Lactura Walker, 1854: 485

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 Walker, 1854: 485 Figs 1-2, 3, 4, 5, 6, 7, 8, 9-14, 50-51, 52-53, 63, Table 1

Type-species.

Lactura dives Walker, 1854: 485.

Heppner (1997) successfully applied to conserve the widely used name Lactura Walker, 1854 and suppress the generic names Eustixis Hübner, [1827-31] and Mieza Walker, 1854 ( ICZN 1999). Heppner’s justification is discussed below, in the treatment for Lactura pupula . Generic synonyms can be found in Nye and Fletcher (1991) and Heppner (1995).

Generic description for adult Nearctic Lactura .

Medium-sized (wingspan 17-26 mm) with respect to other members of the family. Body salmon red. Head. Antenna filiform in both sexes; labial palpus porrect, maxillary palpus small. Thorax. Adult forewing elongate and subquadrangular, widest at 2/3, and typically satin white or white with speckled brown or red maculation. Oblique antemedial and postmedial rows of red or black spots often present. Apex broadly rounded and little differentiated from outer margin, bounded within R4 and R5; likewise, tornus poorly differentiated. Forewing discal cell with areole; R, M, and Cu veins sessile; CuA veins running to tornus; A1 and A2 fused from basal quarter to inner margin; A3 absent. Hindwing oval quadrate and uniformly pink-red or red-orange with elongate fringe scales. Frenulum 1/5 the size of hindwing length; wing apex poorly defined, bounded within Rs and M1; R, M, and Cu veins sessile; vannal area greatly enlarged; distinct fold between A1+A2 and A3. Venation as in Fig. 3. Tibial spur formula 0 –2– 4. Abdomen. Orange-red, midventer paler, often rusty white. One to two sets of androconial hairpencils within intersegmental folds between A7 and A8 ( L. pupula , some L. subfervens ), or A6 and A7 and A7 and A8 ( L. atrolinea , L. basistriga , L. nalli , L. rubritegula , some L. subfervens ). Cluster of elliptic scales anterior to spiracle and dorsad of hairpencil. At rest, the hairpencil overlays this scale cluster (presumably loading pheromone onto the hairpencil). Male genitalia (Figs 23-30). Uncus narrow, strongly down-curved and cylindrical, ending in apical spine. Tegumen pulmonate with strong medial crease. Valva elongate-oval (2.0-2.5 × longer than wide); costa covered in long setae, concave at distal third with broadly rounded apex; outer margin with shorter, thicker scales; lateral lobe of juxta with spiniform setae (more sclerotized and robust with thicker setae in L. subfervens , L. basistriga , and L. rubritegula ). Vinculum narrow, U-shaped, subquadrangular. Aedeagus exceeding length of valva (~4.5 × longer than wide) with broadly rounded base and gaping concave aperture at apex. Aperture oblique in L. subfervens , L. basistriga , L. nalli , and L. rubritegula . Apical thumb-like process present in L. pupula and L. atrolinea . Female genitalia (Figs 37-43). Papillae anales ca. 4 × times longer than broad with dorsal sclerotized rim conjoined with posterior apophyses. Apophyses rod-like; posterior apophysis ca. three times longer than anterior apophysis. Antrum modestly differentiated, weakly sclerotized, hat-shaped to quadrangular. Ductus bursae distally linear and then variously drawn into series of coils (the number of which is species specific), without accessory diverticula; diameter gradually increasing to corpus bursae and coils becoming more closely drawn together anteriorly. Ductus seminalis attached proximate to antrum. Corpus bursae longer than broad with signa arranged in four hemispherical lobes with dentate interior projections. Signa positioned in two transverse groups; posterior signa half again the size of anterior signa. Accessory pouch sometimes present at anterior end of corpus bursae ( L. atrolinea , L. basistriga , L. nalli ).

Color and habitus of living final instar larva

(Figs 44-49). Caterpillar shiny, usually brightly colored, somewhat tacky to the touch, and resembling small limacodids but with short, crochet-bearing prolegs and greater degree of translucence. Ground color green, with brown, black, or green dorsum. Dorsal and subdorsal setae borne from yellow, orange, black, and in some cases blue ( L. atrolinea ) translucent warts. Prothoracic plate well differentiated, divided medially; head partially retracted into thorax. Head dark brown or black, strongly sclerotized with long antennae.

Final instar larva

(Figs 7, 8). Description based on L. pupula . Head. Somewhat prognathous; anterior half more strongly sclerotized; darkly melanized patches to either side and through frons; larger patch, that includes stemmata, extending to level of P1 seta; labrum (0.2 mm long x 0.4 mm wide) with margins rounded and a medial notch; clypeus bulging; antenna longer than labial palpus; head setae generally short except for anteriormost seta of AF, A, S, and SS groups. Thorax (Fig. 7). T1: Prothoracic shield well developed and strongly sclerotized along mesal and posterior edges; XD1, XD2, SD1, and D2 longest setae on prothorax; D1 and D2 shifted near anterior edge of pronotum, D2 nearly twice as long as D1 and arising midway between and just posteriad of XD1 and XD2; MXD1 included on prothoracic shield directly posterior to D2. Three pits on prothoracic shield; uppermost posteriad of XD1, and two closely set pits dorsad of SD2. Prothoracic spiracle ovate, diameter 0.3 × larger than anterior abdominal spiracles. L group trisetose on raised fleshy wart ventroanteriad to spiracle; two SV setae aligned horizontally, each borne from fleshy wart. T2: All setae borne from raised fleshy warts that become increasingly sclerotized to point where seta issues, with size of wart and degree of sclerotization decreasing ventrad. D1, D2, and SD2 nearly in line; D1 and D2 subequal in length and sharing common ridge; SD1 and SD2 also sharing common ridge. Two dorsal L setae sharing a common fleshy wart and lower L seta positioned midway between upper L setae and SV setae. SV1 and SV2 on shared lateral swelling. T3: As in T2 except with only two L setae; uppermost L seta shifted upward and sharing protuberance with SD setae. Abdomen (Figs 7, 8). First eight segments with elliptical subspiracular gland and smaller subventral swelling (that may also be glandular). Setae mostly aligned along spiracular meridian and borne from clear, raised, wart-like fleshy swellings. A1: D1 and D2 on common swelling, transversely aligned with SD1 and spiracle; SD1 above spiracle; SD2 not observed (presumably microscopic); spiracle circular. L1 and L2 on same swelling below subspiracular gland; L2 (evidently) two-thirds length of L1 and located dorsoposteriad; L3 paired on separate swelling; SV1, SV2, and V1 in line, SV2 less than half size of SV1; V1 seta directed mesad. A2: Same as A1. A3-A6: D1, D2, SD1, L1, and L2 as on A1 and A2. L3 setae horizontally positioned beneath subventral swelling. Proleg with SV and V setae; 32-35 crochets in biordinal, mesal semi-circle along inner and posterior margin. A7: As in previous segments. SD1 dorsoposteriad to spiracle. V1 reduced or concealed in fold of subventral swelling. A8: D2 posteriolaterad to D1; both lightly sclerotized; spiracle nearly circular, 0.12 mm in diameter; 3 L setae. A9: D2 anterior to D1; D1, D2, and SD2 on enlarged wart; D1 pinaculum sclerotized; single L seta. A10: modestly sclerotized; four pairs of setae along caudal margin; 28-30 crochets; anal plate with melanized patch to either side of midline.

Pupa

(Figs 5, 6, 14). Subobtect, broadest through abdominal segments and modestly dorsoventrally flattened; antennae, legs, and wings loosely fused to body; setae very short and inconspicuous. Labial palpi visible; proboscis ending beyond protibia; caudal margin of metathorax curved upward and forming low ridge over dorsum of first abdominal tergite. Forewing apex distinctly falcate; hindwing exposed with vannal lobe extended upward toward spiracles. Pro-, meso-, and metatarsus fully visible; mesotibia ending between anterior of A5 to caudal margin of A7; metatibia and antenna subequal, and of variable length, extending to caudal margin of A7 to exceeding A10. Abdomen swollen through spiracular and subspiracular areas (perhaps as a consequence of larval subspiracular glands and subventral swellings); A2-A8 with supraspiracular recess and narrow band of rearward-directed teeth along anterior margin extending from midline nearly to supraspiracular area (presumably assisting in eclosion). A10 smooth with slight cleft and posterolateral protrusions; cocoon cutter, cremaster, and pseudocremaster absent.

Cocoon

(Fig. 13). Parchment-like, upper 4/5 of cocoon thick, tough, and carapace-like. Outer edge of cocoon with darkly stained, irregular, reticulate skirt which serves to anchor cocoon to substrate. Floor of cocoon tan, parchment-like; U-shaped operculum at one end tears free at eclosion. Pupa not extruded at eclosion.

Distribution and biology

(Figs 9-14, 50-53). North American Lactura are found in woodlands, scrublands, and thicket communities from Kansas, Missouri, Illinois, and Kentucky, south through Texas and the Gulf States, east to coastal South Carolina, Georgia, and the whole of Florida, continuing into the Caribbean and Mexico (Figs 52, 53). All species treated here feed exclusively on Sideroxylon spp. ( Sapotaceae ) and overwinter as prepupae inside a tough reddish to brownish cocoon spun in leaf litter (Fig. 13). Across much of their range in the United States, Lactura are primarily univoltine, tied to new growth as larvae. Species of the Rio Grande Valley and southern Florida occur nearly year-round, at least in small numbers, if new leaves are present. In captivity larvae typically feed from leaf undersides, with the head partially retracted into the prothorax. The fecal pellets are characteristically spherical, lacking any hint of the concave depression common to the pellets of limacodids and megalopygids.

Lactura are difficult to rear, often molding or desiccating as prepupae. We have had modest success rearing larvae in vials with a deep (3-5 cm), occasionally moistened, layer of peat or coir.

Larvae secrete a tacky exudate from their integument to which feculae adhere and often remain attached until the next molt. We suspect the exudate is a deterrent to ants and other invertebrates, as such sticky secretions have been shown to be in the caterpillars of the related Dalceridae ( Epstein et al. 1994). When Lactura caterpillars are threatened, they evert transparent, balloon-like vesicles from the side of their body (Figs 50, 51) that secrete a sticky, mucilaginous fluid. As far as known, these structures are present in all Nearctic species, but especially apparent in L. pupula . It is unclear how prevalent these subspiracular glands and associated behaviors are among other lacturids because the life histories for most species remain unknown.

We suspect adult Lactura sometimes disperse from their natal colonies, given that several collection records appear to be out of range, e.g., a single L. rubritegula from Houston, Texas (Fig. 52) ( Matson and Wagner 2017). Individuals have also been taken or photographed outside the range of their respective Sideroxylon hosts. Adults have a well-developed proboscis, but we have no records of adults feeding at flowers. Despite their bright, seemingly aposematic coloration, the adults of Nearctic species are thought to be exclusively nocturnal.