Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Clickable Guide
Moths Butterflies Flies Caterpillars Flies Dragonflies Flies Mantids Cockroaches Bees and Wasps Walkingsticks Earwigs Ants Termites Hoppers and Kin Hoppers and Kin Beetles True Bugs Fleas Grasshoppers and Kin Ticks Spiders Scorpions Centipedes Millipedes

Upcoming Events

See Moth submissions from National Moth Week 2023

Photos of insects and people from the 2022 BugGuide gathering in New Mexico, July 20-24

Photos of insects and people from the Spring 2021 gathering in Louisiana, April 28-May 2

Photos of insects and people from the 2019 gathering in Louisiana, July 25-27

Photos of insects and people from the 2018 gathering in Virginia, July 27-29

Photos of insects and people from the 2015 gathering in Wisconsin, July 10-12

Previous events


Species Nematocampa resistaria - Horned Spanworm - Hodges#7010

white tan textured moth - Nematocampa resistaria Horned Spanworm Moth - Nematocampa resistaria Brown and White Moth   - Nematocampa resistaria Horned Spanworm Moth - Hodges #7010 - Nematocampa resistaria Nematocampa resistaria Nematocampa resistaria Horned Spanworm - Hodges#7010 (Nematocampa resistaria) - Nematocampa resistaria Geranium caterpillar - Nematocampa resistaria
Show images of: caterpillars · adults · both
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Lepidoptera (Butterflies and Moths)
Superfamily Geometroidea (Geometrid and Swallowtail Moths)
Family Geometridae (Geometrid Moths)
Subfamily Ennominae
Tribe Cassymini
Genus Nematocampa (Filament Bearers)
Species resistaria (Horned Spanworm - Hodges#7010)
Hodges Number
Other Common Names
Filament Bearer (caterpillar)
Synonyms and other taxonomic changes
Nematocampa resistaria (Herrich-Schäffer, [1856])
Nematocampa limbata (formerly lumped with this Eurasian species)
Ferguson (1993) revised the NA species of Nematocampa and was the author who revised the status of the species commonly called N. limbata to N. resistaria.
Wingspan 19-25 mm
Yellowish with distinctive pattern--see photo. Note especially the single am line and the double pm line--the latter far apart at costa, almost touching below it, then separating again. Dark coloration beyond pm line variably purple to brown (1).
A dimorphic species, both between sexes (sexual dimorphism) and within the males; dimorphism in females rare.
Ferguson (1993) describes this species as follows “This widespread nearctic species is distinguished by the whitish ground color of nearly all females (with rare exceptions) to the more yellowish males.” BugGuide image #40816 is a female:

Males vary from having dark blotches--images in Covell (1) and BugGuide images below, showing some of the variability,

to having none - described by Ferguson as “brown markings well developed to obsolescent”. Such markings are geographically variable that has led to them being named as separate subspecies and species.

Strange! Eversible tentacles extend from the dorsal surface of A2 and A3. In the first photo (below, left) they are in the 'relaxed' condition; when the caterpillar is alarmed these tentacles can be extended to 2x their resting length (below, right). These same structures probably occur in other species in the genus; but otherwise I believe they may be unique.
Includes eastern North America. Listed as local and uncommon (1). Reasonably common in NB, seen every year in Fredericton. Also found in Eurasia, depending on taxonomic treatment (see Remarks).
Nova Scotia to Vancouver Island, south to Florida and west to Texas and Colorado. Utah and Oregon but not California. The California species is N. brehmeata(2)
Deciduous forests and coniferous forests.
Appears to be bivoltine on Block Island, RI, with a peak in abundance in July and at least a partial second generation in August and September.(3)
Larvae feed on many hardwoods and several softwood species of shrubs and trees including
pine, hemlock, fir, larch and spruce(2); also low-growing plants as well as alder, ash, basswood, birch, blueberry, buckeye, carrot, cherry, chestnut, dogwood, elm, gale, hawthorn, hazelnut, hickory, ironwood, maple, mountain ash, New Jersey Tea, oak, strawberry, sycamore, willow(4)
See Also
Nematocampa brehmeata which is very similar, but is restricted to central and northern Califonia west of the Sierra Nevada.
Print References
Covell, p. 373, plate 54 #12--listed as N. limbata (1)
Ferguson,D.C. 1993. A revision of the species of Nematocampa (Geometridae; Ennominae) occurring in the United States and Canada. J. Lep. Soc 47(1):60-77. (5)
Miller, p. 54, #75--N. resistaria (6)
Wagner, p. 194--photo of caterpillar and adult specimen (4)
Works Cited
1.Peterson Field Guides: Eastern Moths
Charles V. Covell. 1984. Houghton Mifflin Company.
2.The Moths of America North of Mexico, Fascicle 17.2, Geometroidea, Geometridae, Ennominae.
Douglas C. Ferguson . 2008. The Wedge Entomological Research Foundation.
3.Block Island Moths
4.Caterpillars of Eastern North America
David L. Wagner. 2005. Princeton University Press.
5.A revision of the species of Nematocampa (Geometridae: Ennominae) occurring in the United States and Canada
Douglas C. Ferguson . 1993. Journal of the Lepidopterist Society, 47: 60-77.
6.Macromoths of Northwest Forests and Woodlands
Jeffrey Miller, Paul Hammond. 2000. USDA Forest Service, FHTET-98-18.
7.North American Moth Photographers Group
8.Butterflies of North America