Identification

Which life stage should I use for identification?

The life stages that are useful for identifying mites are adults and specialized dispersal stages called phoreticphoretic:
Pertaining to phoresy; using another organism (i.e., a host) for dispersal to new habitats. Phoresy can be distinguished from parasitism because feeding typically does not occur during phoresy.
deutonymphsdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
. If you sample from mites on an adult bee, almost every specimen will be either a phoreticphoretic:
Pertaining to phoresy; using another organism (i.e., a host) for dispersal to new habitats. Phoresy can be distinguished from parasitism because feeding typically does not occur during phoresy.
deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
or a female, both of which are useful for identification. In some Prostigmata that are permanentpermanent:
associated exclusively with bees or their close relative, wasps; cannot live without these hosts
parasites, adult males and juveniles may also be found. If you sample from an adult bee's internal tracheae or air sacs, adult mites are the most important stage for identification. And if you sample from a bee nest, the best strategy is to obtain adults by collecting as many mites as possible. While adults, especially females, are the largest stage, the immature stages are usually more numerous in nests, and it is not always possible for non-acarologists to confidently distinguish adults (especially males) under a dissecting microscope. A large sample should ensure that adults are included.

How do I recognize each stage?

Mites may pass through up to six instars: prelarva, larva, protonymphprotonymph:
Ontogenetic stage between larva and deutonymph. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, tritonymphtritonymph:
Ontogenetic stage between the deutonymph and adult. Sometimes this stage is absent and deutonymph transforms directly to the adult stage. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, and adult. These developmental stages may look different or may be omitted depending on the mite group. All mites have an adult stage; the female is the dispersal stage in some Mesostigmata and Prostigmata. DeutonymphsDeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
may also be the dispersal stage in Mesostigmata and Astigmata. The deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
is unspecialized or slightly specialized in Mesostigmata.

In Astigmata, the larva, protonymphprotonymph:
Ontogenetic stage between larva and deutonymph. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, tritonymphtritonymph:
Ontogenetic stage between the deutonymph and adult. Sometimes this stage is absent and deutonymph transforms directly to the adult stage. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, and adult are usually feeding ontogenetic stages, though exceptions occur, while the deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
serves for dispersal or survival in severe conditions, lacks mouthparts, and cannot feed (though non-oral feeding is possible in several taxa). DeutonymphsDeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
have many morphological specializations for phoresyphoresy:
Attaching to or boarding another organism (i.e., a host) for dispersal to new habitats. Can be distinguished from parasitism because feeding typically does not occur.
, and they are strikingly different from other life stages.

In the fact sheets we describe and illustrate adults and give specific information on what the dispersal stage is in the life cycle for each mite lineage. If this stage is not the adult female, then a dispersal stage is also described and illustrated. Consult the fact sheets to determine which life stages are relevant for identifying each genus. Below we provide general information about mite developmental stages.

 

Life stages of Chaetodactylus krombeini (Astigmata); male not shown; individual LT-SEM photos (excluding phoretic deutonymph photo) by Ron Ochoa and Gary Bauchan, USDA-ARS

 

Life stages of Varroa destructor (Mesostigmata); four individual photos by Gilles San Martin/Flickr; male deutonymph and larva photos by MrJEberhardt/Youtube

Prelarva

This is the first ontogenetic stage in mite development. In bee-associated mites, the prelarva is inactive, non-feeding, and sac-like (no legs or mouthparts). It develops inside the egg chorion where it consumes yolk and it molts into a larva. The prelarva is absent in Mesostigmata.

Larva

This is an active, feeding instar invariably present in mite life cycles. After eclosion, larvae shed both prelarval skin and chorion. In most bee-associated mites, this is the first active stage. It is usually a weak, miniature stage, but in some groups, larvae are aggressive parasites (Parasitengona) or predators (family Cheyletidae). In contrast, in most Mesostigmata (e.g., Varroa), the larval stage is short-lived and non-feeding, sometimes remaining within the egg chorion.

IDENTIFICATION

• Mite larvae have three pairs of legs.
• Larvae lack functional external genital structures related to reproduction and oviposition. In taxa with genital papillae:genital papilla:
  Paired, eversible, finger- or bell-shaped structures situated under the genital valves (in the progenital chamber) of many Acariformes, which serve for osmoregulation. In feeding stages of Histiostomatidae (but not phoretic deutonymphs) these are modified to cuticular rings situated externally on the ventral body.
  : (Oribatida and Astigmata), larvae often have Claparède organs.
• Males of Locustacarus buchneri (Podapolipidae) are an exception: they are born sexually mature and have external genitals developed; in this species all larvae are females that can copulate with males but cannot lay eggs.

Nymphal stages

There are three possible nymphal stages separated by molts: protonymphprotonymph:
Ontogenetic stage between larva and deutonymph. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, and tritonymphtritonymph:
Ontogenetic stage between the deutonymph and adult. Sometimes this stage is absent and deutonymph transforms directly to the adult stage. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
. One of the stages may be either permanently or optionally suppressed, resulting in only two nymphal stages. Rarely, there is only one nymphal stage. Nymphal stages are suppressed in some Trombidiformes (Podapolipidae, Tarsonemidae, and Pyemotidae). A nymphal stage can be facultativefacultative:
can complete entire life cycle without bees or their close relative, wasps
, depending on particular circumstances.

In bee-associated Astigmata, deutonymphsdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
are heteromorphic with respect to other stages and may also be polymorphic. There are two types of deutonymphsdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
for these taxa: (1) phoreticphoretic:
Pertaining to phoresy; using another organism (i.e., a host) for dispersal to new habitats. Phoresy can be distinguished from parasitism because feeding typically does not occur during phoresy.
deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, an active and typically non-feeding stage serving for attachment and dispersal on insect hosts; and (2) non-phoretic (or immobile) deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
, a highly regressive, cyst-like stage serving for survival in adverse conditions. The phoreticphoretic:
Pertaining to phoresy; using another organism (i.e., a host) for dispersal to new habitats. Phoresy can be distinguished from parasitism because feeding typically does not occur during phoresy.
deutonymphdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
is a facultativefacultative:
can complete entire life cycle without bees or their close relative, wasps
stage; it only appears when there is a need for dispersal. Many bees only use nests for a single generation, so mites feeding on pollen inside those nests are doomed unless they can disperse to other nests that have adult bees. The life cycle of mites is therefore synchronized with that of their bee hosts, and the dispersal stage appears when adult bees are about to emerge and leave the nest, thus dispersing mites to new nests. In bee-associated mites, non-phoretic deutonymphsdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
are known only in Chaetodactylus and certain species of Glycyphagus and Acarus. In Chaetodactylus, which is associated with solitary bees constructing nests only for a single generation/season, the deutonymphsdeutonymph:
Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
remain in the nest cavity waiting for the nest to be re-used by other bees rather than dispersing.

IDENTIFICATION

 

Cultured life stages (feeding stages only) of Chaetodactylus krombeini (Astigmata). Pollen grains visible.

• Nymphs have four pairs of legs and lack functional external organs related to reproduction and oviposition. In some groups, the nymphal stages can only be distinguished by experts.
• In Oribatida, different nymphal stages can be relatively easily identified by the number of genital papillae:genital papilla:
  Paired, eversible, finger- or bell-shaped structures situated under the genital valves (in the progenital chamber) of many Acariformes, which serve for osmoregulation. In feeding stages of Histiostomatidae (but not phoretic deutonymphs) these are modified to cuticular rings situated externally on the ventral body.
  :: the protonymphprotonymph:
  Ontogenetic stage between larva and deutonymph. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  has 1 pair, deutonymphdeutonymph:
  Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  2 pairs, and tritonymphtritonymph:
  Ontogenetic stage between the deutonymph and adult. Sometimes this stage is absent and deutonymph transforms directly to the adult stage. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  and adult 3 pairs.
• In Astigmata the protonymphprotonymph:
  Ontogenetic stage between larva and deutonymph. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  has 1 pair of genital papillaegenital papilla:
  Paired, eversible, finger- or bell-shaped structures situated under the genital valves (in the progenital chamber) of many Acariformes, which serve for osmoregulation. In feeding stages of Histiostomatidae (but not phoretic deutonymphs) these are modified to cuticular rings situated externally on the ventral body.
  , deutonymphdeutonymph:
  Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  2 pairs, and tritonymphtritonymph:
  Ontogenetic stage between the deutonymph and adult. Sometimes this stage is absent and deutonymph transforms directly to the adult stage. See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  and adult 2 pairs. The deutonymphdeutonymph:
  Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  is phoreticphoretic:
  Pertaining to phoresy; using another organism (i.e., a host) for dispersal to new habitats. Phoresy can be distinguished from parasitism because feeding typically does not occur during phoresy.
   and is very different from any other stage. It is easily identified by the presence of the attachment organattachment organ:
  Complex unpaired structure in phoretic deutonymphs of Astigmata situated on the posteroventral end of the body that serves for attachment to the host during phoresy. In deutonymphs phoretic on insects, attachment organ consists of a vestigial anal opening and two types of attachment elements: true suckers that create negative pressure and conoids that create adhesive forces. Not to be confused with pedicel.
   and the lack of functional mouthparts. A few taxa in the families Chaetodactylidae, Glycyphagidae, and Acaridae have non-phoretic, immobile deutonymphsdeutonymph:
  Ontogenetic stage between protonymph and tritonymph (or adult, if tritonymph is absent). See <a href="index.cfm?pageID=1720">Life stages page</a> for more details.
  . This stage is a featureless sack with greatly reduced legs, attachment organattachment organ:
  Complex unpaired structure in phoretic deutonymphs of Astigmata situated on the posteroventral end of the body that serves for attachment to the host during phoresy. In deutonymphs phoretic on insects, attachment organ consists of a vestigial anal opening and two types of attachment elements: true suckers that create negative pressure and conoids that create adhesive forces. Not to be confused with pedicel.
  , and mouthparts, and it usually stays under the protonymphal skin.

Adult

The adult is a sexually mature stage that cannot molt anymore, though rare instances of adult molts are known.

IDENTIFICATION

• Adults have four pairs of legs and functional external organs related to reproduction. The exception is Locustacarus buchneri (Podapolipidae): this species' adult females have 1 pair of legs and the larviform males have 3 pairs (like the larva of many other mites). Larviform males of this species can copulate with larviform females, though only adult females lay eggs.
• The adult female has an oviporeovipore:
  Opening of female which serves as an outlet for oviposition. In Astigmata and non-astigmatan Oribatida, situated between genital valves. In Astigmata, not to be confused with the copulatory opening (which serves for sperm intake).
  , and the male has either an aedeagusaedeagus:
  An external organ of a male arthropod that is specialized to deliver sperm during copulation.
  , a gonopodegonopode:
  An appendage specialized to transfer sperm, such as the modified male chelicera in Mesostigmata.
  , or a spermatopositorspermatopositor:
  A small male organ for depositing spermatophores.
  . A sperm access system not connected with the oviporeovipore:
  Opening of female which serves as an outlet for oviposition. In Astigmata and non-astigmatan Oribatida, situated between genital valves. In Astigmata, not to be confused with the copulatory opening (which serves for sperm intake).
  is present in Astigmata, Prostigmata (Tetranychidae), and some Parasitiformes (Dermanyssina and Heterozerconina). In these cases, the oviporeovipore:
  Opening of female which serves as an outlet for oviposition. In Astigmata and non-astigmatan Oribatida, situated between genital valves. In Astigmata, not to be confused with the copulatory opening (which serves for sperm intake).
   and copulatory opening are separate and disconnected.