kleptoparasitic or neutral to beneficial, depending on life stage; females and deutonymphs feed on provisioned pollen, while other stages are predators of small arthropods

Name and classification

Parasitellus Willmann, 1939

Superorder Parasitiformes » Order Mesostigmata » Suborder Monogynaspida » Hyporder Parasitiae » Family Parasitidae » Genus Parasitellus

Type species
Eugamasus (?) ferox Tragardh, 1910 (= Acarus fucorum De Geer, 1778)

Common synonyms
In old literature has been treated as part of Parasitus Latreille, 1795.

Similar genera

Parasitellus can be distinguished from all other genera of Parasitidae by the opisthogastric region having more than 40 pairs of setae (Fig. 2). This region has fewer than 30 pairs of setae in other genera of Parasitidae.


Common in the Holarctic region (North America, Europe, Northern Asia, and China). Also reported in the Neotropical region (Argentina and Mexico).

Bee hosts

All species of the genus Parasitellus are obligatory associates of bumble bees (Bombus). Several occasional records are from honey bee (Apis) hives and burrows of small mammals (which are preferential sites for bumble bee nests).

Host association level


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


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


Host associations, feeding, and dispersal

  • All stages live in nests of bumble bees (Bombus spp.), where females and deutonymphs feed on pollen and other stages feed on small arthropods.
  • Mite deutonymphs disperse and overwinter on adult queen bees. Phoresy on workers and males of bumble bees or cuckoo bumble bees is also documented.


All species of Parasitellus inhabit nests of bumble bees (Bombus). Mite deutonymphs are commonly phoretic on adult bumble bees or cuckoo bumble bees. Phoretic mites prefer queens to other castes (workers and males), since bumble bee colonies are annual and only young queens overwinter. Mites dispersing on workers and males may try to switch to queens later, either during copulation or on flowers, where bumble bees forage (Huck et al., 1998; Schwarz and Huck, 1997).

Species of Parasitellus are not specific to a particular bumble bee species, with different mite species often co-occurring in a single Bombus nest or co-dispersing on a single bee individual.

The nature of the association between Parasitellus and its bumble bee hosts is a balance between being harmful and beneficial. In Parasitellus fucorum, males, larvae, protonymphs, and possibly deutonymphs, have been found to be predatory or oophagous (egg-feeding) on microarthropods in bumble bee nests and thus, beneficial to the bees, while adult females and deutonymphs preferentially feed on the provisioned pollen and are harmful to the host (Koulianos and Schwarz, 1999).

Mites feed on the upper layer of pollen grains (nectar coating and pollenkitt), without damaging them otherwise. Pollen grains processed in this way lost their normal bright yellow or blue color and became pale and more translucent (Koulianos and Schwarz, 1999).