Socoroma leafminer (Cremastobombycia socoromaensis) from Chile with larvae mining leaves Baccharis tola

NEWS - Socoroma leafminer (Cremastobombycia socoromaensis Vargas sp. nov. Lepidoptera, Gracillariidae, Lithocolletinae) from the dry highlands of the western slopes of the Andes in northern Chile with larvae mining leaves on the shrub Baccharis tola Phil. (Asteraceae) is the first record of Cremastobombycia Braun 1908 in South America.

No Cremastobombycia species have been reported from South America. However, morphological examination revealed that a micromoth obtained from a leafminer collected in the arid Andean highlands of northern Chile was an undescribed species in this genus.

C. socoromaensis was recognized based on wing pattern and genital morphology. The forewings of the male (3.6–3.7 mm long) are orange-brown and have indistinct creamy white markings: a short longitudinal subbasal line and three costal strigulae and two dorsal oblique strigulae.

Although the female forewings (3.0–3.1 mm long) are also orange-brown with subbasal lines similar to those of the male, the four distinct creamy white transverse fasciae and three distinct dark brown spots are distinct from the pattern of the male forewings.

The male genitalia resemble Cremastobombycia chromolaenae Davis 2013 from Florida, USA. However, the indistinct longitudinal subbasal lines on the first forewing contrast sharply with the prominent white longitudinal lines along the basal third of the second forewing.

Furthermore, the posterior projection of the tegument, the straight margin between the transtillar lobes, the vesica with a cornus on the male genitalia, and the diamond-shaped signum with transverse folds on the female genitalia allow for the recognition of C. socoromaensis; like the male genitalia the tegument lacks posterior projections, the margin between the transtillar lobes is concave, and the vesica lacks a cornus, and the female genitalia have a strongly bilobed signum.

The transverse folds of the signum in the female genitalia resemble those of Cremastobombycia lantanella (De Prins, 2019). However, in contrast to the male genitalia in C. socoromaensis, the genitalia of C. lantanella lack a posterior projection of the tegument, have a sac shorter than the width of the vinculum, and lack a cornus on the vesica.

The currently documented range of C. socoromaensis is restricted to the type site around the village of Socoroma at 3400 m elevation on the western slope of the Andes in the Parinacota Province of northern Chile. B. tola is the only host plant currently recorded. In northern Chile, B. tola inhabits the Andean highlands at elevations of 2000-4800 m.

C. socoromaensis eggs are laid individually mainly on the adaxial surface of leaves. Larvae and pupae are endophytic. The development of the hypermetamorphic larva includes an early sap-feeding form and a later tissue-feeding form. The elongated, prominent adult branch occupies most of the leaf.

The last instar tissue-feeding larva constructs a loose, smooth, cylindrical silk cocoon to pupate in which it attaches to the mine by its anterior and posterior ends. The cocoon and the mine surface are pierced by the frontal processes of the pupa to allow the adult to emerge.

DESCRIPTION

Male. Head. Vertex with narrow, elongate, raised scales, mostly brownish-orange and a few dark brown; frons with narrow, elongate, smooth brownish-orange scales. Antenna filiform, slightly shorter than forewing, silvery-gray, scape with pecten. Labial palpus straight, drooping, silvery-gray.

Thorax (forewing length 3.6–3.7 mm). Mostly brownish-orange with scattered creamy-white dorsally; silvery-gray ventrally; legs silvery-gray. Forewing brownish-orange with poorly defined creamy-white markings, including a short longitudinal sub-basal streak and three costal and two dorsal oblique strigulae; first two costal strigulae arising before the middle, third one arising near the apex; dorsal strigulae arising near the middle; scattered dark brown scales between the two dorsal strigulae and between the second dorsal and the third costal strigulae; fringe brownish-orange. Hindwing uniformly gray with gray fringe.

Abdomen. Mostly gray with scattered creamy-white scales; sternum VIII flap-like, elongate.

Male genitalia. Tegumen with narrow arms slightly widened on dorsal half, with flat, somewhat triangular posterior projection bearing eight elongate setae near apex. Vinculum U-shaped. Saccus a narrow, elongate, slightly sinuous rod. Subscaphium a narrow, poorly sclerotized longitudinal stripe ending in a broad patch of microtrichiae. Juxta a broad, poorly sclerotized plate joined to posterior margin of vinculum by a narrow stripe. Transtilla well-differentiated with two widely separated lobes on anterior margin. Valva elongate, slender, length about 1.5 times the saccus; dorsal margin slightly convex near tip; ventral margin mostly straight; apex widely rounded; median surface with dense patch of stout setae on distal third. Phallus cylindrical, straight, about twice the saccus length; coecum about a third the phallus length; a narrow cleft on distal third with two small spine-like projections on opposed margins; vesica with a narrow, elongate cornutus; ductus ejaculatorius with a ring-shaped sclerite near the tip of the coecum.

Female. Mostly similar to male, except for forewing length (3.0–3.1 mm) and maculation pattern; mostly brownish-orange with a poorly defined, short creamy-white longitudinal sub-basal streak and four well-defined creamy-white transverse fasciae, the first one convex, the three other straight; a small dark brown spot on the middle of the outer margin of the first fascia; a great dark brown spot between the outer margin of the second and the inner margin of the third fasciae and between the outer margin of the third and the inner margin of the fourth fasciae; a small dark brown spot on the outer margin of the fourth fascia.

Female genitalia. Papillae anales flattened, bearing long setae mostly near posterior margin. Posterior apophyses straight, slightly longer than posterior margin of papillae anales. Anterior apophyses dorsally curved, length similar to posterior apophyses. Ostium near the posterior margin of sternum VII. Ductus bursae membranous, narrow, about three times the posterior apophyses length; ductus seminalis arising near the posterior third of ductus bursae. Corpus bursae membranous, oval, about half the length of ductus bursae; signum a slightly sclerotized diamond-shaped plate on posterior half of corpus bursae with a well-sclerotized semicircular serrated transverse fold near the middle.

Original research

Vargas HA (2024). Cremastobombycia socoromaensis sp. nov., the first South American representative of the micromoth genus Cremastobombycia Braun (Lepidoptera, Gracillariidae, Lithocolletinae). ZooKeys 1218: 333-342, DOI:10.3897/zookeys.1218.135606

Dlium theDlium