Imparipes

 

HARMFUL | NOT HARMFUL | UNCERTAIN

neutral or beneficial commensals; feed on fungi and waste from developing bee larvae

Name and classification

Imparipes Berlese, 1903

Taxonomy
Superorder Acariformes » Order Trombidiformes » Suborder Prostigmata » Infraorder Eleutherengona » Hyporder Heterostigmata » Family Scutacaridae » Genus Imparipes

Type species
Imparipes histricinus Berlese, 1903

Diagnosis

Female: Tergite C completely covers prodorsum, forming a characteristic ‘roof’ with striated margin (Fig. 1). Alveolar channel of setae c2 strongly sclerotized (Fig. 3). Setae c1 in central part of tergite C (not on its free striated margin) (Fig. 3). Pharyngeal pump (a muscular wall around pharynx that aids with ingestion) ph2 much larger than ph1 and ph3 (Fig. 5). Claw I not enlarged (Fig. 6). Legs IV with 5 segments (trochanter, femur, genu, tibia, tarsus) and ambulacrum (Fig. 7). Tibia IV with 3 setae (d, l’, v’) (Fig. 7). Tarsus IV abruptly becomes thin distal to point indicated by arrow on Fig. 7. Basal part of gnathosoma not elongated (Fig. 2).

Species identification

Species-rich genus, containing both bee-associated and non bee-associated mites. Except for the key to Palaearctic species (Khaustov, 2008), no keys are available. There are 15 species associated with bees, which should be identified using original descriptions.

Distribution

Palaearctic, Nearctic, Neotropical, and Afrotropical regions.

Bee hosts

Halictidae (Halictus, Lasioglossum, Lasioglossum (Dialictus), Augochlorella, and Nomia), Colletidae (Hylaeus), Andrenidae (Andrena), Megachilidae (Osmia, Megachile), and Apidae (Apis mellifera, Dasypoda, and Bombus)

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 bees, where their development occurs in eclosed cells. Mites feed on fungi and waste from developing bee larvae. Adult male does not feed.
  • Mite females disperse on adult bees. Some species (e.g. Imparipes haeseleri) transfer spores of particular fungi into their sporothecae. The fungus then is used as a food source by the mites developing in the bee nest.

Biology

The following is a summary of the biology of Imparipes apicola as described in Cross and Bohart, 1992.

Female mites are phoretic on bee hosts, dropping off into new cells as they are constructed and provisioned. In the nest, this species is a fungivorous commensal, completing its life cycle in cells containing diseased or healthy bees. In cells containing healthy bees, foundress mites normally initiate ovogenesis only at the time of larval bee defecation. Fungus of the genus Ascosphaera is of fundamental importance to Imparipes apicola. This fungus is ingested by the developing bee larva and germinates in the gut, where it develops without harming the bee, and is passed in the feces, stringing the fecal pellets together in characteristic fashion. Its presence probably cues the initiation of ovogenesis in mite females, and it is also a primary source of mite food. Female mites overwinter in the bee cell and attach to emerging bees the following summer.

The mite egg hatches into the larva (the only immature stage). After molting, larvae develop ino either feeding females or non-feeding males, although most of the feeding occurs during the larval stage. In cells with healthy bees, mite larvae have usually been found on the fecal mass, where they appeared to be feeding, but in certain cells showing disease, especially those containing soupy pollen, they have been found more commonly in the upper portions of the cell. In healthy cells, they often appeared to feed from the sparse mycelia growing from the feces and along the cell walls, and especially from the thick strands characteristic of Ascosphaera.