Moths of North Carolina
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4 NC Records

Pediasia trisecta (Walker, 1856) - Sod Webworm Moth

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Taxonomy
Superfamily: Pyraloidea Family: CrambidaeSubfamily: CrambinaeTribe: CrambiniP3 Number: 80a1522 MONA Number: 5413.00
Identification
Field Guide Descriptions: Covell (1984); Beadle and Leckie (2012)Online Resources: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLDTechnical Description, Adults: Forbes (1923)Technical Description, Immature Stages: Ainslie (1927)                                                                                 
Adult Markings: The following description is mostly based on that of Fernald (1896) and Forbes (1923). The palps are light tan with a mix of fuscous or grayish scales on the outside. The head and thorax are light yellowish-tan with varying levels of gray shading. The forewing ground color is pale yellowish-tan and shaded with dull gray between the veins, leaving fine pale streaks on the veins. The gray shading is often absent or faint in the costal half of the wing to about one-half to two-thirds the wing length. The median and subterminal lines are poorly developed and often represented by blackish oblique shades across the middle of the wing. The terminal line is either missing or represented by a few weak dots that are often obsolete. The fringe is fuscous and strongly cut with white lines between the veins.
Wingspan: 23-32 mm (Fernald, 1896); 28 mm (Forbes, 1923); 21-25 mm (Ainslie, 1924).
Adult Structural Features: Ainslie (1924) has descriptions of the male and female genitalia.
Adult ID Requirements: Identifiable from good quality photos of unworn specimens.
Immatures and Development: The following information on the life cycle is based on Ainslie (1927), who mostly worked with captive animals. Local populations can produce from one to perhaps three generations per year depending on the length of the growing season and local conditions, but two seems to be the norm in most regions. The larvae of the last brood overwinter and resume growth in the spring. Ainslie (1927) noted that the time from egg deposition to the emergence of adults varied from 33-46 days based on his rearing records, with the larvae having seven or eight instars. Females produce an average of around 200-220 dry eggs and drop them from the air while fluttering about from dusk into the early evening. The ribbed eggs are almost pure white when first laid but darken to a dull orange within three days, with hatching occurring after seven days.

The hatchlings first create small pits on the grass blades that are soon elongated into grooves that the larvae cover with a loose network of silk and frass. The first two or three instars skeletonize the grass blades, while the later feeding stages construct a tube made of silk, soil and frass. The feeding tubes rest on or just beneath the soil surface and radiate away from the stem. From there the larvae cut off leaves and drag them to their tubes to consume. As the tubes fill with frass from the rear, the larvae abandon these and construct replacement tubes, with a total of four or five used by a single larva during the entire larval period. The larvae of various instars overwintered in a tightly woven, spherical case made of silk and soil particles. The case is either made in one of the tubes, or outside the tube in a sheltered crevice such as a soil clod or pile of grass stems. The larvae abandon the cases following the spring warm-up and continue feeding, then pupate in a silk cocoon that stands vertically below the soil surface and is usually close to the feeding tubes. It has a connecting neck to the soil surface and has a silk valve that allows the adult to escape.
Distribution in North Carolina
Distribution: Pediasia trisecta is broadly distributed across much of the U.S. and southern Canada. This species occurs from coast to coast in Canada and across most on the U.S. from a line from South Carolina, Georgia and the Florida Panhandle westward across northern Texas to central California, then northward to the Canadian border from Washington to Maine. As of 2023, we have only four state records, including one from the Piedmont and a cluster of records from the southwestern Blue Ridge.
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
Flight Comments: The adults fly from April through October in different areas of the range. As of 2023, our records are from a brief flight period of late-July to mid-August.
Habitats and Life History
Habitats: This species appears to rely heavily on grasses as hosts and is strongly affiliated with grassy habitats such as meadows, lawns, pastures and roadways.
Larval Host Plants: The larvae appear to feed mostly on a wide variety of grasses, but will also eat herbaceous species. They can reach high densities and cause significant destruction to cultivated corn and oats, as well as pastures, meadows and lawns (Ainslie,1927; Heinrichs and Southards, 1970). Most information on host use is based on rearings in the laboratory. Ainslie (1927) noted that the larvae will readily eat Kentucky Bluegrass (Poa pratensis), Orchard Grass (Dactylis glomeratus), Timothy (Phleum pretense), Hairy Crabgrass (Digitaria sanguinalis), as well as oats, wheat, rye, barley and corn. They also will accept White Sweetclover (Melilotus albus), Sheep Sorrel (Rumex acetosella) and the roots of clovers (Trifolium spp.). - View
Observation Methods: The adults are attracted to lights.
Wikipedia
Status in North Carolina
Natural Heritage Program Status:
Natural Heritage Program Ranks: GNR [S3]
State Protection: Has no legal protection, although permits are required to collect it on state parks and other public lands.
Comments: The species is uncommon in North Carolina where it is near the southern limit of its range.