Stigmaeidae is a family of

prostigmata Prostigmata is a suborder of mites belonging to the order Trombidiformes, which contains the "sucking" members of the "true mites" (Acariformes). Many species are notorious pests on plants. Well-known examples of prostigmatan plant parasites ...

mite Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as eac ...

s in the order

Trombidiformes Trombidiformes is a large, diverse order of mites. Taxonomy In 1998, Trombidiformes was divided into the Sphaerolichida and the Prostigmata. The group has few synapomorphies by which it can be defined, unlike the other major group of acariform ...

. At over 600 species, it is the largest family in superfamily

Raphignathoidea Raphignathoidea is a superfamily (taxonomy), superfamily of the Acari (mite) order (biology), order Trombidiformes, comprising 1087 species in 62 genera and 12 Family (biology), families. Morphology Adult Raphignathoidea are generally oval or ...

. It has a worldwide distribution.

Description

As mites, Stigmaeidae have unsegmented bodies with eight legs (six in larvae). They can be recognised by: prodorsum without transversal groove, sacs or tubes; suranal and aggenital shields separate; cheliceral bases usually separate (rarely fused or conjunct);

palps Pedipalps (commonly shortened to palps or palpi) are the secondary pair of forward appendages among chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicera ...

stout with tibial claws at least 1/3 length of tarsus; peritreme absent. Males differ from females in being somewhat tapered posteriorly.

Life cycle

The stigmaeid life cycle has the five stages of egg, larva, protonymph, deutonymph and adult. The larva and two nymph stages are also each followed by a quiescent period. The whole life cycle takes no more than four weeks. Males usually reach adulthood slightly faster than females, allowing them to mate with females as soon as the latter have reached adulthood. Offspring exhibit a female-biased

sex ratio A sex ratio is the ratio of males to females in a population. As explained by Fisher's principle, for evolutionary reasons this is typically about 1:1 in species which reproduce sexually. However, many species deviate from an even sex ratio, ei ...

(often in the 60-70% range), except for offspring of unmated females which are all male. Most Stigmaeidae are active year-round, but some species are known to go into

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press It ...

for the winter. Overwintering locations include litter at the base of trees and under bark scales on apple.

Habitat

Over a third of Stigmaeidae species are free-living

predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

that occur on the leaves and branches of plants (e.g. many ''Agistemus'' and ''Zetzellia''). There are also stigmaeids (e.g. many ''Eustigmaeus, Ledermulleriopsis'' and ''Stigmaeus'') that live in soil and leaf litter and are believed to feed on

moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

. A few species live on the surface of freshwater, in animal nests or attached to

sandflies Sandfly or sand fly is a colloquial name for any species or genus of flying, biting, blood-sucking dipteran (fly) encountered in sandy areas. In the United States, ''sandfly'' may refer to certain horse flies that are also known as "greenhead ...

. Some species can survive, feed and even develop while immersed in water, but cannot reproduce.

Diet

Predatory Stigmaeidae have generalist diets, consuming other mites (e.g.

spider mite Spider mites are members of the family Tetranychidae, which includes about 1,200 species. They are part of the subclass Acari (mites). Spider mites generally live on the undersides of leaves of plants, where they may spin protective silk webs, a ...

s, false spider mites, gall and rust mites and broad mites) as well as small insects (

Hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising more than 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from ...

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

) and plant

pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

. They usually prefer to feed on immature stages such as eggs. They feed by piercing prey with their chelicerae and sucking out the fluids. Moss-feeders, such as those in genus ''Eustigmaeus'' (formerly ''Ledermuelleria''), feed on moss leaves. They suck out cell contents while leaving the

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

s intact. They can feed and survive on many moss species, though only a few species allow mite reproduction. Stigmaeidae that attach to sandflies are presumed to be parasitic, leaving behind scars on the abdomens of their hosts.

Biological control

Due to their predatory activity, some stigmaeids (e.g ''Agistemus exsertus'' and ''Zetzellia mali'') have been studied for use as

biological control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or o ...

agents of pest mites. Modelling indicates that stigmaeids are more effective control agents than phytoseiids at low prey densities (but less effective at high prey densities), and a combination of stigmaeids and phytoseiids is more effective than either predator alone.

Genera

* '' Agistemus'' * '' Cheylostigmaeus'' * '' Eryngiopus'' * '' Eustigmaeus'' * '' Ledermuelleria'' * '' Ledermuelleriopsis'' * '' Mediolata'' * '' Mullederia'' * '' Primagistemus'' * '' Pseudostigmaeus'' * '' Stigmaeus'' * '' Storchia'' * '' Summersiella'' * '' Zetzellia''