The bat skin mites from the closely-related Demodecidae and Psorergatidae families occur synhospitally, populating the same host species and perhaps neighboring microhabitats. However, data on their occurrence and parasitism are fragmentary and dispersed. Thus far, 27 Demodecidae and 18 Psorergatidae species have been described, but the coexistence of mites from both families was only demonstrated in six species of bats. This article presents a description of Demodex pusillus sp. nov. from Nyctalus noctula, including a new host record (first observation of demodecid mites in Nyctalus) and a new record concerning the occurrence of Psorergatoides kerivoluae in Plecotus auritus. It also includes an updated global checklist of the occurrence of Demodecidae and Psorergatidae in Chiroptera, including data on their records/distribution and location in their hosts. In both studied families, the mites exhibit preferences, and even topographic specificity, colonizing different microhabitats in the host, including the eye region (e.g., Meibomian glands of the eyes, corneal surface and eyelid vault), wing membranes and hairy skin on the body. Such colonization of separate microhabitats enables different species to co-occur within the same host, while the total number of parasites determines the level of parasite load, with higher levels being associated with the incidence of disease symptoms. It is worth mentioning that Demodex pusillus sp. nov. is the smallest known representative of the Demodecidae family and one of the smallest animals (70–80 micrometers in length).

The fossil record reveals palaeoecological interactions between plants and insects. This study describes a singular conifer xylite specimen from the Baltic amber-bearing deposits, with preserved resin ducts and cylindrical insect borings designated as Bivium ichnogen. nov. with Bivium diluviandi ichnosp. nov. The borings, characterized by longitudinal tunnels connected by cross tunnels and chambers, were likely created by xylophagous beetles belonging to the family Curculionidae (subfamily Scolytinae). The associated resin production reflects an adaptive plant response to insect and fungal activity, evidenced by fungal hyphae preserved within the specimen. This work contributes to the knowledge of Baltic amber stratigraphy, and the formation of resin-bearing deposits, and shows, that the wood-boring insects may have been a cause, among others, of resin exudation.

Only six parasitic species of Demodecidae mite have thus far been described from the Soricomorpha, these being associated with the common shrew Sorex araneus Linnaeus, 1758, and the Mediterranean water shrew Neomys anomalus Cabrera, 1907 (two species from each host), and with the lesser white-toothed shrew Crocidura suaveolens (Pallas, 1811) and the European mole Talpa europaea Linnaeus, 1758 (one from each host species). Presently, Demodex crocidurae, a new species, has been described from the territory of Poland for C. suaveolens; in order to confirm its validity, it was necessary to redescribe D. talpae Hirst, 1921, from T. europaea, a demodecid species first described by Hirst in 1921 from England and then noted only in Poland. Both species colonized the hairy skin of the body in their hosts, where no disease symptoms of infestation were observed. However, D. crocidurae showed higher infection parameters (prevalence 100%, mean intensity 11.7, intensity range 3–26 individuals) than those of D. talpae (30.0%, 4.7, 2.0–8.0), possibly due to different host biology.

Piddocks (Pholadidae) are bivalves adapted for boring in substrates such as wood, rocks, and fossil resins. While the trace fossils associated with their boring behavior (Teredolites and Apectoichnus) are well documented, their body fossils are much rarer in the fossil record, particularly as amber inclusions. This work reports inclusions of fossilized piddocks and the first known barnacle inclusions from the Early Miocene simojovelite (Chiapas amber). We examined seven amber specimens containing over 90 piddock inclusions, representing at least five distinct morphotypes. The amber preserved various developmental stages, from juveniles with open pedal gaps to fully mature individuals with well-developed accessory plates. Taphonomic analysis, observed orientations, and the presence of diagenetically altered inclusions suggest that these piddocks inhabited waterlogged wood of Hymenaea and possibly semi-hardened resin before entrapment. This study highlights fossil resins as an overlooked preservational medium for marine invertebrates, providing new data on piddock behavior, fossil resin taphonomy, and the Miocene coastal environments of the Chiapas region.

Mites from the Demodecidae and Psorergatidae can optimally use mammalian hosts by inhabiting a number of different microhabitats in their skin. Hence, in individual hosts, several species of parasites from these groups have been described in different microhabitats. There are few data on their co-occurrence either at the host species level or at the host individual level. Most research has addressed the co-occurrence of Demodecidae in carnivorans, ungulates, soricomorphs, and rodents, while the co-occurrence of both families was found in bats. The present study examines the possibility of their co-occurrence in a Eurasian rodent—Apodemus flavicollis. It is a suitable model for such analyses, because representatives of both families have been demonstrated here so far, and our findings extend the list of specific Demodecidae in A. flavicollis with two new species: Demodex tenuis sp. nov. from the lip region and D. mediocris sp. nov. from the chin region. The study also includes the first record of Psorergates muricola in this host, which occurred in the genital–anal region. Therefore, the findings confirm the possibility that different Demodecidae and Psorergatidae species can co-occur in the same host in different body regions. This paper also includes a checklist of Demodecidae and Psorergatidae in rodents around the world.