Moths of North Carolina
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View PDFEriocraniidae Members: 2 NC Records

Eriocraniella mediabulla Davis & Faeth, 1986 - No Common Name


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; BugGuideTechnical 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 palpi 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).
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 further back. Frass is deposited in semicircles within the blotch mine. 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.
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)

Click on graph to enlarge
Immature Dates:
 High Mountains (HM) ≥ 4,000 ft.
 Low Mountains (LM) < 4,000 ft.
 Piedmont (Pd)
 Coastal Plain (CP)

Click on graph to enlarge
Flight Comments: Adults are active from early March to mid April. Local populations are univoltine, as is the case for all other members of the Eriocraniidae.
Habitats and Life History
Habitats: Populations are found in coastal hardwood forests with oaks. Populations in Florida appear to rely primary on Quercus nigra, which is associated with bottomland forests. One of our NC records is from a xeric upland habitat with Q. laevis, suggesting that this species may also frequent Xeric-Mesic, Sandy Woodlands and Scrub habitat. Additional records are needed for North Carolina to determine the full range of habitats used by this species within the state.
Larval Host Plants: Eriocraniella mediabulla has been reared from Water Oak (Quercus nigra), and the mines have been found on Sand Laurel Oak (Q. hemisphaerica), Southern Red Oak (Q. falcata), White Oak (Q. alba) and Live Oak (Q. virginiana) in northern Florida. Our one record for North Carolina is based on mines on Turkey Oak (Q. laevis).
Observation Methods: This species appears to be at the northern edge of its range in North Carolina. Searching for active mines may be the best way to document populations, but rearing is challenging since the adults require almost a year to develop after the larvae enter soil. The mines of E. mediabulla are generally similar to those of Dyseriocrania griseocapitella, which is the only other sympatric species of Eriocraniidae. Both have an initial linear portion that abruptly broadens to form a large blotch. However, the initial linear portion of a D. griseocapitella mine is usually obliterated by the blotch, which eventually causing a fissure to form in the leaf (Eiseman, 2019). The linear portion remains intact in E. mediabulla mines, and a fissure does not form. Another difference between the mines is that a small, oval hole normally develops around the egg scar of D. griseocapitella as the leaf expands. This hole is usually not evident on E. mediabulla mines (Davis and Faeth, 1986).
Wikipedia
Status in North Carolina
Natural Heritage Program Status:
Natural Heritage Program Ranks: GNR S2S4
State Protection:
Comments: Eriocraniella mediabulla was previously known to occur no further north than Florida and Georgia, which suggest that our North Carolina populations may be disjunct from the main range to the south.

 Photo Gallery for Eriocraniella mediabulla - No common name

Photos: 4

Recorded by: Mark Shields on 2020-03-28
Onslow Co.
Comment:
Recorded by: Tracy S. Feldman on 2016-04-20
Scotland Co.
Comment: A leaf mine on Quercus laevis that was in a remnant longleaf pine habitat along a swamp (see companion photo of the adult that emerged).
Recorded by: Tracy S. Feldman on 2016-04-20
Scotland Co.
Comment: A leaf mine on Quercus laevis that was in a remnant longleaf pine habitat along a swamp (see companion photo of the adult that emerged).
Recorded by: Tracy S. Feldman on 2016-04-20
Scotland Co.
Comment: Reared by Tracy Feldman and Charley Eiseman on Quercus laevis in a remnant longleaf pine habitat along a swamp. The adult emerged the following spring, on 10 April 2017, and was identified by Terry Harrison. Photo by Charley Eiseman.