Lactura subfervens Walker

Matson, Tanner A., Wagner, David L. & Miller, Scott E., 2019, A Revision of North American Lactura (Lepidoptera, Zygaenoidea, Lacturidae), ZooKeys 846, pp. 75-116 : 75

Lactura subfervens Walker Figs 15-17, 24, 27, 33, 36, 42-43, 45, 53, 58, 59, 63, Table 1

Mieza subfervens Walker 1854: 527. Type locality: Texas, USA. Type material: NHMUK, TYPE - BMNH(E) 819792

Lactura psammitis , Zeller 1872: 562; syn. n. Type locality: Texas, USA. Type material: NHMUK, TYPE - BMNH(E) 1377410

Lactura rhodocentra , Meyrick 1913: 142; syn. n. Type Locality: Texas, USA. Type material: not found at NHMUK

Notes.

Zeller described Enaemia psammitis from Texas in 1872. As early as 1874, Grote synonymized L. psammitis with L. subfervens ; a decision followed subsequently by Barnes and McDunnough (1913, 1917). Heppner and Duckworth (1983) gave L. psammitis species status in their checklist without explanation. Perhaps, L. psammitis has persisted because phenotypes of L. subfervens , mostly from Oklahoma and Texas, with reduced forewing speckling were thought to represent a species independent from L. subfervens . Based on extensive barcode and phylogenetic data, multiple larval collections, and genitalic dissections, we see no evidence to suggest L. psammitis is a valid species. The original description of L. psammitis and type specimen in the NHMUK agree in detail with forms of L. subfervens , so we follow others and return the name to synonymy.

Lactura rhodocentra ( Mieza rhodocentra ) was described from Texas by Meyrick in 1913. Shortly thereafter, it was designated as a synonym of L. basistriga by Barnes and McDunnough (1917) without explanation. Meyrick’s description which mentions "with a few scattered red [forewing] scales," unambiguously places it as a form of L. subfervens . While the type of L. rhodocentra cannot be located at the Natural History Museum in London, we are not convinced that it no longer exists, because there are random pockets of Meyrick specimens spread throughout the large accumulation of “accessions” of unsorted microlepidoptera. Clarke (1955) did not include a depository for this species, suggesting the type was not present at the NHMUK at that time. Furthermore, it is unlikely that Meyrick would have had access to specimens of L. basistriga , L. nalli , or L. rubritegula , given that all three are geographically restricted to south Texas, and distant from major population centers or travel routes of the early 1900s. We have collected Lactura larvae and adults from various locales in eastern Texas, the likely source of the types for both names, examined the Lactura collections of Texas A&M University and the private collections of the late Edward Knudson (Houston) and James McDermott (Dallas area), checked barcodes for all US specimens, and see no evidence for the existence of a species that differs from the six treated species in this work. Like L. psammitis , we regard this name to be a synonym of Lactura subfervens .

Diagnosis.

Lactura subfervens adults can be immediately distinguished by the presence of scattered smoky red scales (although highly variable in density) over the forewing. The forewing lacks the basal subcostal red or black dash usually present in L. atrolinea , L. basistriga , and L. nalli . This species can also be separated from L. basistriga , L. nalli , and L. rubritegula by the absence of red scaling at the base of the patagium. Female genitalia differ from those of other Lactura in having 11 or 12 coils along the ductus bursae. The caterpillar is among the most distinct of the North America Lactura : it is the only species whose ground color is predominately white; seven pairs of pale stripes run the length of the body, giving the larva a frosted appearance. The darker stripes are due to the larva’s internal coloration showing through its transparent body wall; with the exception of the prothoracic shield, there is essentially no black pigmentation dorsally or laterally along the trunk.

Description adult

(Figs 15-17). Forewing length: 9-13 mm (n = 495). Head. Shiny, white decumbent scales over vertex and frons. Labial palpus slightly porrect to straight, brick red, subequal to diameter of eye. Antenna filiform, 2/3 length of forewing; shiny, white above, fuscous below. Thorax. Predominantly white. Patagium white; tegula with conspicuous basal band of red scales, similar to L. rubritegula . Medial mesothoracic red spot flanked posterolaterally by red ellipsoid to bar-like spots. Coxae, femora, and tibiae with red dorsal surface, and white or admixture of white- and red-scaled ventral surface; tarsi fuscous to red. Forewing. Mostly white, variable. Typically with seven crimson- to russet-red spots in antemedial and postmedial oblique series. Spotting sometimes reduced, but generally antemedial series with three spots and postmedial series with four spots. Varying degrees of scattered red to brown scales throughout. Some individuals with speckling so thick as to obscure antemedial and postmedial spots; other forms with only a few red or fuscous scales. Basal red scaling along costa narrows and then ends before antemedial spots. Fringe scales usually matching white forewing, although some individuals with red fringe. Underside light red with matching or slightly paler fringe scales. Hindwing. Uniformly light red above and below. Abdomen. Dorsum and sides brick red; venter rusty white. Ventral intersegmental hairpencils (with 40-60 androconial scales) inserted between A7 and A8. A second set of brushes between A6 and A7 was found in three preparations (Figs 33, 36). Male Genitalia (Figs 24, 27) (n = 6). Uncus strongly down-curved; medially constricted in basal third; distal part cylindrical and tapered (usually longer than congeners), terminating in reduced thorn-like apical spine. Valva elongate-oval, 2.5 × longer than wide, costa slightly concave along distal third; apex broadly rounded; lateral lobe of juxta with 15-20+ thickened spiniform setae. Vinculum narrow, U-shaped, subquadrangular. Aedeagus cylindrical, exceeding length of valva; base broadly rounded, gradually narrowing to apex; apex with concave oblique aperture; subapical thumb-like process absent. Female genitalia (Figs 42, 43) (n = 3). Papillae anales ca. 4 × longer than broad with dorsal sclerotized rim fused with posterior apophyses. Ductus bursae with 11 or 12 coils, posterior two coils more open; coil diameters more or less uniform with anteriormost coil slightly larger than others. Corpus bursae longer than broad with quadrate signa reduced; arms fused; lightly sclerotized in one preparation (USNM 76686). Corpus bursae without anterior accessory pouch.

Description of living final instar

(Fig. 45). Appearing frosty or pale green or exceptionally yellowish; seven pairs of whitish stripes run length of body; without black pigment dorsally or laterally. D2 on elevated yellow verrucae connected by thick yellow to white subdorsal stripe. Prothoracic shield well differentiated, medially divided, with much less black dorsal pigmentation relative to congeners. Head brown, partially retracted into prothorax.

Distribution and biology.

Lactura subfervens is found in woodlands, bottomlands, and thickets of central Texas northward to southeast Kansas, Missouri, and Illinois, and east through Gulf States to coastal Georgia (Fig. 53). Its range is largely sympatric with L. pupula , with both species mirroring the distribution of one of their shared host plants, Sideroxylon lanuginosum . Lactura subfervens is not found in southern Florida, unlike L. pupula . The species is essentially univoltine, typically flying very early in season (January to April) (Figs 58, 59), when Sideroxylon is producing new leaves, although there are smaller, facultative broods across the southern portions of its range, with captures into June and occasionally into the fall. We suspect that larvae from these adults commonly fail due to lack of appropriate foliage. From at least the Dallas area west into the Hill Country region of Texas, L. subfervens can reach larval densities high enough to severely damage or completely defoliate Sideroxylon lanuginosum .

Remarks.

For decades, less speckled forms of L. subfervens have been misidentified as L. basistriga in collections, literature ( Heppner 2003), and on commonly used internet sites, e.g., BugGuide, iNaturalist, and Moth Photographers Group. Much of this confusion was avoidable and speaks to the merit (and necessity) of revisiting original descriptions and examining types. Barnes and McDunnough’s (1913) original description of L. basistriga provides clear diagnostic characters that unambiguously distinguished the adult from L. subfervens : "lacking the brown streaks on the forewings and in having a red basal streak below the costa," although the latter character is sometimes absent.