Mesosemia walteri Brévignon, 1998

Nielsen, Gregory J. & Kaminski, Lucas A., 2018, Immature stages of the Rubiaceae-feeding metalmark butterflies (Lepidoptera: Riodinidae), and a new function for the tentacle nectary organs, Zootaxa 4524 (1), pp. 1-32 : 13-18

Mesosemia walteri Brévignon, 1998

Natural history. An infrequent visitor to the study site with most records from the first half of the rainy season.

Males were observed perching during the late morning hours low to the ground at a height of 30 to 40 cm. They shared part of a perching site with M. cippus and frequented the more shady areas. Three eggs were encountered by chance, all scattered on the underside of a single leaf along with an egg clutch of M. cippus . Before that discovery, only three larvae had been found during 4 years. Larval development time was 23–26 days. TNOs were everted and liquid produced by a fifth instar larva after contact by an ant ( Fig. 90 ). The prepupal stage lasted three days as the larvae wandered the food plant, eventually settling at a leaf node to spin the pupal attachment site. Adults emerged in the morning between 10–12 h (n = 3). Eggs and larvae were found on Ps. caerulea and Pa. racemosa (Rubiaceae) .

Description of immature stages. Egg ( Fig. 83 ). Eggs hatched after 6 days but total embryonic development time unknown Diameter 0.47–0.49 mm, height 0.32 mm (n = 4). Color bright yellow, exochorion with irregular rows of approximately 15 varying sized hexagon shapes from the micropyle to the base. Micropyle area concave.

First instar ( Fig. 84 ). Duration 3–4 days. Head capsule width 0.27– 0.29 mm (n = 7), color translucent tan, ocelli black. Length upon eclosion 1.2 mm, maximum length 1.8 mm. Body yellowish with one pair of primary setae on dorsal of each segment.

Second instar ( Fig. 85 ). Duration 4 days. Head capsule width 0.43–0.48 mm (n = 5). Maximum length 2.9–3.2 mm (n = 6). Head light tan, body light green.

Third instar ( Fig. 86 ). Duration 4 days. Head capsule width 0.66–0.71 mm (n = 3). Initial length 3.5 mm, maximum body length 6.7 mm (n = 3). Head capsule translucent light green: ocelli black. Body pale green with a darker green dorsal. A pair of white spots with a connecting bar on the posterior edge of segments T3 to A6. TNOs on A8 translucent, paler than background.

Fourth instar ( Fig. 87 ). Duration 5 days. Head capsule width 0.95–1.0 mm (n = 6), color green and tan. Body length from 6.9 after molting to 10.6 mm. Overall body color medium green with a darker green dorsal area. A pair of dorsolateral white spots on the anterior edge of segments T2 through A7. Small white setae scattered over the upper body surface. Dorsal setae arise from a pair of verrucae on the thoracic segments and from 2 pairs on the abdominal segments. Largest setae are translucent light brown, the remainder dark, near black. Lateral setae long, white. Spiracles white. TNOs on A8 large and translucent, when completely contracted are the same color as the body.

Fifth (last) instar ( Figs. 88–91 ). Duration 5–7 days. Head capsule width 1.64-1.67 mm (n = 3). Body length from 11.5–20.4 mm. Head green. Body medium green with the lateral areas slightly paler. A pair of dorsolateral white spots on the posterior edge of segments T2–A8 with a white connecting bar on the posterior edge of A1–A5. Dorsal setae dark reddish-brown born by two pairs of oval shaped paired verrucae on each abdominal segment. Each verruca bore four varying size setae ( Fig. 89 ). The dark dorsal setae numbered 20 on each segment. Each lateral lobe had numerous medium length white setae that project downward and interlace with the setae on the conjoining segments. TNOs observed to evert after contact by an ant. Spiracles white; the diameter of the spiracles on A8 twice the diameter of the anterior spiracles. The prepupal larvae ( Fig. 91 ) developed numerous white spots and the anterior, posterior and lateral lobes of each segment turned a reddish brown. Just before molting the larvae turned green again.

Pupa ( Fig. 92 ). Duration 12–13 days (n = 3). Maximum length 12–13.7 mm, width at A2 = 3.7 mm (n = 6). Pronotum and center of the T2 thoracic domed and last abdominal segments whitish-tan. Lateral edges of thorax and abdominal segments green. Crest on segment A2 whitish-tan. Spine-like seta project from the anterior edge of the head, eyes and the posterior edges of the abdominal segments and slightly shorter setae present over the upper body surface. Eyes setose. The silk girdle crossed the anterior of segment A2.

Figures

FIGURES 83–92. Immature stages of Mesosemia walteri. 83, egg; 84, first instar; 85 first (above) and second instar (below); 86, third instar in dorsal view; 87, fourth instar in dorsal view; 88, last instar in lateral view; 89, detail of abdominal tegument in dorsal view showing dorsal setae on verrucae; 90, last instar dorsal view, note the TNOs everted (arrow); 91, prepupa in lateral view; 92 pupa in dorsal (left) and lateral (right) views.