When I was a child, we called these creatures "daddy longlegs spiders." But they are not spiders at all - they inhabit their own order, the Opiliones. There are, indeed, true spiders (order Araneae) that are called "daddy longlegs", but those are spiders of the family Pholcidae, aka cellar spiders or vibrating spiders. The Pholcidae are venomous, the Harvestmen are not.

Unlike the spiders (order Araneae), the abdomen of the harvestman is divided into segments, but it has no "waist". Instead, the head, thorax and abdomen are grown together into a compact, oblong body. They do not spin webs, or use silk or build nests. On top of the head is a black "turret", a knob with a tiny eye on each side. I know from watching their evasive actions they can detect me moving from 6 feet away.

Underneath is a pair of pedipalps, pincers used to grasp, tear and stuff food into its mouth, to fight other harvestmen, and to frequently clean its legs. Those seven-jointed legs are unique. If we had legs in proportion they would be 40 feet long. The second pair is the longest - about 2 inches - and their sensitive tips are used to explore, search for food, and warn of danger. The fourth pair is next in length and the first pair is shortest, and supposedly they can all be regenerated if lost or damaged; although I so frequently see these guys missing one or more legs, I have to wonder, "How long do these things live, they have time to grow new legs?" Besides, they seem to get around fine with six or seven.

About 1,900 species of harvestmen are distributed over the world in forests, fields and other land habitats. They can and do walk on water. We have 60 or more species in North America and the adults of all but one of these die with the coming of winter. They mate in late summer and autumn. While the smaller male drives away rivals, the female lays a few eggs at a time in the soil, or in or under rotten wood. This is repeated until she becomes merely an empty shell. In spring the newly-hatched young are white miniature editions of the adults. They soon darken and, as they grow, shed their skins like many insects do. Harvestmen are omnivorous, and thrive on decaying organic matter of every variety.

There is an old wives' tale about the daddy longlegs being the "most  venomous spider on earth", but the "fangs" are too short to pierce human skin. The harvestmen have no venom or venom delivery system, hence are completely harmless to man.

Odiellus pictus - Eastern Pennsylvania