Bee mites: Family Pyemotidae: Pyemotes beckeri, Pyemotes anobii; Apis, Hoplitis, Megachilidae, Apidae, host associations

Physogastric female of mite Pyemotes (Pyemotidae) ex Hoplitis (Hymenoptera: Megachilidae)

Fig. 1. Physogastric female of the mite Pyemotes sp. ex Hoplitis sp.(Hymenoptera: Megachilidae) from Colorado. Click here to enlarge

Bee Mites : Acari : Acariformes : Trombidiformes

Family Pyemotidae Berlese, 1897

This family includes three genera according to Lindquist (1986) and two genera with 25 species according to Kethley (1982). Adult females of Pyemotidae are parasites of all developmental stages of holometabolous insects, especially subcortical beetles and stored product insects. When the female sucks the haemolymph of the host her posterior opisthosoma becomes greatly swollen because of developing eggs (physogastric female). Eggs hatch within the female, and adults are the only developmental stage in the family. Adult males emerge first, pierce the swollen opisthosoma with their mouthparts and remain near the opening. Males copulate with females as the latter emerge from the mother's body. The copulation triggers searching behavior in females, which immediately leave to attack a suitable host.
One genus, Pyemotes Amerling, has been recorded parazitising bee larvae and pupae.

Genus Pyemotes Amerling, 1862

Pyemotes Amerling, 1862: 54 (Type species Piemotes Eccoptogasteri pruni Amerling, 1862 nom. nud. =? Pyemotes scolyti Oudemans, 1936 by original designation) (after Krczal, 1957, his synonymy)

The genus Pyemotes includes polixenous or monoxenous insect parasites exhibiting a wide variety of morphological polymorphisms. Some species of Pyemotes are natural enemies of forest insects or stored product insects. The genus is divided into two groups, scolyti and ventricosus (Cross et al., 1981).
Species of the scolyti group are phoretic on bark beetles (Scolytidae). At least one female morph is a phoretomorph. Phoretomorphic females are shorter than "normal" females and much broader, with thickened legs and enlarged claws. There are also two morphs in the male of Pyetomotes dimorphus Cross et Moser, 1975: "normal" and heteromorphic. The latter morph is distinctly larger, with many greatly enlarged setae, and sometimes setae are duplicated. The mites feed only on bark beetle brood or on immatures of other beetles in the subcortical habitats; none feeds on adults. They are relatively "venomless" and the host remaining alive for about a day after the initial attack (Cross and Moser, 1975).
Species of the ventricosus group are not known to be phoretic, and thus females are monomorphic. At least some species possess venom. The mites inject venom into prey, which causes paralisis and eventual death (Krczal, 1957). The host range includes a variety of hosts, and some species even attack and feed on pupae and adult insects. The bites of Pyemotes tritici (Lagrèze-Fossot et Montané, 1851) can cause severe dermatitis on people handling infested material such as hay. Contact with this mite can also produce asthma or nausea.
Records of Pyemotes from bees include Pyemotes ventricosus (Newport, 1850) from Anthophora retusa (Linnaeus, 1758) (Apidae) in England (Newport, 1850), Pyemotes anobii Krczal, 1957 from a colony of the European honey bee, Apis mellifera Linnaeus, 1758 (Apidae) in the United States (Cross and Moser, 1975), Pyemotes beckeri Krczal, 1957 (as ventricosus) from laboratory cultures of megachilid bees (Krombein, 1967), and Pyemotes herfsi (Oudemans, 1936) from hives of Apis cerana Fabricius, 1793 in India (Dinabandhoo and Dogra, 1982). In the latter case, the mites were considered as pests. Nogueira-Neto (1997) mentioned that representatives of genus Pyemotes can destroy entire colonies of stingless bees in Brazil.
Pyemotes ventricosus, the type species of the genus, is poorly described and probably has been misidentified by subsequent workers. Oudemans (1937) speculated that the fungal disease of the bee larvae reported by Frison (1923) for Anthophora abrupta Say, 1837 in the United States, is in fact physogastric females of Pyemotes ventricosus. Cross and Moser (1975) suggested that this species is only known from the original description and has never been recollected.
Current knowledge of the morphology, ecology, and distribution of North American Pyemotes associated with bees is summarized in the key below:

Key to species of Pyemotes found on bee in North America
males*

1. Hysterosomal setae c₂ large, similar to d or e in size. Setae ip vestigial. Third prodorsal setae approximately twice as long as second prodorsal setae. On larvae of Anobiidae, Curculionidae, Buprestidae, Scolytidae, and Lyctidae (Coleoptera), vespid and sphecid wasps; laboratory colonies of megachilid bees. Holarctic ... Pyemotes beckeri
- Hysterosomal setae c₂ distinctly smaller than d or e. Length of third and second prodorsal setae variable.
2(1). Setae c of femur IV short and slender, rarely reaching tip of tarsus IV, less than half as long as opisthosomal setae d and e. Third prodorsal setae not exceeding length of second prodorsal setae. Setae ip vestigial. On larvae of Anobiidae, Curculionidae, Buprestidae, Scolytidae (Coleoptera); colony of Apis mellifera. Holarctic ... Pyemotes anobii
- Setae c of femur IV long and stout, extending at least to, and usually beyond tarsus IV, more than half as long as opisthosomal setae d and e. Third prodorsal setae approximately twice as long as second prodorsal setae. Setae ip filiform, nearly as long as ax2. Nests of Hoplitis (Megachilidae) in Colorado ... Pyemotes sp.

* Modified from Cross et al. (1981). In all species in the key the fourth prodorsal pair of setae being distinctly thinner than setae d and e.

Pyemotes beckeri Krczal, 1957

Pyemotes beckeri Krczal, 1957: 451, Figs 28-30; Cross and Moser, 1975: 734; Cross et al., 1981: 181.
Pyemotes ventricosus (non Newport, 1850): Krombein, 1967: 369.

Biology. In the United States this species was recorded from Lyctus planicollis LeConte, 1858 (Coleoptera: Lyctidae) in Mississippi, Scolytus multistriatus (Marsham, 1802) (Scolytidae) in Louisiana, and a wasp nest in Virginia (Arlington) (Cross and Moser, 1975). Krombein (1967) reported "Pyemotes ventricosus" from an array of sphecid and vespid wasps, as well as from nests of megachilid bees infested in the laboratory. Because his material included numerous samples from nests of wasps from Arlington (Virginia), and Cross and Moser (1975) reported Pyemotes beckeri from a wasp nest from exactly the same locality, we assume that Krombein's material in fact was misidentified. Unfortunately, without Krombein's material we can not confirm this assumption or check whether it is represented by one or more species. Unverified records of Pyemotes beckeri from North American Hymenoptera include Tripargilum clavatum (Say, 1837) (Maryland, New York, Virginia), Tripargilum tridentatum tridentatum (Packard, 1867), Tripargilum tridentatum archboldi (Krombein, 1959) (Florida), Trypoxylon frigidum Smith, 1856 (Virginia), Psenulus pallipes parenosas (Pate, 1944) (Virginia) (Sphecidae), Stenodynerus krombeini Bohart, 1953 (New York), Euodynerus foraminatus apopkensis (Robertson, 1901) (Virginia) (Vespidae), Prochelostoma philadelphi (Robertson, 1891) (Virginia, infested in laboratory), Aschmeadiella bigeloviae (Cockerell, 1897) (Arizona, infested in laboratory), Aschmeadiella bucconis denticulata (1878) (Arizona, infested in laboratory), Osmia pumila Cresson, 1864 (infested in laboratory, the nest is probably from Maryland) (Megachilidae) (Krombein, 1967).
Outside North America, this species was found on larvae of Anobium punctatum (De Geer, 1774) (Coleoptera: Anobiidae), Sitophilus granarius (Linnaeus, 1758), and Sitophilus oryzae (Linnaeus 1763) (Curculionidae) in Germany (Krczal, 1957).
Krombein (1967) noted that "normal" females move relatively rapidly. They are able to leave an infested nest after the host insects have been killed, and enter adjacent nests through the breached entrance plugs and cell partitions. The mites attack eggs, larvae, pupae, as well as paralyzed prey stored by wasps (insects and spiders). This species of Pyemotes can cause serious problems in laboratory settings, as mite females can easily infest cultures of bees through the split halves of the trap nests
Distribution. USA: Arizona, Florida, Louisiana, Maryland, Mississippi, New York, and Virginia; Germany (type locality) (Cross and Moser, 1975; Krczal, 1957; Krombein, 1967).
Hosts. See above.

Pyemotes anobii Krczal, 1957

Pyemotes anobii Krczal, 1957: 444, Figs. 22-2; Cross and Moser, 1975: 724; Cross et al., 1981: 182.

Biology. Found parasitizing larvae of a range of Coleopteran hosts (see below), also found in a colony of the European honeybee Apis mellifera in the United States (California) (Cross and Moser, 1975).
Distribution. USA: California, Georgia, Louisiana; Germany (type locality); Denmark (Krczal, 1957; Cross and Moser, 1975).
Hosts. Originally described from a culture of Anobium punctatum (De Geer, 1774) (Coleoptera: Anobiidae), also reproduced on pupae and larvae of Sitophilus granarius (Linnaeus, 1758) and Sitophilus oryzae (Linnaeus, 1763) (Curculionidae) in Germany (Krczal, 1957). In the United States it was found on Phloeotribus dentifrons (Blackman, 1921) (Scolytidae), Agrilus lecontei Saunders 1871 (Buprestidae), and Apis mellifera (Hymenoptera: Apidae) (Cross and Moser, 1975).

Physogastric females of mite Pyemotes sp. (Pyemotidae) parasitizing pupa of the bee Hoplitis fulgida fulgida (Hymenoptera: Megachilidae).

Fig. 2. Physogastric females of the mite Pyemotes sp. (Pyemotidae) parasitizing pupa of the bee Hoplitis albifrons argentifrons (Hymenoptera: Megachilidae) from Colorado. Click here to enlarge

Pyemotes sp.

Material. 3 males, 7 females - USA: Colorado, Boulder Co., Eldorado Canyon State Park, Crescent Meadows, elev. 1985 m, Hoplitis fulgida fulgida (Cresson, 1864) (Hymenoptera: Megachilidae) trapnest (brought indoors 16 Apr 1997), 5 May 1997, V. Scott 1996-034-8, UMMZ BMOC 97-1010-001; 4 males, 6 females - same locality, elev. 1985 m, Hoplitis sp. (Hymenoptera: Megachilidae) trapnest (brought indoors 21 Apr 1997), 5 May 1997, V. Scott 1996-124-1, UMMZ BMOC 97-1010-004; 9 males, 6 females - same locality, elev. 1955 m, trapnest (brought indoors 21 Apr 1997), 5 May 1997, V. Scott 1996-115-1, UMMZ BMOC 97-1010-003.
Biology. Found parasitizing pupae of Hoplitis sp.
Distribution. USA: Colorado.
Hosts. Hoplitis fulgida.
Notes. Males are similar to Pyemotes herfsi (Oudemans, 1936) as diagnosed by Cross et al. (1981), p. 182, couplet 14. Our species differs by the fourth propodosomal pair of setae being distinctly thinner than setae d and e (stout, as thick as setae d and e in P. herfsi).

References

Cross E. A. 1965. The generic relationships of the family Pyemotidae (Acarina: Trombidiformes). The University of Kansas Science Bulletin. 45(2): 29-275.

Cross E. A. and Moser J. S. 1975. A new, dimorphic species of Pyemotes and a key to previously-described forms (Acarina: Tarsonemoidea). Annals of the Entomological Society of America. 68(4): 723-732.

Cross E. A., Moser J. C. and Rack G. 1981. Some new forms of Pyemotes (Acarina: Pyemotidae) from forest insects, with remarks on polymorphism. International Journal of Acarology. 7: 179-196.

Dinabandhoo C. L. and Dogra G. S. 1982. The Pyemotids (Aacrina: Pyemotidae) and their significance in apiculture. Indian Bee Journal. 44(2): 29-32.

Frison T. H. 1922. Notes on the life history, parasites and inquiline associates of Anthophora abrupta Say, with some comparisons with the habits of certain other Anthophoridae (Hymenoptera). Transactions of the American Entomological Society. 48(2): 137-156.

Kethley, J. 1982. Prostigmata. In: S. P. Parker [Ed.] Synopsis and Classification of Living Organisms. McGraw-Hill, New York. 117-145 pp.

Krczal, H. 1957. Sytstematik und Ökologie der Pyemotiden. In: H.-J. Stammer [Ed.] Sytstematik und Ökologie Mitteleuropäischer Acarina. 1(1). Akademissche Verlaggesellschaft, Leipzig: 385-823.

Krczal, H. 1959. Pyemotes boylei, eine neue Pyemotidae aus Hawaii. Zoologischer Anzeiger. 163: 148-152.

Krombein, K. 1967. Trap-nesting wasps and bees: life histories, nests, and associates. Smithsonian press: Washington, D.C. 570 pp.

Lindquist E. E. 1986. The world genera of Tarsonemidae (Acari: Heterostigmata): A morphological, phylogenetic, and systematic revision, with a reclassification of family-group taxa in the Heterostigmata. Memoirs of the Entomological Society of Canada. 136: 1-517.

Newport G. 1885. Further observations on the habits of Monodontomerus; with some account of a new Acarus (Heteropus ventricosus), a parasite in the nests of Anthophora retusa. The Transactions of the Linnean Society of London. 21(2): 95-102.

Nogueira-Neto P. 1997. Vida e criação de abelhas sem ferrão [=Life and origin of stingless bees]. Editora Nogueirapis. 446p.

Oudemans A. C. 1937. No title. Tijdschrift voor Entomologie. 80: IV-XVI.

Walter D. E., Beard J. J., Walker K. L. and Sparks K. 2002. Of mites and bees: A review of mite-bee associations in Australia and a revision of Raymentia Womersley (Acari: Mesostigmata: Laelapidae), with the description of two new species of mites from Lasioglossum (Parasphecodes) spp. (Hymenoptera: Halictidae). Australian Journal of Entomology. 41: 128-148.