupating and overwintering as adults underground before emerging as a new generation in the spring.
Visit dorsetwildlifetrust.org.uk to learn more about Dorset’s beetles.

The colour-changing flower crab spider hunts among the summer blooms: they fascinate ex-arachnophobe wildlife writer Jane Adams

I’m watching a spider on a flower, in the garden. The bloom of the pink allium resembles a lollipop perched precariously atop a wobbly bare stick. From the four bulbs I planted last autumn, there are now four perfect spheres, each one covered in bumblebees, honeybees and hoverflies. The spider, more precisely a flower crab spider, has set up shop on one of these blooms.
For years, flying insects have fascinated me. Their artful flight and tuneless buzzing are the essence of summer days and warm, soothing sunshine. But I am also fascinated by arachnids.
Not that long ago, I had an irrational fear of them, and would run a mile if ever I saw one. However, over time (and a lot of close-up photography), I have grown to love them.
The only complication is this particular spider also has a love of my favourite flying insects…

Some party trick
Flower crab spiders, or Misumena vatia, are common in gardens throughout the south. The Latin term ‘vatia’ means bent or curved, and as I watch this spider, she sits motionless with her powerful crab-like front legs ready to pounce: I’m mesmerised. Unlike many species of spider, the crab spider doesn’t make a web. Instead, she excels in the art of ambush. If and when she catches something, she will immobilise it by injecting digestive enzymes into its body with her fangs, before eventually sucking out its bodily fluids.
I know, I can hear you now. Ewww! How on earth can you love THAT?
Maybe love is too strong a word, but I definitely admire a transformative trick she keeps up her hairy sleeve. The female flower crab spider has the remarkable ability to perceive and see colour, and she can adapt and change the colour of her own body. This unique skill means she can blend seamlessly with the flowers that attract the highest number of prey. Admittedly, it can take her a while to change her shade – usually between ten and 25 days – but by secreting a liquid pigment into her body’s outer cell layer, she can morph from white to yellow, pale green… or even pink.
Imagine that as a party trick.

Flower crab spider facts:

Size: Female 5-9mm Male 3-4mm (the female will eat the male before or after mating, if he isn’t quick to escape!)

Eats: Flies, bees, butterflies, grasshoppers and moths

Find them: On garden and wild flowers from May to August (but you may need to look hard to discover them!)