Coleoptera (Annex II and Annex III)

K, Julia Baumann, 2024, An update on the knowledge about scutacarid mites as phoronts and inquilines, Acarologia 64 (1), pp. 3-17 : 5-7

Coleoptera (Annex II and Annex III)

Within Coleoptera , the by far largest number of associated scutacarids can be found in the family Carabidae (Baumann 2018) . However, since 2017, only three scutacarid species have been reported from carabid beetles (see Annex II), and only one of these reports is worth mentioning here: Heterodispus turkmenistaniensis Khaustov & Chydyrov, 2005 was encountered in Iran

on the beetle Scarites (Scarites) procerus eurytus ( Sobhi et al. 2017a) , and this is the first

report of the carabid subfamily Scaritinae as hosts for Scutacaridae . The authors found H. turkmenistaniensis also on beetles belonging to the family Tenebrionidae , and it was also reported on Scarabaeidae (see below). Until now, this scutacarid species was only known from soil samples.

Two new species of Scutacaridae associated with two other beetle families have been described: Archidispus hydrophilus Khadem-Safdarkhani & Hajiqanbar, 2022 was found attached to Coleostoma fabricii ( Hydrophiliidae ; see Annex III) on its hosts sternite between

the coxae ( Khadem-Safdarkhani et al. 2022). This beetle feeds on decomposing material below

wet rocks or among grass roots. This material supposedly is an ideal substrate for the growth of

fungal mycelia, which in turn are a likely food source for the mite ( Khadem-Safdarkhani et al.

2022). In the family Curculionidae (see Annex III), Scutacarus pseudoplurisetus Khaustov,

2017 was described from the wood borer Ips typographus ( Khaustov 2017b and Khaustov et

al. 2018b), a species which has already been noted as host for two scutacarid species before

(Baumann 2018). The total number of scutacarid species associated with I. typographus now

went up to five as Khaustov (2017b), and Khaustov et al. (2018b) also reported Scutacarus

palustris Rack, 1966, a species also associated with ants and rodents (Baumann 2018), and

Scutacarus muscocicola Sevastianov, 1983 , which had until now only been reported from moss

and litter, on this beetle. All five species associated with I. typographus belong to the genus

Scutacarus .

In the family Scarabaeidae , three new genera have been reported as a new host for

scutacarids: the genus Adoretus for Heterodispus turkmenistaniensis , the genus Hybalus for

Pygmodispus odontotarsus Sevastianov, 1975 ( Khaustov and Frolov 2018), and the genus

Oryctes for Scutacarus longitarsus (Berlese, 1905) ( Rahiminejad et al. 2020a, 2023).

All three scutacarid species appear to be generalists in terms of habitat and/or host range,

as P. odontotarsus has already been reported from the nest of a small mammal and from soil,

S. longitarsus has been found on dipterans and various families of coleoptera (Baumann 2018

and this publication) and H. turkmenistaniensis on different coleoptera families and from soil

(this publication).

Imparipes (Sporichneuthes) intermedius Paoli, 1911 , a species until now only known from

soil and litter, has now also been encountered on different scarab beetles ( Rahiminejad et al.

2020a)

Furthermore, six new beetle families have been identified as hosts for Scutacaridae :

Cerambycidae , Dryopidae , Elateridae , Geotrupidae , Lucanidae and Meloidae (see Annex III).

In Cerambycidae , Scutacarus hystrichocentrus Sevastianov, 1983 was encountered on the

beetle Paranda caspia by Hajiqanbar and Arjomandi (2019). This beetle attacks dead host

plants which had already been infested by wood boring insects, and the authors conclude that the

dead wood presumably is a suitable habitat for scutacarid mites. Until now, S. hystrichocentrus

was only known as associate of ants of the genus Lasius (see Baumann 2018).

In the family Dryopidae , the genus Dryops has been reported as new host for Scutacarus

sphaeroideus Karafiat, 1959 ( Rahiminejad et al. 2020b, 2023). About 75% of dryopid species

are aquatic (Khagani et al. 2022), but although no nearer information was available, it is

most probable that S. sphaeroideus was attached to one of the remaining riparian or terrestrial

species.

Beetles of the family Elateridae were identified as new hosts for Archidispus insolitus

(Kurosa, 1974) and Imparipes (I.) moderatus Khaustov, 2008 . Archidispus insolitus , until now

only known from Carabidae (Baumann 2018) , has also been found on Meloidae (see below),

Tenebrionidae and Scarabaeidae ( Rahiminejad et al. 2023) . Imparipes (I.) moderatus was

encountered on Drasterius bimaculatus by Navabi et al. (2018a). This scutacarid species was

until now only known as associate of ants (Baumann 2018). Drasterius bimaculatus adults live

on the ground of many different terrestrial habitats including riverside alluvial soils, whereas

their larvae are rhizophagous ( Gradinarov 2003, Hardersen et al. 2012). The high mobility of

the adults as well as the rhizophagous lifestyle of the larvae most likely make these beetles an

attractive host for scutacarids.

In Geotrupidae , Geotrupes spiniger was determined as host for Scutacarus longitarsus

by Rahiminejad et al. (2020a). This species builds brood chambers that are filled with dung

( Klemperer 1979), which most likely facilitates the growth of fungi and thus allows scutacarids

to thrive there.

Lucanus ibericus of the family Lucanidae has also been newly reported as host for

Scutacarus longitarsus ( Rahiminejad et al. 2020a, 2023). The larvae of lucanid beetles live in

decayed wood, a suitable habitat for scutacarids.

Finally, the family Meloidae has been listed as a new host for Archidispus insolitus ( Rahiminejad et al. 2023) . Adult beetles are mostly phytophagous, but their juvenile stages

are often associated with solitary hymenopterans and complete their metamorphosis in soil (Ghahari & Campos-Soldini 2019), which could explain the association of the scutacarids with these beetles.