Note the characteristic elongate legs, fusion of the body regions into a single unit, and external segmentation. Click/double click image to enlarge.
All 235 of the North American species, and all 5.000 of the species found worldwide, can easily be differentiated from spiders based on the fusion of the two body regions that appear as a single body region, as well as clearly delineated external body segmentation.
Unlike spiders, harvestmen lack venom as well as fangs of any sort. The pincerlike chelicerae are flanked by short pedipalps, which are sometimes mistaken as a fifth pair of legs. Harvestmen prey on a variety of microarthropods. Many also scavenge, while others feed on plants, fungi, fruit and sap.
Unlike spiders and other arachnids – such as scorpions, wind scorpions,(solfugids), whip scorpions, ticks and mites – who have to liquefy their food before consuming it, harvestmen directly ingest small particles of food.
The elongated second pair of legs function like antennae and are sensory, used to smell and detect all chemical aspects of the world around them. Harvestmen are unable to function well and will die shortly after the loss of both of the second legs.
Defense is primarily chemical , though they can practice self-amputation of legs if necessary.
Close-up of the body. Note the obvious simple eyes, set on raised turretlike bump. Click/double click to enlarge.
