Orange sulphur butterfly (Colias eurytheme)
What’s yellow and white and orange all over? This week’s crawly, the orange sulphur butterfly (Colias eurytheme).
What’s in a name? Yes, the orange sulphur is half named for their golden sulfur color. Sulphur is the (normally) British variant spelling of the same element.
Fun fact: Sulfur the element is also known as “brimstone” when burned it melts into a blood red liquid and produces a blue flame.
It’s highly unlikely the same would happen if an orange sulphur butterfly spontaneously combusted.
The orange sulphur is just one of 17 species of sulphurs in the Genus Colias, but the one you’re most likely to see here in Oregon. Orange sulphurs are the most populous and wide-spread sulphurs in the United States.
Of their many cousins, oranges most closely resemble clouded sulphurs who are nearly as widespread, but fewer in number and they don’t live in the southern portion of the U.S. (with a few exceptions).
Orange sulphurs have another nickname, “alfalfa sulphurs” so you might guess they can be pests in alfalfa fields.
Fun fact: Alfalfa is in the pea family (a legume) and is used for nutrient rich hay. Alfalfa accounts for 41% of Oregon’s hay harvest and is primarily grown east of the Cascades. Jackson County produces the most alfalfa west of the Cascades. Alfalfa is the main hay feed used in the dairy industry.
While there are comparatively few orange sulphur butterfly sightings in Oregon as there are in other states, Jackson County residents have a better chance than most folks on “our side of the mountains” to spot one.
Despite their “alfalfa” name, orange sulphurs don’t need alfalfa to thrive. Their caterpillars will chow down on several different pea species such as vetch, white clover and purple clover.
Adult oranges will drink nectar (thus pollinate) flowers in the pea family but also enjoy a wide range of blooms including dandelion, milkweeds, goldenrods and asters.
Orange sulphurs are fascinating flitters who breed year-round in some of their more southern locations. In order to do this, orange sulphurs migrate. When their pea plant food sources dry up in one area, they move on to another. Many migrate short distances into higher elevations where pea plants are still blooming, some must migrate quite far to start their next generation.
Females lay eggs singly on individual pea leaves and the pillars have a particular dining style. Generally they feed at night to evade predators, but that’s not particularly unique. The precise manner in which they consume leaves is sure different though. When they first hatch orange pillars feed by chewing holes in the tips of the host plant leaves. As they grow, we’ll call it the “toddler” stage, they eat the entire leaf tip. The most mature pillars will eat half the leaf then turn and chow down on the other half.
In chillier climates late fall pillars will morph to chrysalis form, then overwinter before hatching out in early spring. The orange sulphurs who hatch out in spring (whether or not they overwinter as chrysalises) will be smaller in size than those who hatch in the warm summer months.
Orange sulphurs vary in size from one and one-quarter inches to two and three-quarter inches. Quite a range!
They also vary in color, especially the females. Some females are so pale they are nearly white with none of the orange coloration that gives them their name. It’s impossible to tell a pale orange sulphur from a pale clouded sulphur female without DNA testing. This explains why there is a lot of hybridizing between orange and clouded sulphurs where their ranges overlap.
Keep your eyes peeled for a POP! of sulfur yellow this spring and summer as you pass one of our area’s alfalfa fields to see one of these golden beauties up close and personal.