Lactura basistriga (Barnes & McDunnough, 1913)

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 basistriga (Barnes & McDunnough, 1913) Figs 20, 28, 37, 49, 52, 61, 63, Table 1

Mieza basistriga Barnes and McDunnough, 1913: 142. Type locality: San Benito, Texas, USA. Type material: USNM

Diagnosis.

Lactura basistriga can be distinguished from L. rubritegula by the absence of dorsal red scales on the tegula. Most forms exhibit a basal, red, subcostal dash on the forewing, and all individuals lack the scattered flecking of red or brown scales characteristic of L. subfervens . Many, but not all individuals can be distinguished from L. rubritegula by a reduced upper postmedial spot and the convex arcing of the three lower postmedial spots, due to a more basal placement on the lowermost spot. Adults are exceedingly close to and often indistinguishable from those of L. nalli ; see comments under that species. With the exception of L. nalli and L. atrolinea , female genitalia differ from other Lactura in having four or five coils in ductus bursae. Larvae with a dark dorsum that ranges from smoky gray-green to nearly black, and without the metallic blue dorsal pinacula of L. atrolinea ; larvae of L. nalli are lime green above and lack any hint of white striping or black fill between the subdorsal stripes that are present in L. basistriga .

Description adult.

(Fig. 20) Forewing length: 9-11 mm (n = 97). Head. Shiny, white decumbent scales over vertex and frons. Labial palpi fuscous red, straight or slightly porrect. Antenna filiform, 0.6 length of forewing; shiny, white decumbent scales over scape and basal 1/3, transitioning to shiny, orange to fuscous orange scales; fuscous beneath. Thorax. Patagium mostly white; red basally, most apparent around perimeter of eye. Tegula white with small, ventral, red basal patch. Subtriangular, medial, mesothoracic red spot flanked posterolaterally by ellipsoid to bar-like red spots. Coxa and femur with reddish mesal surface, distal and ventral surfaces with admixture of both white and red scaling; tibia given more to white scaling; protarsus mostly red, meso- and metatarsus given to more white scaling. Forewing. Pearly white, with seven blood- to mahogany-red spots in oblique antemedial and postmedial series; without scattered dark scales (of L. subfervens ). Antemedial row with three spots; lower and upper spots often larger than middle spot; postmedial series with four spots: uppermost usually smaller or subequal to that below it; lower three forming straight line or, more commonly, a convex arc facing the termen. (These same three spots often form a concave arc open to termen in L. rubritegula due to a more distal placement of the lowermost spot.) Basal subcostal red dash from which the species derives its specific epithet, typically ending before the uppermost antemedial spot; subcostal dash always present in males, but its development (length and thickness varying among individuals); basal red subcostal dash frequently absent in females. Basal red scaling along costa narrows and ends before antemedial spots. Underside red with white fringe scales. Hindwing. Uniformly light orange-red above; light orange-red below, becoming paler along inner margin. Abdomen. Dorsum and sides brick red; venter rusty white. Two pairs of subventral intersegmental hairpencils (with 40-60 androconial scales) inserted between A6 and A7, and A7 and A8. Male Genitalia (Fig. 28) (n = 3). Male genitalic characters overlap with those of L. nalli and L. rubritegula . Female genitalia (Fig. 37) (n = 2). Papillae anales ca. 4 × longer than broad with dorsal sclerotized rim anastomosed with posterior apophyses. Ductus bursae with four or five coils, posterior half sublinear, transitioning to strongly coiled anterior half; diameter of coils increasing to corpus bursae, anteriormost coil 3 × greater in diameter than posteriormost coil (subequal to width of corpus bursae). Corpus bursae longer than broad; signa consisting of four, large hemispherical lobes with dentate interior projections; teeth widely spaced (similar to L. atrolinea ). Corpus bursae with anterior accessory pouch narrowed at its opening.

Description of living final instar.

(Fig. 49) Ground color glossy yellow, pale, or smoky green with variable black coloration over dorsum interrupted by wavy, white addorsal stripe. D2 seta borne from slightly elevated yellow wart connected by thick yellow to white subdorsal stripe; yellow warts less evident through midabdominal segments. Enlarged dorsal verrucae on A8 (bearing D1, D2, and SD1 setae), usually yellow or yellow-orange and black over mesal surface. Two pale, wavy supraspiracular stripes extending from T1-A8.

Distribution and biology.

Lactura basistriga inhabits the woodlands, thickets, palm forests, and scrublands of the lower Rio Grande Valley; presumably the core of its range is in Mexico. Breeding populations are known from the extreme southern Texas counties of Hidalgo and Cameron (Fig. 52). This species is sympatric with L. atrolinea in the United States; the moths are active at the same time of year and both feed on new foliage of saffron plum ( Sideroxylon celastrinum ). Peak activity is tied to early spring (March to May) and the fall rainy seasons (September into November) (Fig. 61).