Hyalophora euryalus

Boisduval, 1855

Ceanothus silkmoth, Ceanothus silk moth

Species Guides

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Hyalophora euryalus, the ceanothus silkmoth, is a large saturniid native to western North America. lack functional mouthparts and do not feed, living solely to reproduce. The is notable for its broad plant range spanning multiple plant . Larvae possess and scoli that can cause skin irritation. The moth has a single per year, with adults active from January through July depending on latitude and elevation.

Hyalophora euryalus euryalus by (c) Barbara Banfield, some rights reserved (CC BY), uploaded by Barbara Banfield. Used under a CC-BY license.Hyalophora euryalus by (c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda. Used under a CC-BY license.Hyalophora euryalus 320975204 by Aiva Noringseth. Used under a CC BY 4.0 license.

Pronunciation

How to pronounce Hyalophora euryalus: /haɪˌæləˈfɔrə juˈriːələs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other Hyalophora by geographic range (western North America vs. eastern/central for H. cecropia and H. gloveri). H. euryalus occurs in drier intermontane compared to the more mesic-forest associated H. cecropia. active earlier in the year (January–July) than H. cecropia (spring–early summer in most of range). Wing pattern and coloration variable but generally with more extensive reddish tones than H. gloveri. Larval plant association with Ceanothus is characteristic but not exclusive.

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Habitat

Dry intermontane valleys and interior regions. Associated with montane and foothill where plants occur. Found in areas with sufficient moisture to support host vegetation, including riparian corridors and mesic slopes within otherwise dry regions.

Distribution

Western North America from interior British Columbia (north to Prince George along Fraser River) south through Washington, Oregon, California to Baja California, Mexico. Absent from coastal Pacific Northwest and most of the Great Basin desert proper.

Seasonality

on wing from January to July depending on location, with earlier at lower elevations and southern latitudes. Single per year (). Overwinters as pupa within cocoon.

Diet

Larvae feed on leaves of Ceanothus (Rhamnaceae), Rhamnus californica (Rhamnaceae), Prunus emarginata (Rosaceae), Arctostaphylos (Ericaceae), Alnus (Betulaceae), Betula (Betulaceae), Corylus (Betulaceae), Ribes (Grossulariaceae), Pseudotsuga menziesii (Pinaceae), Arbutus menziesii (Ericaceae), Liquidambar (Altingiaceae), and Salix (Salicaceae). do not feed.

Host Associations

  • Ceanothus - larval Primary namesake
  • Rhamnus californica - larval
  • Prunus emarginata - larval
  • Arctostaphylos - larval
  • Alnus - larval
  • Betula - larval
  • Corylus - larval
  • Ribes - larval
  • Pseudotsuga menziesii - larval
  • Arbutus menziesii - larval
  • Liquidambar - larval
  • Salix - larval

Life Cycle

Complete with four stages: , larva, pupa, . Eggs deposited in clusters on leaves of plants. Larvae progress through five instars, feeding gregariously in early instars, becoming solitary in later instars. occurs within a silken cocoon attached to vegetation, often with incorporated leaf fragments. Adults emerge following winter , with timing dependent on temperature accumulation. Single per year throughout range.

Behavior

are and strongly attracted to light. Males detect female using their large, feathery . Larvae may exhibit gregarious feeding in early instars, dispersing as they develop. Defensive include thrashing and use of urticating setae.

Ecological Role

Larvae function as herbivores, consuming foliage of diverse woody plants. serve as prey for birds, bats, and other . Pupae in cocoons may be consumed by small mammals and birds. The contributes to nutrient cycling through herbivory and serves as a food source in .

Human Relevance

Subject of ecological study due to sensitivity to introduced . Potential impact from Compsilura concinnata, a tachinid fly introduced for gypsy moth biocontrol, has been documented to parasitize related Hyalophora . No direct economic importance; not a pest species. Occasionally encountered by naturalists and enthusiasts.

Similar Taxa

  • Hyalophora cecropiaSimilar large size and general , but restricted to eastern and central North America; differs in preference (more mesic forests) and typical activity period
  • Hyalophora gloveriOverlaps in western range; distinguished by , , and subtle differences in wing pattern and coloration
  • Antheraea polyphemusSimilar large saturniid with eyespots, but distinguished by translucent eyespots on hindwings and different geographic range

More Details

Conservation Concerns

Like other native saturniids, H. euryalus may be vulnerable to by the introduced biocontrol agent Compsilura concinnata, a tachinid fly brought to North America to control gypsy moth (Lymantria dispar). This has been implicated in declines of several giant silk in the northeastern United States. The broader western range of H. euryalus may provide some buffer against regional extirpation.

Taxonomic History

Originally described as Saturnia euryalus by Jean Baptiste Boisduval in 1855. Later transferred to Hyalophora, which currently contains four North American .

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