Hiking around on an oak-savanna property recently acquired by the Nature Conservancy out in the Glacial Lakes area, our group spotted what they thought was a hummingbird hovering over flowers of the Bladder Campion.
It hovered just like a hummingbird, but it’s not a bird. It’s a hummingbird moth, AKA the White-lined Sphinx Moth. It’s difficult to see the striking white lines on its wings in this photo, but the white lined pattern on its thorax is also distinctive.
It is rather large, for a moth, with a wingspan of 3-4 inches. Like a hummingbird, the moth flitted from flower to flower, pausing only briefly to insert its extremely long proboscis to test for the presence of nectar before moving on. A very difficult subject to photograph!
A closer view reveals that this moth has a proboscis that is even longer than its body length. Adults seek nectar from a variety of sources including columbines, larkspurs, petunia, honeysuckle, lilac, clovers, thistles, and Jimson weed. And they are not particularly fussy about where they live — in open habitats in deserts, horticultural gardens, or even suburban homes.
Later, while walking around a different prairie a few miles away, one of the group discovered a very large green caterpillar munching on a fragile wildflower.
The caterpillar was about 3-4 inches long and almost 1/2 inch in diameter, probably almost big enough to pupate. The orange horn sticks up on its rear end; the head is tucked in and hidden.
This is most likely the caterpillar of a White-lined Sphinx Moth; they can be highly variable in color but the orange horn is a key feature of this species.
It takes about 8 weeks to grow into a caterpillar this large from an egg. Most likely this one overwintered as a caterpillar to complete its development this spring. Once the caterpillars reach a critical size, they pupate underground and emerge as adults in 2-3 weeks. Mated females then begin the cycle all over again, laying up to 1000 eggs on a variety of host plants (e.g, four o’clocks, purslane, fuschia, evening primrose, elm, grape, and tomato) while sustaining themselves on flower nectar.
Back Yard Biology 