40 Facts About Harvestmen or Daddy Longlegs That May Surprise You
Harvestmen are interesting arachnids. They are known for their long and spindly legs that make them look as though they're walking on stilts. Some people confuse them with spiders, which are also arachnids, but the two creatures are actually quite different animals. Despite rumours to the contrary, harvestmen are not dangerous to humans. They are intriguing creatures with some unusual features.
Harvestmen belong to the phylum Arthropoda, the class Arachnida, and the order Opiliones. They are also known as daddy longlegs or as granddaddy longlegs. Somewhat confusingly, cellar spiders and crane flies may also be referred to as daddy longlegs.
Spiders belong to the same phylum and class as harvestmen, but they belong to the order Araneae instead of the order Opiliones. Insects also belong to the phylum Arthropoda, but they don't belong to the class Arachnida and therefore aren't known as arachnids. The table below summarizes the relationship between harvestmen, spiders, and insects.
Arachnid and Insect Classification
The order name Opiliones comes from the Latin word opilio, which means shepherd. Harvestmen reminded earlier people of European shepherds who walked on stilts to get a good view of their flock. The animals are sometimes referred to as shepherd spiders, though as explained above they aren't spiders.
Differences Between Harvestmen and Spiders
1. The body of a spider is composed of two sections that often look different from one another. The cephalothorax or prosoma is joined to the abdomen or opisthosoma by a narrow stalk, though the stalk may not be visible when a spider is seen.
2. The harvestman also has a cephalothorax and an abdomen. The union between them is not obvious, however, and they look the same. The body appears to consist of just one section.
3. A spider has three or four pairs of eyes, which are generally positioned at the front edge of the cephalothorax. A harvestman has only one pair of eyes that are located on the top of the cephalothorax.
4. Most harvestmen have very long and spindly legs, but this isn't a foolproof way to identify them. Some have shorter and thicker legs. In addition, some spiders have long legs, though they aren't as long or as thin as those of a typical harvestman.
5. An urban legend says that harvestmen are the most venomous animals (or spiders) in the world. The reality is completely different. Unlike spiders, the animals don't have venom glands. In addition, the mouth and jaws, or chelicerae, are too small to do us much harm.
6. Harvestmen don't have silk glands and don't create a web. They do have glands that make a smelly secretion, though.
7. The body of a typical harvestman is very small in comparison to the legs. The body is often no more than half an inch in length and is usually smaller.
The bunny harvestman of Ecuador has attracted people's attention due to its "rabbit ears". The animal's body reminds people of a dog's head as well as a rabbit. Two yellow spots on the body look like eyes, though they aren't the arachnid's actual eyes. The animal's appearance may be designed to scare predators.
Distribution and Habitat of the Opiliones
8. Around 6,500 species of harvestmen are known. Some scientists believe that there are likely many more in existence. The animals are found on every continent except Antarctica.
9. The greatest variety of daddy longlegs is found in tropical areas. Though most of the animals have dull colours, some have green, yellow, and/or red markings, especially in the tropics.
10. The animals are often found in humid places, such as in leaf litter, crevices, and caves and under rocks and tree bark.
11. According to the University of Kentucky, harvestmen are sometimes seen in basements of houses. They may also be found in crawl spaces and in sheds and barns.
12. The name "harvestman" is derived from the fact that the animals are most often seen in late summer and early fall during the harvest season. They are visible during this season because it's generally the time when they mate.
The order Opiliones contains five suborders. Harvestmen are not widely studied. It's possible that some of the observed behaviours occur only in members of certain suborders.
Daily Life of a Harvestman
13. Harvestmen are often nocturnal, but some are partially or completely diurnal (active during the day). They dehydrate easily, so they often hunt briefly during the day and then go into hiding for a while.
14. The animals are omnivorous. They eat insects, spiders, mites, an occasional snail, and plant material. They are predators and possibly scavengers as well.
15. The pedipalps are short appendages that pick up food, manipulate it, and pass it to the mouth. They are located in front of the jaws, or chelicerae.
16. Researchers have discovered that in at least some harvestmen the tips of the pedipalps (or "feelers") have hairs that secrete a type of glue. This helps them to grab food.
17. The eyes of a daddy longlegs can detect the intensity of light, but the animals can't see images. They need the help of other senses to find their prey.
18. The animals have four pairs of legs, like a spider. The tips of the legs have multiple joints. They are covered with fine hairs and have a hook at the end.
19. The second pair of legs have sense organs and are used for probing the environment. They can detect vibrations and possibly certain chemicals. While many sources classify the second pair of legs as sensory appendages, a few say that the first pair of legs are more important for sensing the environment, at least in some suborders.
20. Harvestmen have been observed drawing their legs through their jaws to clean them. This behaviour can be seen in the bunny harvestman video above and in the first image in the photo sequence above.
A harvestman is sometimes covered with what appear to be red, orange, or yellow dots. These are actually mites that are parasitizing the animal. Mites are another type of arachnid.
21. Predators of harvestmen include spiders, scorpions (which like mites are arachnids), amphibians, lizards, and birds.
22. Daddy longlegs have pores that release a secretion with a bad smell. The secretion probably makes the animals both smell and taste bad to predators. One pore is located at the base of each front leg.
23. A harvestman sometimes releases a leg from its body in order to distract a would-be predator. The behaviour is known as autotomy. Unfortunately, the missing leg can't be regenerated, but the animal can often compensate for its deformity.
24. The detached leg twitches for a while, which probably serves to further distract the predator. The upper part of the leg contains a region that acts like a pacemaker, stimulating the rest of the leg to move.
25. A common defence mechanism in at least some daddy longlegs is to freeze when a predator is detected and to stay motionless until the danger has passed. Since the arachnid is frequently brown or a dull colour, this disguise often helps it to blend in with its environment.
26. Another defence mechanism shown by some species is known as bobbing. The animals vibrates rapidly, which appears to distract the predator.
27. Harvestmen sometimes gather in large groups, which look like hairy clumps due to the closeness of the many sets of long and thin legs. The animals interlock their legs as they cluster.
28. The clumps may form to provide warmth and a suitable humidity for the arachnids.
29. They may enhance the effect of the odoriferous substance released by the individual animals in order to repel predators.
30. The cluster as a whole sometimes jiggles or moves from one place to another, which may confuse a predator.
Mating Behaviour of Harvestmen
31. According to Kasey Fowler-Finn, a scientist who studies harvestmen reproduction, when a male and female find one another (by an unknown method), the male wraps his pedipalps around a female's sensory leg.
32. The male and female remain attached for seconds to several hours. There is some movement during the attachment period, though researchers don't know exactly what is happening. In at least one species, the male shakes the female's leg while attached. This may encourage her to mate again.
33. In some species, the male gives a female a "nuptial gift". The gift is a secretion from his mouth, which the female eats. This presumably stimulates mating.
34. Males have an intromittent organ, which extends from the male's body and enters the female's, delivering sperm. Fertilization is therefore internal.
35. Harvestmen are said to have direct fertilization because the sperm is transferred directly from the male's body into the female's. Spiders have indirect fertilization. The male spider first deposits sperm on a specially-woven sperm web. When a suitable female approaches, he picks the sperm up with a pedipalp and places it in an opening in the female's body known as the epigyne.
The video below shows two male harvestmen competing for the right to mate with a female. In some species, as in the one in the video (Leiobunum rotundum), the males are smaller than the females.
36. The female harvestman lays her fertilized eggs in soil, under tree bark, under leaves, or in another protected environment. She deposits them with a structure called an ovipositor.
37. The female may leave the eggs on their own, but in some species the female, the male, or both genders guard the eggs.
38. An egg hatches into a small version of the adult called a nymph.
39. A harvestman usually goes through six instars (nymphal stages) before adulthood is reached. The developing animal molts between each instar.
40. Like spiders, a harvestman has incomplete metamorphosis. The developmental stages look quite similar to the adult but differ in size.
A few species of harvestmen are parthenogenic. This means that the female can produce offspring without obtaining sperm from a male.
Exploring the Behaviour of Daddy Longlegs
Harvestmen have some curious characteristics and are worth observing. The reproductive behaviour of the animals is especially intriguing and has some puzzling aspects that need to be explained.
Some species of daddy longlegs that haven't yet been discovered may have even more intriguing behaviour for us to appreciate. Hopefully, researchers will learn more about the features of the world's daddy longlegs in the near future.
© 2018 Linda Crampton