Lapidisma, Molero-Baltanás & Zúñiga-Reinoso & Gaju-Ricart & Predel, 2025

Molero-Baltanás, Rafael, Zúñiga-Reinoso, Álvaro, Gaju-Ricart, Miquel & Predel, Reinhard, 2025, Morphological and molecular revision of the subfamily Heterolepismatinae (Zygentoma, Lepismatidae), with descriptions of two new genera from the Atacama Desert, Chile, ZooKeys 1260, pp. 233-278 : 233-278

Lapidisma gen. nov.

Type species.

Lapidisma paposanum sp. nov.

Diagnosis.

Medium-sized silverfish (adults reaching 7.0– 8.5 mm). Body shape fusiform, with thorax slightly wider than the abdomen base. Antennae as long as body or a little longer; caudal filaments slightly shorter than body. Epidermal pigment present, dorsal scales pigmented. Multi-radiate orbicular scales, rounded to subquadrangular, covering the body dorsally and ventrally, also present on coxae and clypeus. Scales of femora and tibiae ovoid, wide, smaller than those of coxae and body, with their base not orbicular (not surrounding the socket). Subtriangular apically truncate scales present on scape and pedicel of antennae and basal articles of maxillary palps; some scales showing this shape are also present on femora. Scales absent from labrum, apical articles of maxillary palps, labial palps, tarsi, and abdominal styli; caudal filaments with some narrow lanceolate scales. Macrochaetae smooth, apically bifurcate. Compound eyes with 12 ommatidia. Frontal chaetotaxy concentrated on lateral parts, with a wide gap in the middle. Clypeus almost vertical, with 1 + 1 lateral tufts of macrochaetae and rounded scales. Labrum folded backwards, with a transverse group of macrochaetae not forming clear lateral tufts. Antennae with trichobothria and also with chaetic, trichoid, coeloconic and several types of basiconic sensilla. Galea with a small apical peg. Maxillary palp with the apical article bearing basiconic sensilla types B and C, and a longitudinal row of three styloconic sensilla. Apical article of the labial palp with five typical papillae arranged in a jagged line, not clearly forming two lines, nor a straight one; the outer lateral area with basiconic sensilla types B and C. Anterior margin of pronotum with setal collar. Lateral margins of thoracic nota with several macrochaetae, most of them isolated, in some places forming implied combs of two macrochaetae; posterior margin devoid of setae. Trichobothrial areas open, Type 1 according to classification of Mendes (1986). Thoracic sternites parabolic, with convex or slightly truncated hind margin. Coxae with a row of macrochaetae on their anterior margin and on the posterior margin. Metatibiae bearing a long anterior trichobothrium. Tarsi with four articles; pretarsal claws typical, with a short striated medial empodial claw. Urotergites I-VIII with 3 + 3 combs of macrochaetae; those at submedian position can consist of 1–2 + 1 – 2 macrochaetae (when two are present, they are inserted very close together and arranged obliquely to the posterior margin of the tergite). Urotergite IX devoid of setae. Urotergite X short trapezoidal, with hind margin almost straight or with its median part slightly convex, with several setae on their lateral margins, lacking combs. Urosternite I without setae. Urosternites II-VIII in male and II-VII in female with 1 + 1 single macrochaetae; each coxite VIII of females also with only one isolated macrochaeta. Four pairs of abdominal styli in both sexes. Parameres ovoid or short subcylindrical, with a division delimiting an apical part with some glandular setae. Females with a thin ovipositor of the primary type.

Remarks.

The combination of characters indicated in the diagnosis of this genus is more similar to those shared by the Australian species included in the genus Visma than to those shared by Australian taxa included in Heterolepisma . As the name Visma is pre-occupied (see Introduction), the new name assigned here to this genus of Lepismatidae is Vistrolepisma nom. nov.; the prefix ‘ Vistro’ - refers to vistrum, a name for a cephalic ‘ visor’ consisting of frontal scales, which inspired Smith et al. (2021) to use the name Visma for this genus.

Comparison with South American species assigned to Heterolepisma is more difficult since specimens in good conditions belonging to these American taxa are not available, with the exception of a recently collected Heterolepisma from Argentina that is treated here as H. andinum . Similarities and differences with other taxa of Heterolepismatinae are presented in Tables 2 , 3 . We emphasise that, like Vistrolepisma , Lapidisma gen. nov. has bifid macrochaetae on labrum, scales on scapus, three slender styloconic sensilla in the apical article of maxillary palp, wide scales on femora and tibiae, and short urotergite X, but it differs from Vistrolepisma in lacking 1 + 1 posterior macrochaetae on the hind margins of thoracic nota, the convex shape of thoracic sternites (truncate in Vistrolepisma ), a higher number of macrochaetae on infralateral combs, the shape of clypeal scales and the presence of 3 + 3 combs on urotergite VIII (2 + 2 in Vistrolepisma in this position), although the submedian combs of this urotergite can be reduced to one or two macrochaetae. Looking for affinities with other South American species previously described and comparing the new taxon from Atacama Desert with the species geographically found in the Southern Cone, which is the topotypic area of Heterolepisma sensu stricto (s. str.), such as H. andinum and H. pampeanum , we can clearly distinguish the new taxon from both species because it has a higher number of styli (one pair in H. andinum and two pairs in H. pampeanum ). Moreover, H. andinum is different from Lapidisma gen. nov. because the latter has only 1 + 1 lateral macrochaetae on urosternites and H. andinum bears 1 + 1 lateral combs of several macrochaetae, 4–6 according to Stach (1933); H. pampeanum is similar in this character to the new species from Atacama Desert. Other characters that have proven to be relevant for generic diagnosis, such as trichobothrial areas, distribution, and shape of scales on appendages, shape and chaetotaxy of thoracic sternites, cephalic chaetotaxy, etc., were not mentioned in the original descriptions of these species or in later published manuscripts that listed some additional characters of the Argentine species ( Stach 1933; Wygodzinsky 1948). However, examination of the specimen collected in Argentina, which corresponds to H. andinum in the number of styli and abdominal chaetotaxy, suggests that this species probably belongs to a different genus, as it differs from Lapidisma gen. nov. in the shape and distribution of scales on appendages, cephalic and ventral chaetotaxy, among other things (see Tables 2 , 3 ). It is likely that most characters of H. andinum are shared with H. pampeanum , the type species of the genus Heterolepisma , although this requires examining the types of this species or, at least, some material identified by experts (such as P. Wygodzinsky) as this species. This could confirm our hypothesis that Heterolepisma s. str. is endemic to the eastern side of the Andean mountain range, and that the Andean biogeographic barrier separates Heterolepisma s. str. from the Chilean genera described in this work. A re-examination of H. annectens from Juan Fernandez Islands may clarify whether this species should be assigned to Lapidisma gen. nov., since some shared characters, such as the number of styli, the large size of parameres, and the absence of chaetotaxy on the hind margins of thoracic nota, support this hypothesis. We propose that this species can be considered as Lapidisma annectens comb. nov. Compared to L. annectens , L. paposanum sp. nov. has a higher number of macrochaetae on infralateral combs, but other differences cannot be established because the incomplete description of Silvestri (1902).

Etymology.

This generic name is a fusion of the words lapidum and lepisma, this latter used for most genera of silverfish belonging to the family Lepismatidae . Lapidum is the genitive plural form of lapis, a Latin word that means stone, and refers to the usual habitat of this insect, which is found associated with stones, usually under them. Thus, the literal translation of the word would be ‘ the silverfish of stones’. The grammatical gender of this genus is neuter following the opinion of ICZN (2018) for all genera derived from Lepisma.