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10 - Clouded Sulphur Butterflies Appear

This is one of the earliest butterflies to make its spring appearance in our area (at least among those that don't overwinter). While a few over-achieving specimens can be encountered in February they are far more common in March and early April.

Clouded Sulphurs are occasional pests of clover and alfalfa fields but are on the whole benign. Females lay eggs from April to October in our area so there are many generations of butterflies. Those caterpillars born in spring and summer mature to their adult forms that same season, while those born later munch themselves to maturity and then overwinter in the chrysalis stage to appear the following spring. Exactly how the larvae know what to do, and what cues they use to determine it, are currently unknown - like so much of nature - so here's another master's thesis just waiting for a researcher to unravel the mystery.

From our Archive: Butterfly Gardening

Offsite Links:

• Illinois Butterfly Monotoring Network's Clouded Sulphur sub-gallery
• Nearartica.com Clouded Sulphur page, including range map

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