Friday, June 19, 2009
Father’s day is nearly here so it seems opportune to spend some time with a daddy creature. Father’s day this year coincides with the summer solstice. Somewhere in the length of the day,
spare a moment to ponder the wonders of the Daddy Long-legs. On a shorter day you may not afford the time for something like that.
Did you know that there are hundreds of species of Daddy Long-legs – around 5,000 species worldwide and at least 200 species in North America? Some species are quite common and easy to spot in our yards and gardens, but I have chosen one of the smaller ones to make a point about the diversity within the order. Also, this particular one stands very tall, not in an absolute sense of course, but in terms of its posture relative to many of the other species. This trait made it particularly suitable for a day when we honor our fathers.
Name: Daddy Long-legs is the common name for all of the species of a large group of arachnids in the order Opiliones. They are collectively referred to as Opilionids. The word comes from the Latin opilio which means sheep-master or shepherd. The story goes that old-time shepherds roamed the fields on stilts using their elevated position to better locate and count their sheep. In England, Daddy Long-legs are still sometimes called shepherd spiders but they are known by different names in different places. In Indiana they are almost certainly known as Hoosier Daddy Long-legs. Harvestmen is another common name that is becoming more widely used. It refers to the abundance of the species during the harvest season. It is a less confusing name than Daddy Long-legs because it is used exclusively for Opilionids. The Daddy Long-legs name is sometimes used for cellar spiders (Pholcus phalangioides) and even for long-legged crane flies.
Caddo agilis: The chosen species for today is Caddo agilis where Caddo comes from the native North American people of the same name. Daddy Long-legs in general are found all over the world but the Caddo genus is known only in northeastern North America. The species name, agilis, is probably a reference to its nimbleness. It can move quite rapidly relative to many other Daddy Long-legs.
When and where seen: Daddy Long-legs are common but not all of them are easy to spot. Joe Warfel found this Caddo agilis in the Estabrook Woods at the end of May. It was at the base of a tree trunk which is typical habitat for it, but you may also find them on the ground. The tiny ones, like the Caddo species, are very hard to spot until they move. On June 14, I found one of the larger species of Daddy Long-legs in the holly bushes in my yard. It had recently molted; its legs were still silvery and its body very pale so it stood out against the green of the leaves.
General characteristics: Daddy Long-legs, like spiders, have eight legs, but after that there is little similarity. Daddy Long-legs have only two eyes where spiders have eight. They make up for this with sensory organs on the legs especially the second pair which is usually much longer than the others. The head and thorax (aka the prosoma) is so broadly joined to the abdomen that it looks like the creature has an oval-shaped body with no “waist.” Unlike spiders, they don’t produce venom and they don’t make silk. They do have scent glands which produce acrid secretions to deter predators. They are also able to shed a leg if a predator has hold of it and continue life more or less normally. The detached leg will continue to twitch thus retaining the attention of the predator while the Daddy escapes.
Specific characteristics: The little Caddo has a body about one tenth of an inch long. Its legs are about 5 times as long and it stands tall. (Lots of other Daddy long-legs are sprawly and carry their bodies much closer to the ground.) C. agilis can also be recognized by the very broad mound where the eyes are placed. The eyes appear as if on the sides of the body rather than in the middle. The eyes are large in comparison to the body size. The creature has a characteristic way of moving in fits and starts. Now you see it and now you don’t.
References: Invertebrate Zoology, Robert D. Barnes: Spiders and Their Kin, Herbert W. Levi; Harvestmen; Biology of Opiliones, published by Harvard University Press; and special thanks to Joe Warfel, an expert nature photographer and source of knowledge about Opilionids and other arachnids.
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