HARVESTMAN
THERE are around thirty UK species of harvestmen and around twenty have been recorded in Nottinghamshire.
They are often encountered in our gardens and houses and are often assumed to be spiders.
They are Arthropods and belong to the same Arachnida class as spiders but are classified in the Opiliones order whilst spiders are grouped in the Araneae order.
The name Harvestmen is derived from the fact of being seen more in late summer and autumn coinciding with harvest time.
Like spiders, harvestmen have eight legs, but unlike spiders they don’t have a separate abdomen, and as such no waist, which is the easiest way to separate a harvestman from a spider.
Body length does not exceed 7 mm (0.28 in) although their long legs make them look much larger. Females are larger than males and juveniles look like smaller versions of adults.
Harvestmen do not have silk or venom glands and present no hazards to humans, and like scorpions, some species will glow under UV light.
Most species are nocturnal and generally brown coloured with a single pair of eyes in the middle of the head, oriented sideways. Typically, the second pair of legs are slightly longer than the other three pairs and are used as sensory organs in a manner like a blind person using a stick as their eyes cannot form images.
When attacked they can shed a leg which will grow back again. The discarded leg continues to twitch after it has been detached, typically for a minute although some have been recorded as twitching for up to one hour. It is believed that this leg twitching is a means to distract the predator whilst the harvestman escapes.
They tend to be omnivores and use their sensory legs to prey on small insects as well as eating plant material and fungi. After feeding they clean their legs by drawing each leg in turn through their jaws.
Following mating the male of some species will guard the eggs, often against their mate. Eggs hatch after 20 days and the resulting nymphs typically pass through six different stages (instars) before reaching maturity.
Eggs are laid in autumn and these hatch in Spring, although there is an indication that there are two generations per year in more southerly areas. The first adults appear in May, with numbers peaking in September.
Keep a look out for these small but very interesting arachnids and notice how different they are from spiders.
The Common harvestman Phalangium opilio is a common and widespread species and is distributed across Europe. It is reddish-brown on top and white below with quite prominent fangs. This species is active during the day and can be found in a wide range of habitats such as gardens, grassland, brownfield sites, open woodland, and hedgerows and typically in low vegetation but can also be found on tree trunks and walls where they feed on many species of small invertebrates.
In the US, harvestmen are referred to as ”Daddy-longlegs” but in the UK we tend to use this name when referring to a large type of cranefly; the gangly insect that always seems to find a way into our homes in the summer and autumn.