A Little Bit of Blue

Top Photo: Larva on crownbeard.

I was expecting to find larvae of silvery checkerspot as I bent down to look at the usually tall, broad-leafed herbaceous plant with misshaped yellow flowers, crownbeard. I always associate crownbeard with that orange and black butterfly, though I’ve never recorded one here at the museum in my 14 some years of walking past these flowers, it does no harm to look.

When I see this plant along the Eno River, or other wet areas, I do sometimes see silvery checkerspot, in the proper season that is. On this day, all I saw were large red ants at the tips of the plant’s flower buds and petals. If there are ants, there may be nectar or honeydew producing insects present.

Ants attending larva on crownbeard.

Looking closely, I was able to make out a few larvae of some sort, sawfly or butterfly, I didn’t yet know. I asked Ranger Molly if she could see legs on the posterior end of the insects. If so, how many. She said yes and counted five pairs of legs. They were caterpillars and not sawfly larvae.


Next, I needed pictures. Always take as many pictures as you can, from every angle, front, back, sides, top, bottom, without too much disturbance to the subject.

Always get pictures.

Back at the office, the closest I could get to a physical match in my reference guide was hairstreak or blue (Hairstreaks are small butterflies with modified, elongated scales on their hindwings which simulate antennae so as to fool predators into striking at their hindwings and not the head end of the butterfly. Blues are a group of small butterflies with blue on the upper surface of their wings). The caterpillars of both hairstreaks and blues are supposedly highly variable in color.

One written clue in the my reference guide narrowed the search quickly “Blues can be immediately recognized by their minute, white star-shaped setae.” Setae are hairs or spines on the caterpillar. These caterpillars are very small, less than 1/2 inch in length. The hairs or setae are like-wise very tiny. I’m going to have to bring one of the larvae back to the office to get some real close-ups.

I took some macro shots, viewed them on the computer and voila! there were little stars all over these caterpillars, they were blues.

Close-up of skin. Star-shape setae are evident.

There are several small blue butterflies in the area, eastern tailed blue, spring azure, and summer azure. All three are seen here at the museum.

Were they eastern tailed blue or azures? They looked more like azures than they did tailed-blue caterpillars. And, I had seen summer azures recently in the vicinity. I pass this location numerous times daily. More than a few times I witnessed azures flying during my passage of the flowers.

Considering the time of year, the physical appearance of the caterpillars and their attendance by ants, I’d say they were summer azure larvae.

These caterpillars produce a chemical which attracts ants, “convincing” them to stay nearby and protect them from potential predators. At first, they draw in the attendant ants with a good dose of honeydew, doling it out in smaller doses as the ants get “hooked.” They can even withdraw or reabsorb the honeydew so as to not waste the precious liquid and perhaps use the energy it provides themselves.

Ant attempting to collect reward for services rendered.

If you question whether the ants do a good job of watching over the caterpillars, touch your finger to one of the caterpillars. The ants will immediately confront you, climb aboard your hand and bite away. Two of them took me on. The bites were nothing more than minor irritation, but the two ants were moving about my hand furiously as I tried to brush them off. They meant business.

Arrow points to caterpillar under protection of ant.
Ant rushes down stem towards my fingers, jaws agape.

The caterpillars are about 1 cm, or a little less than 1/2” in length and they match their surroundings quite well. If you’re going to look for them, you’ll have to look close. The ants are the best clue to the caterpillar’s presence. If you see ants, look for caterpillars.

Look for the ants.

Good luck!

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