Moths of North Carolina
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5 NC Records

Eriocraniella mediabulla Davis & Faeth, 1986 - No Common Name


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Taxonomy
Superfamily: Eriocranioidea Family: EriocraniidaeP3 Number: 70012.00 MONA Number: 13.10
Comments: Eriocraniella is a genus of primitive moths with eight described Nearctic species that specialize on oaks.
Identification
Field Guide Descriptions: Online Photographs: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLDTechnical Description, Adults: Davis and Faeth (1986).Technical Description, Immature Stages: Davis and Faeth (1986).                                                                                 
Adult Markings: Eriocraniella mediabulla is a small moth with shiny black to dark fuscous wings. The forewings are uniformly black with a distinct golden to sometimes bluish luster. The hindwings are slightly paler, and are fuscous with a purplish luster along the costal half (Davis and Faeth, 1986). The legs are rather uniformly fuscous without distinct markings or annulations. The head is sparsely covered with mostly white to light buff piliform scales. The antennae are black, about one-half the length of the forewings, and have 29-34 segments. The maxillary palpi are mostly fuscous and suffused with grayish white mesally. The apex has a relatively large lobe that bears four stout setae, along with two pairs of smaller, subapical lobes that each bear a single large seta. The labial palps are sparsely covered with grayish white scales and have a relatively dense brush of fuscous, piliform scales. The mature larvae are typically no more than 9 mm long and 1.5 mm wide (Davis and Faeth, 1986). The head of the larva is uniformly light brown to straw-colored, with darkly outlined frontal sutures. Dyseriocrania griseocapitella is similar, but has metallic golden wings that are uniformly peppered with iridescent bluish purple scales, as well as pronounced hair tufts on the head and thorax (these are less pronounced and lighter colored in E. mediabulla). Eriocraniella platyptera is also similar, but is a northern form that appears to be restricted to the northeastern US.
Forewing Length: 3.8-4.1 mm for males; 3.3-3.7 mm for females (Davis and Faeth, 1986).
Adult Structural Features: The following is based on Davis and Faeth's (1986) descriptions of the genitalia. Males: The uncus is shallowly bilobed and the lobes are rounded. The anal tube is completely membranous and there are no basal sclerites. Socii are present and consist of a single, relatively large seta. The caudal margin of the vinculum forms a short, rounded medial knob with a broad base. The anterior apophyses are relatively short and broad, ca. 0.3 the length of the undivided vinculum. The base of the aedoeagus is bulbous. The ventral phallic branch is slightly curved and stout, and is nearly the diameter of the dorsal branch. The base of the ventral branch is moderately swollen and the apex has a triangular lobe. Females: The apex of the ovipositor is broadly acute and the lateral edges are serrulate with 9-10 minute teeth. The bursa copulatrix is moderately long, and greatly exceeds the cephalic apices of the anterior apophyses. The walls of the corpus bursa are entirely membranous. The vaginal sclerite is darkly sclerotized, moderately long (greatest width ca. 0.33 the length) and depressed, and lacks a median keel. The specific epithet (mediabulla) of this species is derived from the Latin media (middle) and bulla (knob) in reference to the diagnostic midventral, knoblike process on the vinculum of the male.
Adult ID Requirements: Identifiable from good quality photos of unworn specimens.
Immatures and Development: Davis and Faeth's (1986) account of the larval life history is based on their observations of larvae that mined Water Oak (Quercus nigra). Females insert their eggs near the edge of expanding fresh leaves, and typically select an oviposition site on the distal half of the leaf. In Florida, the eggs are normally laid around mid-March and hatch in 7-10 days. The larva initially create a linear mine in the upper epidermis of the leaf along the leaf margin. The mine elongates in the direction of the leaf apex, and eventually expands into a full-depth, blotch mine. The blotch is usually formed near the tip of the leaf, but can sometimes be farther back. Frass is deposited in semicircles within the blotch mine and often has a thread-like consistency. A larva completes development within 7-10 days, then cuts a crescent-shaped hole in the lower leaf surface, drops to the ground, and burrows into the soil and spins a cocoon. The insect remains in the soil until the following spring. Little is known about the pupal stage, except that pupation occurs in the soil. Other eriocraniids on oak are known to pupate only after several months or more of larval diapause in the soil, so it is likely that E. mediabulla does the same. The adults emerge the following spring as the trees break winter dormancy. In Florida, ants (Crematogaster ashmeadi; Pseudomyrmex ejectus) often chew through the soft leaves and remove larvae from the mines. Ant predation can be a major cause of larval mortality (Faeth, 1980). The most diagnostic features of the larva are the absence of the cranial setae 01 and Al, and the presence of an entire complement of 10 primary setae on the ninth abdominal segment (Davis and Faeth, 1986). This species is the only eriocraniid known to have lost 01. Davis and Faeth (1986) noted that many eriocraniids develop an oval hole where the egg is laid on the leaf. Florida specimens of E. mediabulla that they examined typically lacked the hole. In contrast, mines from North Carolina that were verified by rearing the adults typically had the hole. Thus, the presence or absence of a hole at the egg deposition site appears to vary geographically.
Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants.
Distribution in North Carolina
Distribution: Eriocraniella mediabulla is primarily found in the Coastal Plain from eastern Texas to Florida, Georgia, and extreme southern North Carolina. As of 2020, our two county records are the northernmost records for this species.
County Map: Clicking on a county returns the records for the species in that county.
Flight Dates:
 High Mountains (HM) ≥ 4,000 ft.
 Low Mountains (LM) < 4,000 ft.
 Piedmont (Pd)
 Coastal Plain (CP)

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