Phoresy is an ecological interaction that occurs between two species of different sizes. The smaller species (phoront) attaches itself to the larger organism (host), which the phoront uses as a means of transport (Vachon Reference Vachon1940; Bartlow and Agosta Reference Bartlow and Agosta2021). In this way, phoronts belonging to groups with limited capacity for movement outside a restricted range can greatly increase their distribution, limited only by their host’s vagility (Guzmán-Vásquez et al. Reference Guzmán-Vásquez, Villegas-Guzmán and Martínez-Martínez2025). They strategically take advantage of their host to disperse and colonise new habitats, thereby acquiring resources that ensure their own survival and that of their progeny (Bartlow and Agosta Reference Bartlow and Agosta2021; Martínez et al. Reference Martínez, Villegas-Guzmán, Mendoza and Quirós2024; Guzmán-Vásquez et al. Reference Guzmán-Vásquez, Villegas-Guzmán and Martínez-Martínez2025). A potential benefit that the phoront might obtain at the expense of its host is protection and temporary refuge from predators and adverse environmental conditions. However, according to Luong et al. (Reference Luong, Penoni, Horn and Polak2015) and Hicks et al. (Reference Hicks, Burthe, Daunt, Butler, Bishop and Green2018), phoresy, traditionally conceptualised as a neutral or commensal ecological interaction, can generate significant physiological, energetic, and functional costs for hosts, depending on the ecological context, the phoretic load, and the physiological state of the host. The above relationship highlights the complexity and multifaceted nature of phoresis because this form of interaction transcends mere transportation, encompassing intricate ecological dynamics such as the synchronisation of life cycles (Castillo and Villegas-Guzmán Reference Castillo and Villegas-Guzmán2016). This phenomenon carries profound implications for the coevolutionary history of these organisms (Bartlow and Agosta Reference Bartlow and Agosta2021; Martínez et al. Reference Martínez, Villegas-Guzmán, Mendoza and Quirós2024).

Pseudoscorpions are capable of firmly grasping the hairs, setae, antennae, or legs of their host with their pedipalps. This behaviour is referred to as active phoresy. However, they have also been observed inside the cavities of their host’s wings and elytra, a phenomenon referred to as passive phoresy (Vachon Reference Vachon1940; Castillo and Villegas-Guzmán Reference Castillo and Villegas-Guzmán2016).

Several species of the genus Lustrochernes Beier (Pseudoscorpiones: Chernetidae) have been documented as phoronts of at least six families of Coleoptera: Cerambycidae, Curculionidae, Elateridae, Passalidae, Staphylinidae, and most recently, Scarabaeidae (Castillo and Villegas-Guzmán Reference Castillo and Villegas-Guzmán2016; Villegas-Guzmán et al. Reference Villegas-Guzmán, Martínez-Luque and Zurita-García2016; Viggers-Carrasco et al. Reference Viggers-Carrasco, Sánchez-Alfaro, Villegas-Guzmán, Ruiz-Herrera and Rodríguez-Maturino2020; Marra and Fischer Reference Marra and Fischer2023; Guzmán-Vásquez et al. Reference Guzmán-Vásquez, Villegas-Guzmán and Martínez-Martínez2025). Lustrochernes grossus (Banks) is phoretically associated with at least nine species of Coleoptera, including Tragosoma spiculum Casey; Trichocnemis spiculatus neomexicanus (Casey) (Cerambycidae); Heliscus tropicus (Percheron); Odontotaenius striatopunctatus (Percheron); Passalus interstitialis Eschscholtz; P. punctatostriatus Percheron (all Passalidae); Chalcolepidius sp.; C. approximatus Erichson; and C. virginalis (Candeze) (Elateridae) (Muchmore Reference Muchmore1991; Poinar et al. Reference Poinar, Curcic and Cokendolpher1998; Villegas-Guzmán et al. Reference Villegas-Guzmán, Martínez-Luque and Zurita-García2016; Viggers-Carrasco et al. Reference Viggers-Carrasco, Sánchez-Alfaro, Villegas-Guzmán, Ruiz-Herrera and Rodríguez-Maturino2020).

The objectives of the present work are to report for the first time the phoretic interaction between Lustrochernes grossus and Mallodon dasystomum (Say) (Coleoptera: Cerambycidae) and to provide a checklist of species of the family Cerambycidae that have been recorded as hosts of phoretic pseudoscorpions.

On 18 May 2025, a longhorn beetle was collected in a residential backyard located in the municipality of Zaachila, Oaxaca, Mexico (16° 57′ 27″ N, 96° 44′ 56″ W; 1510 m above sea level; Fig. 1). Adjacent to the collected site is a property with a large pecan walnut tree, Carya illinoinensis (Wangenheim) K. Koch (Juglandaceae). The beetle was preserved in a vial with 70% ethyl alcohol. After the beetle was placed in alcohol, it was observed that pseudoscorpions were detaching from it. Consequently, a meticulous examination of the underside of the elytra was conducted, where more pseudoscorpions were found (Fig. 2A).

Figure 1.

Location of the Mallodon dasystomum collection site in Oaxaca, Mexico.

Figure 2.

Phoretic association between Lustrochernes grossus and Mallodon dasystomum: A, pseudoscorpions below the right elytra of the beetle; B, dorsal view of adult M. dasystomum; C, pupa of M. dasystomum; and D–E, third-instar larva of M. dasystomum.

The beetle was mounted on an entomological pin (Fig. 2B) and identified using specialised literature (Lingafelter Reference Lingafelter2008; Monné et al. Reference Monné, Monné, Wang and Wang2017) and by comparing it with photographs of type specimens of some synonyms in Bezark (Reference Bezark2026). The pseudoscorpions were processed following the technique of Hoff (Reference Hoff1949), with the modifications of Wirth and Marston (Reference Wirth and Marston1968). Identification to genus was performed using the keys of Muchmore (Reference Muchmore and Dindal1990), and that to species was performed using the works of Beier (Reference Beier1932) and Chamberlin (Reference Chamberlin1938). The measurement was conducted according to the method of Chamberlin (Reference Chamberlin1931); only the chelae were measured, employing the modifications devised by Benedict and Malcolm (Reference Benedict and Malcolm1977). The pseudoscorpions were deposited in the Arachnid Collection of the Escuela Nacional de Ciencias Biológicas of the Instituto Politécnico Nacional (México City, México), and the beetle was deposited in the first author’s (H.M.G.V.–Zaa.) reference collection.

A comprehensive literature search was conducted to determine the number of species of longhorn beetles and pseudoscorpions that are associated phoretically. The nomenclature of the beetles was verified against the Titan database (Tavakilian and Chevillotte Reference Tavakilian and Chevillotte2025), and the nomenclature of the pseudoscorpions was verified against the World Pseudoscorpions Catalog (2022).

Five pseudoscorpions (5♀) of the species L. grossus were found performing passive phoresis (Fig. 2A) as they were travelling under the elytra of M. dasystomum. This behaviour has been documented as a general tendency in species of Lustrochernes, particularly in L. grossus. These pseudoscorpions have been frequently reported to travel beneath the elytra of their hosts (Aguiar and Bührnheim Reference Aguiar and Bührnheim1992; Castillo and Villegas-Guzmán Reference Castillo and Villegas-Guzmán2016; Villegas-Guzmán et al. Reference Villegas-Guzmán, Martínez-Luque and Zurita-García2016, Reference Villegas-Guzmán, Ramírez-Hernández, Escobar and Almendarez2022; Viggers-Carrasco et al. Reference Viggers-Carrasco, Sánchez-Alfaro, Villegas-Guzmán, Ruiz-Herrera and Rodríguez-Maturino2020; Marra and Fischer Reference Marra and Fischer2023). In addition, one of the pseudoscorpions was observed to be attached to the left membranous wing of the beetle (Fig. 2A).

Based on the literature, the present study constitutes the first documentation of the association between these two species. Before the present study, the only documented cases of phoresis in the genus Mallodon were observed in two species: M. spinibarbis (Linnaeus) with the pseudoscorpions Lechytia chthoniiformis Balzan (Lechytiidae), Lustrochernes sp., Lustrochernes intermedius (Balzan) (Chernetidae), and Neocheiridium corticum (Balzan) (Cheiridiidae) (Aguiar and Bührnheim Reference Aguiar and Bührnheim1998; Marra and Fischer Reference Marra and Fischer2023), and M. chevrolatti (Thomson) with Americhernes oblongus (Say) (Chernetidae) (Martínez et al. Reference Martínez, Villegas-Guzmán, Mendoza and Quirós2024).

In summary, including the present phoresis record, 26 species of Cerambycidae are now known to be associated with at least 24 species of five families of pseudoscorpions (Atemnidae, Cheliferidae, Chernetidae, Cheiridiidae, and Lechytiidae). Among these families, Chernetidae has the highest number of recorded interactions, with 12 species associated with 16 species of cerambycids (Table 1).

Table 1.

Cerambycidae species associated with phoretic pseudoscorpions. Names placed after the symbol = correspond to synonyms.

The larvae and adults of Mallodon dasystomum have been observed to inhabit tree trunks and stumps. The larvae construct galleries that facilitate feeding and provide protection during pupation (see Fig. 2C–E). This same behaviour has been documented for M. spinibarbis and M. chevrolati (Marra and Fischer Reference Marra and Fischer2023; Martínez et al. Reference Martínez, Villegas-Guzmán, Mendoza and Quirós2024). In the municipality of Zaachila, M. dasystomum individuals have been commonly found in the trunks of pecan walnut, guamuchil, Pithecellobium dulce (Roxburgh) Bentham (Fabaceae), and zompantle, Erythrina coralloides de Candolle (Fabaceae), trees (Fig. 2C–E).

The proximity of a pecan walnut tree to the collection site suggests the possibility of beetle migration from this location to the house where the specimen was collected. This migration may have been triggered by the presence of lights in the house the previous night. Consequently, it is plausible that the association between the beetle and the pseudoscorpions occurred in the walnut tree because this is a resource they share. The extant literature on the subject is abundant and well documented. Lustrochernes grossus, as well as other species of the genus, has been observed to inhabit the undersides of tree bark (Castillo and Villegas-Guzmán Reference Castillo and Villegas-Guzmán2016; Villegas-Guzmán et al. Reference Villegas-Guzmán, Martínez-Luque and Zurita-García2016, Reference Villegas-Guzmán, Ramírez-Hernández, Escobar and Almendarez2022).