Phalangium opilio
Harvestmen are generally found on their own and therefore have developed some innovative defensive behaviors to protect themselves from predators. When threatened, they participate in a defensive technique called bobbing, which vibrates their whole body and makes it harder for the predator to grab onto them. If this is unsuccessful and a predator gets ahold of a harvestmen’s leg, they can easily detach the appendage at the joint between their femur and trochanter. The detached leg can continue twitching for up to an hour to distract the predator and allow the Phalangium opilio to get away (Although, this trick is not without consequence, because harvestmen leg segments cannot regenerate). In addition to this, Phalangium opilio possess chemical defenses that are released from their scent glands on their prosoma. This liquid or gas compound encompasses the arachnid’s body and discourages predators from eating them.
Photo (right) from: https://www.semanticscholar.org/paper/Predator-interactions-within-a-trophic-level-%3A-L.-Merfield/5653452c5f1b6599c077b1f6e4fee90dc77e0c82 Phalangium opilio are more than just prey for insectivorous species, they also provide great pest control for gardens, crops, and residential landscapes. While harvestmen species alone cannot control pest populations, their broad and pest-filled diets help contribute to biological control and keep pest’s from overtaking local plant life. Considering their importance, avoiding the use of bread spectrum insecticides can help protect harvestmen populations. On a smaller scale, you can help Phalangium opilio and protect them from dehydration, by providing rocks, mulch, and logs in your garden to be used as shelter from the sun.
Photo (right) from: https://www.naturespot.org.uk/species/phalangium-opilio |
Phalangium opilio is one of many known species of harvestmen, which are arachnids in the order Opiliones. Harvestmen are referred to by many common names including shepherd’s spiders, harvest spiders, reapers, and here in the United States, daddy longlegs. Like spiders and mites, harvestmen have two body sections, eight legs, and no antennae. However, unlike spiders, the two body sections are broadly joined, and harvestmen do not possess web spinning organs. Phalangium opilio, have long, slender legs and a short, round body. Coloration is typically a mixture of grays and browns with a cream underbody.
Photo (left) from: http://www.sharmalabuw.org/development-and-evo-devo.html After mating, female Phalangium opilio utilize their long ovipositors to deposit ten to several hundred eggs under rocks, in cracks in the soil, or between the soil and the crowns or recumbent leaves of plants. The eggs can take three weeks to five months to hatch, depending on temperature. Immature Phalangium opilio undergo several molts and can take another two to three months to reach maturity, again depending on temperature. The length of the adult stage varies from one to two months to a year or more. In temperate climates like Ohio, harvestmen can overwinter as eggs, immatures or adults, allowing for two or more generations to occur per year. During their lifetime, harvestmen consume both dead and live soft-bodied prey. Unlike spiders, who inject venom into their prey, harvestmen hold their prey with their chelicerae and pedipalps to tear it apart for consumption. Phalangium opilio are not picky eaters, feasting on arthropods like aphids, psyllids, grasshoppers, beetle larvae, slugs, mites, caterpillars, lady beetle eggs, spiders, and even other harvestmen. Outside of food sources, these arachnids need to stay close to sources of water because they are very susceptible to dehydration. Furthermore, harvestmen tend to be more active at night and seek shelter from the sun during the day.
Photo (left) from: https://ohioline.osu.edu/factsheet/ent-68 |
References
Gardiner, Mary. “Ohio's Natural Enemies: Harvestmen (Also Known as Daddy Longlegs).” Ohioline, 14 Jan. 2016, ohioline.osu.edu/factsheet/ent-68.
Schmaedick, Mark. “Phalangium Opilio (Arachnida: Opiliones, Phalangiidae).” Cornell University College of Agriculture and Life Sciences, biocontrol.entomology.cornell.edu/predators/Phalangium.php.
Schmaedick, Mark. “Phalangium Opilio (Arachnida: Opiliones, Phalangiidae).” Cornell University College of Agriculture and Life Sciences, biocontrol.entomology.cornell.edu/predators/Phalangium.php.