Harvest mite
The harvest mite, also known as chigger or red bug, is a small, six-legged arachnid that serves as a significant pest during its larval stage. Measuring about 1.5 millimeters, these tiny creatures are notable for their reddish color and the severe skin irritation they can cause through their feeding habits. As larvae, they attach to hosts such as birds and mammals, including humans, using their sharp mouthparts to pierce the skin and extract tissue fluids. This feeding can lead to intense itching and a condition known as dermatitis, which may require medical attention.
Harvest mites are primarily active between July and September, hatching from eggs and feeding on their hosts for up to three days before detaching. While they cause minimal issues as nymphs or adults, they are known to potentially carry diseases, such as Oriental scrub typhus, via their saliva. After feeding, they drop to the ground to transition into their next life stages. Despite their impact on skin health, harvest mites are not considered a threatened species and have natural predators, including various insects and reptiles. Understanding the biology and lifecycle of harvest mites can help in managing their presence and mitigating the discomfort they cause.
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Harvest mite
As a larva, the harvest mite is a common and serious pest of people and a wide range of animals. This tiny, six-legged, red animal is commonly called a red bug or a chigger. It feeds on blood and causes severe rashes and itching in the skin and may also carry diseases.
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Trombidiformes
Family: Trombiculidae
Genus: Neotrombicula
Species: Autumnalis
As a nymph and as an adult, the harvest mite lives in the soil. A nymph is the stage of development between being a newly hatched larva and an adult. The nymph and adult probably live inside and feed on the eggs of arthropods. Arthropods are invertebrates, or animals without backbones, which have jointed bodies and limbs and usually have hard, shell-like skeletons on the outsides of their bodies. Examples of arthropods are insects, crustaceans, and arachnids, such as spiders, scorpions, ticks, and mites.
Although the harvest mite causes little trouble when it is a nymph or adult, it is a parasite and pest as a larva. A parasite is any animal or plant which feeds and lives on another plant or animal, called a host. The hosts of the harvest mite larva are birds and a variety of mammals, including people. Harvest mite larvae are often found in rodents, small mammals like rabbits, and larger mammals like horses. The harvest mite is known around the world by its more common names of chigger or red bug. Some people may also call it a jigger or a chigoe.
Chiggers begin hatching from their eggs between July and September. Each chigger is around 1 1/2 millimeters long and has a small head and a round, hairy body with six hairy legs. The chigger has four mouthparts. Two of these are sensory organs called pedipalps which help sense food. The other two are called chelicerae and are sharp, needle-like jaws for piercing the skin of the chigger's victim. The chigger inserts its jaws and releases saliva to digest a canal into cells below the skin. It then sucks the tissue fluid and other cell contents. It may remain attached to its victim and feed for three days before it releases its tight grip on the skin.
A chigger may cause severe irritation in the skin of its victim. The skin becomes red with a rash and itches. This condition is called dermatitis and may need treatment by a doctor. A chigger often feeds on the ankles, around the upper parts of the legs, the wrists, armpits, and ears. In some parts of the world, a chigger may also carry certain diseases and transfer them to its victims when it feeds. One such disease is Oriental scrub typhus. This is caused by a microscopic organism called a rickettsia which is in the chigger's saliva and enters the blood of the victim.
After feeding, a chigger drops from the animal or person into the ground. It then molts, or sheds, its skin and becomes a nymph with eight legs. After another molting, it is an adult. It is not known how long this process takes or how long an adult harvest mite lives, although it may be up to a year. Other insects, ants, centipedes, and lizards are natural predators of the harvest mite. The harvest mite is not a threatened species.
Bibliography
“Biting Mites.” San Mateo County Mosquito and Vector Control District, 28 Feb. 2024, www.smcmvcd.org/biting-mites. Accessed 9 Apr. 2024.
Lederman, Nicole. “Neotrombicula Autumnalis: Information.” Animal Diversity Web, 2012, animaldiversity.org/accounts/Neotrombicula‗autumnalis. Accessed 9 Apr. 2024.