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Geoff Oxford FAC T SHEET 11 Essential ha rvestman info Advancing Arachnology A l e x

H y d e

- a l e x h y d e . c o . u k

Harvestmen are an ancient group of spider-like animals with an array of defences, weapons and special tricks that could come straight from a Bond or Sci-Fi movie. What’s in a name? How to recognize a harvestman Harvestmen are so-called Although, like spiders, harvestmen are arachnids and have because they are more eight legs and a pair of pedipalps at the head end, they differ noticeable towards the end of summer, the traditional from spiders (see Factsheet 1) in several important ways: harvest time. Harvestmen Spiders The family containing A body in one part (head/thorax A body in two parts harvestmen is the Opiliones, /abdomen fused together) (cephalothorax and abdomen) meaning shepherd. In Roman times, herdsmen walked on Abdomen with segments visible Abdomen without segments visible stilts to watch over their flocks, so the family name Don't produce silk or make webs Characteristic silk production, alludes to the typical with web made in many species harvestmen’s long legs. Two eyes on a raised ‘turret’ Usually eight eyes, always at the A common name for (ocularium) front harvestmen is ‘Daddy long- Each chelicera (jaw) formed of Each chelicera a single piercing legs’ but beware, the same two parts like a lobster claw prong name is given to a spider No venom produced via Most species inject venom via (Pholcus phalangioides ) and chelicerae chelicerae to craneflies, which are No odoriferous glands insects. Odoriferous (stink) glands produce various noxious M a r chemicals c o

M c

G Genital operculum (flap) covers Genital organs consist of i n t y male penis or female ovipositor modified male pedipalp and female epigyne Leiobunum rotundum – (female) fragile but look closely and and moving rapidly across you’ll discover they have a vegetation and rocks. The What makes wide range of hard, pointed larger species have extra harvestmen bits – some very large – segments in their feet, variously called spines, making them incredibly so successful? tubercles and denticles. These flexible. Like monkey tails, Harvestmen have an make it difficult for predators they can coil round plant adaptable body form – simple to attack them front on. stems allowing them to move changes to the proportions easily through vegetation. and shape have allowed them Amazing legs and prehensile to evolve to meet the feet – Harvestman legs Chemical weapons – During demands of a wide range of provide an ideal platform for their evolution, harvestmen habitats and ecosystems. For suspending the small body have been exposed to all sorts A l

example, they vary greatly in e

x Impressive

H

their relative leg-lengths and y

d defensive e

- spikes around this reflects the different a l e

x the eye ’turret’

environments in which they h y

d of Megabunus e

live (see Where to find them). . c

o diadema . u

Their utilitarian design makes k them the Swiss army knives of the invertebrate world! Armour – Superficially harvestmen appear soft and N i k

H up and down, probably to u n Single t distract a woul d–be predator - Fossil harvestmen body The basic harvestman One pair part this behaviour rapidly spreads of eyes through the group. structure can be seen in fossils 400 million years Where to find them old, and they must have Harvestmen can live evolved millions of years anywhere from seashore to before that. Their features mountain summit as long as have been so successful they have access to a and adaptable that they reasonably humid shelter during the day. The small, have survived many Chelicerae millennia of changes to (jaws) short-legged species, with legs 1-2 times their body their habitats, predators, length, are adapted for living diseases and prey. in soil and leaf-litter, where they feed on snails. Those Pedipalps with medium-length legs are full of eggs. Both sexes have Phalangium opilio (male) usually found lower in the their genitalia hidden below a vegetation but range higher flap (operculum) between of bacterial and viral infections up as they grow. The long- their leg bases. This opens and have evolved chemical legged species, with legs up like an aircraft cargo hold protection to combat them. to 10 times their body length, allowing the male penis to be When released through their are usually found on humid extended and, after a fairly odoriferous (stink) glands, rock-faces and tree trunks in rudimentary courtship, droplets of these chemicals forests and gorges but some inserted below the front edge also help to deter predators are now also associated with of the female's operculum. through their nasty taste and human habitation. Subsequently, the female smell. extrudes her ovipositor from Disposable legs and group What's for dinner? below her operculum and protection – If a predator Part of the harvestmen’s seeks out crevices in soil and grabs a leg, the harvestman success comes from their below bark in which to lay her can detach it and make off on ability to use a wide variety eggs. Females of some the ones remaining. of foods, from fermenting fruit species can produce viable Meanwhile, the disconnected to soft-bodied invertebrates eggs without fertilization leg can twitch for several and carrion. They are able to (parthenogenesis) – a useful minutes, distracting the sip fruit juices and other fluids trick for species spreading to predator while the owner directly and can use their new areas.

claw-like chelicerae to tear D

escapes. In contrast to i l y s

apart solid foods. Like spiders a

immature spiders, n d

they part-digest food before T r

harvestmen can’t regenerate e v

sucking it up but they also o r

lost legs when they moult. P e

ingest solid food. n d l Some harvestman species e t o roost in sheltered places The next generation - n (e.g. under bridges) during the day, often in very large the harvestman numbers, and disperse to go mating game hunting at night. When a Harvestman males and group is disturbed, the nearest females look similar, with the individuals will start bobbing females slightly larger when Mass congregation of harvestmen