Laricobius Rosenhauer, 1846

Leschen, Richard A. B., 2011, World review of Laricobius (Coleoptera: Derodontidae), Zootaxa 2908, pp. 1-44 : 3-4

Laricobius Rosenhauer, 1846

Type species by monotypy, L. erichsonii Rosenhauer

Description (based on Leschen and Beutel 2010). Total length 1.25–3.04 mm. Body elongate, dorsally slightly convex and ventrally flattened. Surface glabrous with vestiture of erect, suberect, or decumbent setae; foveae on head (between the antennal insertion and the eye, see Lawrence and Hlavac 1979), pronotum, and ventrites (figs 24–28), lacking tubercles or well-developed ridges; punctation consisting of large macropunctures dorsally (figs 22, 23, 31, 33) and smaller micropunctures dorsally and ventrally; surfaces with microsculpture (mostly apparent in dissections using compound microscope, see fig 33). Color variable. Head slightly declined and not srongly prognathous, not abruptly constricted to form a neck; temples, transverse occipital ridge and stridulatory files absent. Antennal insertions more or less exposed in dorsal view; antennal grooves absent. Compound eyes finely facetted; interfacetal setae present; two ocelli present (absent in some species). Mandible bidentate without well-developed mola and prostheca. Corporotentorium without median process. Prothorax quadrate to transverse. Pronotum with lateral carinae complete, weakly to strongly explanate, with or without a distinct bead and not dentate along entire margin. Procoxal cavities open. Protrochantin exposed with cavities strongly transverse and externally open, but narrowly so by acute hypomeral processes. Elytra with 10 punctate rows or striae, plus scutellary striole; suture not deflected at apex; epipleuron present in apical third (ending at level of metaventrite). Mesoventrite with paired procoxal rests (fig 24). Mesocoxae conical. Tibial apices with an apical comb of spines; tarsomeres 1–3 lobed below. Abdominal ventrites 1 and 2 connate (fig 28), lateral pores and canals present. Ovipositor short with short styli.

Comments. Species of Laricobius can be distinguished from other members of Derodontidae by the vestiture of long setae, lobed tarsomeres, open procoxal cavities, presence of a scutellary striole and 10 rows of punctures on the eyltra. A key to the genera is provided in Lawrence and Hlavac (1979).

A few characters in Leschen and Beutel (2010) require updating as follows. Ocelli, which are a diagnostic feature of Derodontidae , have recently been recorded as absent in a few species of Laricobius ( Montgomery et al. 2011; see also C10, below in cladistic analysis). Franz (1958b) referred to the ocelli of Laricobius as “dorsal lobes” because they did not have a sense organ visible in serial sections. True ocelli are confirmed by the innervation of the optic nerve with the ocellus which was been demonstrated by Leschen and Beutel (2004) for Derodontus LeConte. The mesoventrite has paired procoxal rests (not absent, as stated in Leschen and Beutel 2010). The ostium of the ejaculatory duct in the male genitalia of all derodontids is large and striate (figs 29, 30), and the distribution of this character in Coleoptera is unknown, though it does not appear in Cucujiformia which I have examined.

Cuticular features of adult derodontids and their potential function as chemical defense organs were discussed by Lawrence and Hlavac (1979). Laricobius has a range of cuticular features that include microsculpture (fig 33), micropunctures, macropunctures (figs 21–23, 31–33), and foveae (or pits; figs 24–27, 29). The difference between foveae and macropunctures is one of comparable size and depth of penetration of the integument and while micropunctures have a limited depth, I restrict the term foveae to those deeper invaginations at the four corners of the pronotum (seen more clearly in lateral view), on the ventrites and pleura, and the postantennal region of the head (see Lawrence and Hlavac 1979). Usually, these larger invaginations have white secretions, and in the postantennal fovea there are setae (see fig 6 of Lawrence and Hlavac 1979). The macropunctures of the elytra have been called “window punctures,” by Lawrence and Hlavac (1979) and these do not appear to have the annulation or multiple rings as seen in other foveae (compare figs 24 and 33). Franz (1958b) discussed the arrangement of the macropunctures (= pits) on the head of L. erichsonii and discovered that the number is variable and in remaining species these cephalic macropunctures may be connected by a weak to well-developed furrow, which may also vary within some species. By contrast, the foveature (number and position), though, is consistent among the material I have dissected.

Various characters are critical for the identification of Laricobius species, and these are presented in the diagnoses and keys for each species. Coloration of the body and appendages is useful and in the diagnoses and cladistic analysis I have referred to color value (light or pale versus dark) while in the descriptions the color is detailed. Elytral striae of Asian species without an explanate pronotum tend to have several macropunctures posteriorly confluent, especially in striae rows 1–4 and/or the punctures are contained within deep grooves. Stria 1 may also have punctures that are posteriorly confluent in species that have an explanate pronotum.

Detailed life history studies and descriptions of immature stages exist for two Laricobius species (i.e., Zilahi- Balogh et al. 2006) and like other members of the family ( Lawrence & Hlavac 1979; Crowson 1980; Lawrence 1982; Leschen & Beutel 2009), larvae and adults occur together in the same habitat. The foremost work on Laricobius biology and morphology was done by Franz (1958a, b) for L. erichsonii , and his studies should be consulted for a detailed account of the life history of this species. Predatory behavior of Laricobius is thought to be derived in the family ( Leschen 2000) from more primitive associations with fungi where the Holarctic genus Derodontus is found on homobasidiomycte fungi ( Lawrence & Hlavac 1979; Leschen 1994, 2002; Dodelin 2004) and the south temperate genus Nothoderodontus Crowson , sister taxon to Laricobius , is associated with sooty molds ( Lawrence 1985).

Larvae have been described and keyed by several authors (Franz 1958; Fukuda 1963, Lawrence & Hlavac 1979; Lawrence 1991; Lawrence et al. 1999b; Zilahi-Balogh et al. 2006).

The classification and phylogenetic relationships of Derodontidae , and within it, were summarized by Leschen and Beutel (2010). The family was removed from Bostrichiformia ( Lawrence & Newton 1995) and is now included in Derodontiformia Lawrence et al. (2010) along with Nosodendridae and Jacobsoniidae . Larval and adult morphology suggests that derodontids may be the sister taxon to Nosodendridae ( Beutel 1996; Ge et al. 2007), but this is an open question as phylogenetic results are mixed ( Caterino et al. 2002; Beutel & Leschen 2005; Ge et al. 2007; Hunt et al. 2007).

Though only four genera, there are three subfamilies in Derodontidae : Peltasticinae LeConte contains the single genus Peltastica Mannerheim , Derodontinae LeConte contains Derodontus , and Laricobiinae Mulsant & Rey contains Laricobius and Nothoderodontus . Relationships among the genera have been proposed by Crowson (1959, 1980), Fukuda (1963), and Lawrence & Hlavac (1979). Based on larval characters, Fukuda (1963) divided the family into the Laricobius and Derodontus groups, the latter consisting of Pelatistica and a clade comprising Derodontus and Nothoderodontus , largely in agreement with Crowson (1955, 1959; but see 1981). Lawrence & Hlavac (1979) placed Peltastica at the base of their two preferred trees, with uncertain relationships among Derodontus , Laricobius , and Nothoderodontus . In the recent cladistic analysis using adult and larval characters, Ge et al. (2007) showed that Peltastica is the sister taxon to the remaining Derodontidae .