Crossidius discoideus sayi
Casey, 1912
Crossidius discoideus sayi is a of in the , to western North America. It is recognized as a Batesian mimic of toxic (Chauliognathus spp.), sharing their characteristic orange and black color pattern despite being harmless itself. are active in late summer and early fall, feeding on flower pollen and nectar, particularly from Gutierrezia sarothrae (broom snakeweed). The develop as root-crown borers in their plants.
Pronunciation
How to pronounce Crossidius discoideus sayi: /ˈkrɒsɪdiəs dɪˈskɔɪdiəs ˈseɪaɪ/
These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.
Identification
Distinguished from similar-appearing ( ) by its long —soldier beetles have relatively short, antennae. Separated from other Crossidius by association with its specific Gutierrezia sarothrae and geographic range. The orange and black pattern is shared with several co-occurring species in a Müllerian/ complex.
Habitat
Associated with open, dry where Gutierrezia sarothrae (broom snakeweed) occurs; found in grasslands, sagebrush steppe, and open woodlands at middle elevations. occur on flowering host plants; inhabit root crowns of host plants.
Distribution
Western North America; recorded from California and the southwestern United States including Utah, Arizona, and Nevada. The occurs in the Great Basin and adjacent regions.
Seasonality
active in late summer and early fall, primarily August through September, coinciding with flowering of plants.
Diet
feed on pollen and nectar of flowers, particularly Gutierrezia sarothrae (broom snakeweed). bore in root crowns of Gutierrezia sarothrae and possibly Isocoma .
Host Associations
- Gutierrezia sarothrae - larval (root-crown borer); food source (pollen/nectar)broom snakeweed
- Isocoma spp. - possible larval Jimmyweed
Life Cycle
develop as borers in the root crowns of plants. emerge in late summer to feed on flowers and mate. Detailed information is limited.
Behavior
are and found on flowers of plants. Participates in a complex with toxic and , gaining protection from through resemblance to chemically defended .
Ecological Role
serve as of their plants. As , they are root-crown borers that may influence . Their participation in complexes contributes to learning and -level defense signaling.
Human Relevance
No direct economic importance. Occasionally collected by . The complex involving this has been used as an educational example of in .
Similar Taxa
- Chauliognathus basalisShares orange and black color pattern; distinguished by shorter and different body shape ( )
- Chauliognathus deceptusSimilar color pattern; distinguished by shorter and mountainous/foothill preference
- Epicauta stuartiSimilar black and orange warning coloration; distinguished by more body form, shorter , and () characteristics
- Calopteron terminaleSimilar color pattern; distinguished by -veined characteristic of and different antennal structure
- Crossidius coralinusCongeneric with similar biology and ; distinguished by larger size, more extensive black markings on , and association with Ericameria nauseosa rather than Gutierrezia
- Crossidius pulchellusCongeneric with similar size and ; distinguished by different elytral markings and also associated with Gutierrezia sarothrae
More Details
Mimicry complex
This is a well-documented example of , where a harmless evolves to resemble a toxic or unpalatable model. The model species in this complex appear to be (Chauliognathus spp.) and ( spp.), which possess chemical defenses. The is so effective that the can be difficult to separate from models without close examination.
Taxonomic notes
The was described by Casey in 1912. Some in western Fresno County, California may represent an undescribed subspecies or distinct population, as noted by familiar with the region.