Dainty Sulphur Butterfly – Nathalis iole
Early February near San Antonio, Texas – dainty sulphur butterflies mating. Male is on Left
The Extreme Miniaturization of Pierid Anatomy is obvious with my fingerprint for scale
Also commonly called Dwarf Yellow. Life Cycle: Caterpillar ranges up to 5/8″, dark green with purple stripes on its back, and parallel black and yellow stripes on the side. Caterpillars feed on sneezeweed, both bur and garden variety marigolds, pinks and chickweeds. Chrysalis is smooth, green [3].
Why Dainty Sulphurs Mate Where They Do
February 11, 2003 at San Antonio, Texas. Ambient temperature 65 degrees, sunny. This mating pair was found in a dry creek bed.
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Nathalis iole prefers ground-level microclimates where early-season thermal gain is highest.
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These sites warm faster than vegetation, allowing earlier daily activity.
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Mating on warm rock lowers metabolic cost and accelerates post-coupling recovery.
Male specimen about 14mm
Flight: Year-round in south, later northward. Habitat: Disturbed areas, grasslands, canyons, dry streambeds, watercourses, railroad rights-of-way. Range: Resident in southern California, Arizona and Gulf States, south into Mexico. Emigrants to Midwest and Manitoba; rarely into northwest or northeast U.S.
Male Nathalis iole on Persian Speedwell (Veronica persica)
Dwarf Yellows emigrate northwards every spring following river corridors. They reproduce rapidly and can live in dry, weedy areas. Yet they cannot withstand cold weather, and die off every autumn.
This dainty sulphur is still active at the end of October in northern Illinois. Size: ~14mm
The dainty sulphur butterfly is the smallest North American Pierid [3]
This is near the northern fringe of its migratory reach. Individuals like this are the remnants of that year’s northward expansion, surviving on whatever warmth the season allows before the first killing frost ends the experiment.
References
- Bugguide.net, dwarf yellow butterfly
- National Audubon Society Field Guide to Insects & Spiders Chanticleer Press 1980
- Eric Eaton & Ken Kaufman, Kaufman Field Guide to Insects of North America
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