Moths of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

View PDF	Crambidae Members:	Petrophila Members:	67 NC Records
Petrophila canadensis (Munroe, 1972) - Canadian Petrophila

Taxonomy

Family:
Crambidae

Subfamily:
Acentropinae

Tribe:
Argyractini

P3 Number:
80a1345

MONA Number:
4779.00

Identification

Field Guide Descriptions:

Online Resources: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLD

Technical Description, Adults: Lavery (1973)

Technical Description, Immature Stages: Lavery (1973)

Adult Markings: Petrophila canadensis is a member of the Petrophila fulicalis group as defined by Sexton (2021) and has rather complex wing patterning that is generally similar to that of other members of the group. The forewing has a conspicuous white median band that is often jagged. The white median band adjoins a broad, diffuse, brown antemedian band, which in turn is followed by a broad, whitish post-basal band that is margined basally by a relatively thin dark line. The very base of the wing is typically whitish, with varying levels of darker dusting. The white median band is margined apically by a thin brownish line. The line frequently forms the basal edge of a whitish elliptical loop (discal bar on Munroe, 1972) in the subcostal region. The loop is surrounded by darker pigmentation and often bisected, with the apical half orangish and the basal half white. One or two additional elliptical loops are occasionally present on the apical third of the wing. The apical third of the wing has a mixture of whitish and brown or orangish markings. These include a gradually narrowing, dark triangular mark that extends from the subapical region towards the tornus. It parallels similar white triangular marks of either side. Other conspicuous marks include an orangish terminal band that parallels the outer margin, and a similar orangish tornal bar or wedge that runs perpendicular to the terminal band. The two orangish bands are typically connected near the tornus to form an L-shaped mark. Varying levels of dark speckling are also present on the dorsal half of the wing. The patterning on the basal three-fifths of the hindwing matches that on the forewing. The apical half differs in having more conspicuous dark speckling that is mostly confined to the costal half of the wing, and a series of five subterminal black spots with lighter centers. A thin dark-brown or black capline is present over the eyespots that is variably expressed, and often broken or incomplete.

Petrophila canadensis is the only Petrophila species that has been documented in North Carolina as of 2024. Petrophila fulicalis and P. bifascialis are two related forms that have been found in eastern Tennessee and might be present in the western mountains. Sexton (2021) has distribution maps and information on how to distinguished between these three species.

Adult Structural Features: Heppner (1976) has illustrations of the male and female genitalia (Figures 9a, 9b, and 13), but misidentified these as “P. fulicalis”; they were actually P. canadensis from West Virginia (Sexton, 2021).

Structural photos

Adult ID Requirements: Identifiable from good quality photos of unworn specimens.

Immatures and Development: Lavery (1973) conducted a comprehensive life history study of this species in New York where there are two generations produced per year. The larvae are aquatic and live in fast-flowing streams with rocky substrates. The adults mate at night on the leaves of streamside vegetation and the mated females dive into the water at night and cement their eggs in irregular rows to the tops and sides of submerged rocks. The scaled legs are used as oars and an air bubble is carried between the wings as a source of oxygen. Females have clutch sizes of around 200-300 eggs, and development to hatching requires around 10-13 days depending on the water temperature.

Within a day after hatching the larva spins a webbed case over itself and feeds beneath the shelter. The case is grayish, densely woven, and is expanded to become as large as 6-10 cm long and 3-5 cm wide as the gilled larva grows and passes through five instars. The cases are constructed on the surfaces of algae-covered rocks, and the larvae feed on algae and diatoms on the rock surface. The final-instar larva eventually constructs a pupal cocoon that consists of an inner cocoon that is suspended from a dome-shaped outer covering. Holes are cut in the dome to allow water to pass through. As water flows through, fine silk threads on the outer covering trap tiny air bubbles that eventually form a single large air bubble that surrounds the pupa. The pupal stage last around 11 days, and the adult emerges shortly after dark through a crescent-shaped slit that was cut by the final instar. The adults float to the water surface, apparently using the air bubble as a float, then skitter to the bank or an exposed rock and dry their wings.

In this study, eggs that were laid in August and September hatched quickly and the larvae grew rapidly until October when the arrival of cold weather arrested growth until the following May. Overwintering occurred in a modified winter silken shelter that was several times thicker than the summer shelters. Growth resumed in May and the adults emerged the first week of June, with emergence occurring for about a month thereafter. Eggs laid by the overwintering females hatched quickly and the larvae grew extremely fast, with a second group of adults emerging from 31 July to 10 September.

The larvae can occur at high densities in riffle sections of streams and the adults often have mass emergences with thousands of individuals covering rocks or streamside vegetation. A mass emergence in 2023 was witnessed along the Haw River in Alamance County by Carol Ann McCormick and others where tens of thousands of adults were observed flying about and resting on streamside vegetation.

Larvae ID Requirements: Identifiable from close inspection of specimens or by DNA analysis.

Distribution in North Carolina


Distribution: Petrophila canadensis is found in eastern North America, including portions of southern Canada from southern Manitoba eastward to Nova Scotia and Prince Edward Island. In the US it occurs from Minnesota eastward across the Great Lakes region to the New England states, and southward and westward to Illinois, Indiana, Kentucky, central and eastern Tennessee, central Alabama, northern South Carolina, and North Carolina. This species is mostly found east of the Mississippi River and is generally absent from most or all of the southeastern Coastal Plain. As of 2024, all but one of our records are from lower-elevation sites in the Blue Ridge and rocky stream sites in the Piedmont. We have one Coastal Plain record near the interface with the eastern Piedmont.
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 have been observed from April through September in different areas of the range, with a seasonal peak commonly in June and July. Local populations in North Carolina appear to be bivoltine. As of 2024, our records extend from late-April to late-September.

Habitats and Life History

Habitats: Local populations are found in and around streams and rivers, particularly those with rocky substrates and riffles.

Larval Host Plants: The larvae feed on algae and diatoms that coat the surfaces of submerged rocks (Lavery, 1973). - View

Observation Methods: The adults are attracted to lights and the larvae can be found by inspecting the tops and lateral sides of rocks for cases in streams.

Wikipedia

See also Habitat Account for Piedmont and General Rocky Rivers

Status in North Carolina

Natural Heritage Program Status:

Natural Heritage Program Ranks: GNR[S2S3]

State Protection:

Comments: This species is unusual in having aquatic larvae that live in the riffle sections of fast-flowing streams. They can be locally abundant where the appropriate habitats are present.

Photo Gallery for Petrophila canadensis - Canadian Petrophila		66 photos are available. Only the most recent 30 are shown.
	Recorded by: David George, Jeff Niznik on 2024-09-21 Chatham Co. Comment:	Recorded by: Jim Petranka, Mark Basinger and Becky Elkin on 2024-09-20 Madison Co. Comment:
	Recorded by: Jim Petranka, Mark Basinger and Becky Elkin on 2024-09-20 Madison Co. Comment:	Recorded by: Mark Basinger on 2024-08-09 Mitchell Co. Comment:
	Recorded by: Mark Basinger on 2024-08-04 Mitchell Co. Comment:	Recorded by: Mark Basinger on 2024-08-04 Mitchell Co. Comment:
	Recorded by: David George, Jeff Niznik, Stephen Dunn on 2024-08-02 Chatham Co. Comment:	Recorded by: David George, Jeff Niznik, Patrick Coin, Steve Hall, Carol Tingley, Tom Howard on 2024-07-27 Chatham Co. Comment:
	Recorded by: Jeff Niznik on 2024-07-26 Alamance Co. Comment:	Recorded by: David George on 2024-07-04 Chatham Co. Comment:
	Recorded by: David George, Jeff Niznik, Stephen Dunn on 2024-06-29 Chatham Co. Comment:	Recorded by: David George, Stephen Dunn, Jeff Niznik, Patrick Coin on 2024-06-22 Chatham Co. Comment:
	Recorded by: David George, Stephen Dunn, Jeff Niznik, Patrick Coin on 2024-06-22 Chatham Co. Comment:	Recorded by: David George, Stephen Dunn, Jeff Niznik, Patrick Coin on 2024-06-22 Chatham Co. Comment:
	Recorded by: Jim Petranka on 2024-06-12 Madison Co. Comment:	Recorded by: David George, Jeff Niznik on 2024-06-10 Chatham Co. Comment:
	Recorded by: Jim Petranka on 2024-06-05 Madison Co. Comment:	Recorded by: Dean Furbish on 2024-06-01 Orange Co. Comment:
	Recorded by: David George, Jeff Niznik on 2024-05-25 Chatham Co. Comment:	Recorded by: David George, Rich Teper on 2024-05-13 Chatham Co. Comment:
	Recorded by: David George, Rich Teper on 2024-05-13 Chatham Co. Comment:	Recorded by: David George, Stephen Dunn, Jeff Niznik on 2024-04-29 Chatham Co. Comment:
	Recorded by: David George, Stephen Dunn, Jeff Niznik on 2024-04-29 Chatham Co. Comment:	Recorded by: Jim Petranka and Becky Elkin on 2023-09-25 Madison Co. Comment:
	Recorded by: Stephen Dunn, Jeff Niznik on 2023-07-26 Chatham Co. Comment:	Recorded by: Stephen Dunn, Jeff Niznik on 2023-07-26 Chatham Co. Comment:
	Recorded by: John Petranka, David George, Sally Gewalt on 2023-04-24 Alamance Co. Comment: One of tens of thousands of individuals that had recently emerged from the Haw River.	Recorded by: John Petranka, David George, Sally Gewalt on 2023-04-24 Alamance Co. Comment:
	Recorded by: John Petranka, David George, Sally Gewalt on 2023-04-24 Alamance Co. Comment: One of tens of thousands of individuals that had recently emerged from the Haw River.	Recorded by: Carol Ann McCormick on 2023-04-23 Alamance Co. Comment: There were thousands of these small moths along the banks of the Haw River. There were clouds of them, close to the edge of the river.

Petrophila canadensis (Munroe, 1972) - Canadian Petrophila

Photo Gallery for Petrophila canadensis - Canadian Petrophila

66 photos are available. Only the most recent 30 are shown.