Sennertia

 

HARMFUL | NOT HARMFUL | UNCERTAIN

some species are kleptoparasitic or predatory, feeding on pollen or causing detah of eggs or larvae; some species suspected to be neutral or mutualistic where bees have acarinaria to hold mites; details of biology unknown

Name and classification

Sennertia Oudemans, 1905

Taxonomy
Superorder Acariformes » Order Sarcoptiformes » Suborder Oribatida » Infraorder Desmonomata » Hyporder Astigmata » Family Chaetodactylidae » Genus Sennertia

Type species
Pediculus cerambycinus Scopoli, 1763

Diagnosis

Phoretic deutonymph: Gnathosomal solenidion present, setae on free palpi absent, and free palpi absent (Fig. 16). Only hysterosomal shield present on idiosoma; propodosomal shield absent (Fig. 7). Cupules im situated at level of trochanters of legs III (Fig. 17).

Adults: Cupules im dorsal (correlates with character in deutonymph) (Fig. 18).

Male: Progenital sclerites lateral to genital capsule (Fig. 19). Progenital sclerites distinctly separated and not touching each other (Fig. 20). Dorsal supporting sclerite not extending posterior to base of aedeagus (Fig. 20).

Distribution

Worldwide, except for Antarctica. Most mites associated with Xylocopa form clear morphology-based New and Old World lineages. The Sennertia zhelochovtsevi species group is an exception. It is distributed in the Old World but is related to the New World lineage. In contrast, species of Sennertia associated with Ceratina do not form distinct, geographically defined lineages.

Bee hosts

Most species ocur on small carpenter bees (Ceratina) and large carpenter bees (Xylocopa) of the family Apidae. A few species (Sennertia vaga-group) are associated with Centris (Paracentris) in the Neotropics.

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

  • For the majority of species, feeding stages live in nests of carpenter bees (Xylocopa, Ceratina, and rarely Centris), where they consume provisioned pollen. Mites of the Sennertia vaga-group can probably complete their life cycle both in the nest and on adult bees. Mutualistic relationships are expected for associations where adult female bees develop acarinaria (see below). For other associations, the mite presence is probably somewhat harmful or neutral.
  • Phoretic deutonymphs disperse on adult bees from one nest to another, either externally (Figs. 9-13) or internally in the genital acarinarium of female bees. Some neotropical Ceratina develop metasomal acarinaria to transfer mites (Fig. 14). The Sennertia vaga-group is an exception; its feeding stages can disperse on adult bees.

Biology

The interactions of Sennertia with their hosts in nests remain largely unknown. There are conflicting accounts suggesting either negative or neutral effect of the mite presence. In the former case, the damage to developing bees was marginal and always substantially less than that of Chaetodactylus.

Feeding stages of the Sennertia vaga-group are unusual because they can disperse on adult bees of the genera Centris (Paracentris) and Xylocopa (Fig. 8). Reproduction and feeding can also occur during dispersal. Species of the Sennertia vaga group probably do not form phoretic deutonymphs and disperse exclusively as feeding stages. Observations on these mites inside nests are lacking.

Phoretic deutonymphs (non-feeding stages, Figs. 1-7) disperse on adult bees from one nest to another (Figs. 9-13). Ceratina bees associated with Sennertia (S. sayutara and S. devincta) have acarinaria, indirectly suggesting mutualistic relationship between the mites and the bees (Fig. 14). Some other bees have rudimentary acarinaria that their mites take advantage of for phoresy. Sennertia koptorthosomae and S. hipposideros, which are associated with Asian large carpenter bees (Xylocopa), have special pouches filled with fungal spores (sporothecae) on the hysterosoma (Klimov and OConnor, 2008) (Fig. 15), suggesting that they may transfer fungi from one bee nest to another. It is unknown whether these fungi can cause harm to the bee host.

Sennertia cerambycina (Fig. 2) is normally associated with Xylocopa, feeding on the provisioned pollen in the bee nest. Rarely, dead bee eggs and larvae can be found in the infested cells. However, it is unclear if the mite directly or indirectly causes death of eggs or larvae (Vicidomini, 1996). Adult bees of Xylocopa violacea extensively infested with S. cerambycina show slow flight, lack of precision in flying trajectories, difficult and imprecise landing, heavy take-off, and reduced feeding rates (Vicidomini, 1999).

Duchemin (1886) reported the death of 30 honey bee (Apis mellifera) hives in France attributable to a mite identified originally as Sennertia cerambycina. The mite infests honey bees visiting sunflowers, eventually causing death of colonies. Similar cases (e.g., death of honey bee colonies with the introduction of sunflowers) were reported in Russia at the end of 19th to the beginning of the 20th century (reviewed in Grobov, 1978). Experimental data suggesting that the mite is responsible for the death of bees are, however, absent. Furthermore, misidentification is possible here and it may be that another mite species, not belonging to the genus Sennertia, was involved in these cases.