Anoetus

 

HARMFUL | NOT HARMFUL | UNCERTAIN

mutualists; feed on microorganisms on provisioned pollen and developing bees and reduce fungal infestation in nest cells via fungicides, increasing survival rates of developing bees.

Name and classification

Anoetus Dujardin, 1842

Taxonomy
Superorder Acariformes » Order Sarcoptiformes » Suborder Oribatida » Infraorder Desmonomata » Hyporder Astigmata » Family Histiostomatidae » Genus Anoetus

Type species
Hypopus alicola Dujardin, 1849

Common synonyms
In old literature, the name Anoetus was used to group species now assigned to genera Histiostoma and Anoetus.

Diagnosis

Phoretic deutonymph: Solenidion ω1 of leg I positioned directly on tibia, associated with tibial solenidion phi (φ) (Fig. 6) and claws III and IV small (as compared to membranous ambulacra), thin, and linear (Fig. 8).

Other diagnostic characters

Phoretic deutonymph: Empodial claws I-IV simple (not bifurcated) (Figs. 7-8). Tarsi III and IV with a weak, flexible region in middle of segment (Fig. 8). Pretarsi III and IV with empodial claws (Fig. 8). Trochanters I-II without setae. Anterior prodorsum without a pair of brown pigmented areas (Fig. 1). Anterior edge of dorsal hysterosoma entire, smooth (not scalloped) (Fig. 1). Anterolateral region of hysterosoma without lens-like organs (Fig. 1). Hysterosomal setae c1, d1 and e1 filiform (not lanceolate) (Fig. 1). Attachment organ wider than long (Fig. 5). Coxal fields IV closed (Fig. 2). Setae of coxa I and III (1a and 3a) either all filiform (Fig. 4) or conoidal. Gnathosoma subquadrate to trapezoidal, generally wider than long (Fig. 3).

Female: Pretarsi with membranous ambulacrum short, not bilobed. Posterior genital "rings" not associated with the anus (Fig. 12). Coxal setae I, III, IV present (may be small) (Fig. 12). Palps very small and bulbous (Fig. 13). Dorsal sclerite very reduced or absent (Fig. 11).

Male: Paranal suckers absent. Aedeagus thin, usually short and often posteriorly directed. Without large spine-like setae at base of aedeagus. With only one pair of genital "rings." Mouthparts vestigial. Leg and body setation strongly reduced.

Similar genera

Phoretic deutonymphs of Anoetus are very similar to those of Histiostoma. In Anoetus, claws III - IV are very small (as compared to width of membranous ambulacra) and thin, linear; gnathosoma subquadrate. In Histiostoma claws III-IV are large (as compared to width of membranous ambulacra), claw III is claw-like, claw IV either claw-like or linear; gnathosoma subquadrate or elongated.

Distribution

Nearctic, Palaearctic (including N. Africa), Neotropical, and Australian regions.

Bee hosts

Halictid bees of the genera Lasioglossum, Lasioglossum (Dialictus), Halictus, Augochlora, and Megalopta. In old literature the honey bee, Apis mellifera, was cited as a host of Anoetus alicola; these records need to be verified.

Host association level

Permanent

associated exclusively with bees or their close relative, wasps; cannot live without these hosts

Temporary

some life stages are associated with bees, while others are not

Facultative or opportunistic

can complete entire life cycle without bees or their close relative, wasps

permanent

Host associations, feeding, and dispersal

  • All stages live in nests of halictid bees. Tritonymphs and adult females feed on microorganisms on provisioned food, while larvae and protonymphs feed on microorganisms on developing bee larvae, possibly providing sanitary services in the nest.
  • Phoretic deutonymphs disperse on adult bees, often forming large clusters on propodeum or first metasomal tergite T1 of female bees, which function as a rudimentary acarinarium (Figs. 14-17). This 'acarinarium' is especially pronounced in Lasioglossum.

Biology

Biological observations are available for Anoetus halictonida, associated with Halictus rubicundus, and an undescribed species of Anoetus associated with Lasioglossum lineatulum (Eickwort, 1979; Eickwort, 1994):

Phoretic deutonymphs attach to the host's wings. On female bees they also often attach in shingle-like rows to metasomal tergum I or II, while on males they may occur on the venter of the head, thorax, and sometimes the metasoma. Phoretic deutonymphs move from their phoretic host onto the provision mass in a new cell, and transform into tritonymphs that soon molt into adults.

The adult females stay on the provision mass and swell greatly. The males remain very small and crawl onto the dorsum of the female when the host larva is about half grown. It is possible that these males develop rapidly from the first unfertilized eggs laid by the females, perhaps skipping all nymphal instars, and then mate with females of the parental generation. The inseminated females then lay fertilized eggs, all of which develop into females.

Those female eggs are laid on the bee nest cell wall and bee larvae, and mite larvae and protonymphs feed on the surfaces of the bee larvae and pupae, apparently consuming microorganisms; they do not harm the bees upon which they feed. Mite protonymphs begin to appear when the bee larva pupates, when they crawl on the pupa, especially ventrally. Molting to phoretic deutonymphs begins about half way through the pupal stadium. Phoretic deutonymphs preferentially cluster on the pupa's dorsal propodeal surface and about the wing bases. They transfer to the adult bee when it emerges. Deutonymphs remain on their female hosts while the hosts hibernate, and they detach from host bees as new cells are constructed in the spring.

In addition, field observations and laboratory experiments on Anoetus associated with halictid bees of the genus Megalopta showed that mites reduce fungal infestation of the nest cells, thus decreasing bee mortality (Biani et al., 2009).