Blue caterpillars come in many different species, but some of the most common blue caterpillars include:
Eastern Tailed Blue
The Eastern Tailed Blue (Cupido comyntas) is one of the most common blue caterpillars. These caterpillars are mostly blue in color with some black spots and reach around 1 inch in length. They feed on plants in the pea family before forming a chrysalis and emerging as butterflies in the summer.
Blue Metalmark
The Blue Metalmark (Calephelis borealis) caterpillar has a vibrant blue color with orange spots. They feed on plants like rattlebox and vetch before forming a chrysalis attached to a leaf. Their range is limited to southern Florida and the Keys.
Mountain Blue
The Mountain Blue (Celastrina echo) caterpillar is steel blue or gray in color with a yellow and black pattern. They reach around 0.5 inches in length and feed on huckleberry, azalea, blueberry, and other plants before forming a chrysalis and emerging as a butterfly in summer months.
Fatal Metalmark
The Fatal Metalmark (Calephelis nemesis) has a bright blue caterpillar covered in raised black spots and black tails. They feed on plants like yellowtop and crotalaria before pupating. Their range is limited to southern Florida and some Caribbean islands.
Bluebottles
Bluebottle caterpillars are any of several swallowtail species that have blue, green, or turquoise larvae with striking eye-spots. Some common species are the Eastern Black Swallowtail, Spicebush Swallowtail, and Zebra Swallowtail.
Marine Blue
The Marine Blue (Leptotes marina) has a greenish-blue caterpillar with white and orange bands and black tufts. They feed on plants like black mangrove and red mangrove. Their range is coastal areas of southern Florida, the Caribbean, and Central America.
Why Are Some Caterpillars Blue?
There are a few leading theories as to why some caterpillars are blue or have blue coloration:
- Camouflage – blue can help caterpillars blend in with blue host plants like blueberries
- Mimicry – blue coloration mimics toxic species as a defense, like the Eastern Tailed Blue resembling the poisonous pipeline swallowtail caterpillar
- Warning coloration – blue indicates toxicity or bad taste to potential predators
- Thermoregulation – blue coloration may help regulate body temperature
- Unknown advantage – blue may serve an unknown evolutionary benefit
Blue Caterpillar Identification Tips
Here are some tips for identifying blue caterpillars:
- Note the color shade – darker navy, powder blue, turquoise, etc.
- Look for distinctive patterns – spots, stripes, banding
- Check for key features – spiny projections, tails
- Watch movement – inchworm motion, sluggish or quick
- Consider length and width
- Observe host plant – caterpillars often match host foliage
- Use location – blue caterpillars have limited ranges
- Consult field guides or online databases if needed
Conclusion
While most caterpillars are green, black or brown, blue coloration does occur in some fascinating species. Blue eastern tailed blues, blue metalmarks, mountain blues and bluebottles offer some of the most vibrant blue caterpillars. Their shades of blue likely serve advantages like camouflage, warning coloration or thermoregulation. With close observation of appearance, behavior and host plants, blue caterpillars can be identified and appreciated for their stunning natural beauty.
