Sand, Dust, Florescence, and Waxy Larvae

A hole in the sand. That’s what I was looking at, a hole in the sand. Ranger Ian had spotted a bee or wasp hovering around and entering a 1/2” hole near the “sandbox” in Gateway Park. I was there to put a name on the bee or wasp and to help determine if the nest would put any children in harm’s way.

Hole in the sand.

It’s a large sandbox where kids use mini backhoes to fill up Tonka trucks with sand and drive them around to be dumped at imaginary construction sites on the far side of the sandbox. The insect’s nest hole was off to the side near a couple of shrubs, out of the way of the construction. I had already determined, or guessed, before my arrival at the site that the insect in question was a species of wasp in the genus Bembix, a group of sand nesting wasps who deliver flies to their larvae buried within sandy burrows.

Incoming wasp.

Bembix wasps are innocuous creatures and it’s my belief you’d truly have to abuse one of these medium-sized wasps for it to sting you. Never the less, we decided to remove the wasp. It was Ian who captured the gentle creature and released it on the far side of the campus. But not before I secured a few photos. I’ll bet it was back in the same spot within minutes.

Several days later, after looking at the photos of the wasp, I’ve had a change of opinion. I now think the wasp was a species belonging to the genus Bicyrtes and not a Bembix species. Bicyrtes are closely related to Bembix. I base the change in id on the shape and size of the white markings on the wasp’s abdomen.

I now think this is in the genus Bicyrtes.

Beside the shape and size of the white markings on their abdomens, the prey the Bicyrtes wasps feed their young is different from Bembix wasps. These wasp mass stock their nests with true bugs. Briefly, true bugs (Hemiptera) are insects with sucking mouth parts. Stink bugs, plant bugs, aphids, and leaf hoppers, among others, are true bugs. As far as temperament, they’re essentially the same wasp, you’d have to sit on one to get stung.

Speaking of sand, while standing at the Red Wolf Overlook, I noticed a brown thrasher lying in a patch of sand inside the enclosure. I’ve seen this behavior before in brown thrashers as well as a few other species of passerine. The bird was readying itself for a dust bath.

First, the birds “belly” into the sand, often spreading their wings or tail feathers and fluffing out their body feathers. They then shake, rattle and roll, letting in as much sand as possible. The sand is worked into their feathers and just as vigorously shaken out again. If you’ve seen a bird take a bath in a birdbath it’s the same thing, except that sand is the medium of choice here.

Brown thrasher taking a dust bath.

Why do some birds do this? It’s been found that in some species it helps to eliminate oil from the feathers. The dust absorbs the oil and is expelled through the bird’s quaking and shaking. It may also serve to rid the bird of lice or other parasites.

The dust flies in this shot (right).

I’ve witnessed brown thrashers dust bathe more often than any other species.

If you’ve walked past our Pollinator Garden here at the Museum (on your left, just past the Farm Yard), you’ve surely noticed a group of bright orange flowers on tall stalks as you strolled by (top banner photo). ¡Naranja brillante!

It’s Mexican sunflower. Don’t simply walk by them though, wait a few seconds, you’re bound to see a bee or wasp visit one of the flowers. The photo below shows a carpenter bee sipping nectar, and in the process, collecting and spreading pollen.

Carpenter bee on Mexican sunflower.

While at the garden, look for purple cone flower (Echinacea purpurea). It, like the Mexican sunflower, is hard to miss. And, like the sunflower, it’s a favorite of bees and wasps. Stick around and you’ll see.

Purple coneflower.
Carpenter bee on purple coneflower.

One of our happy summer campers brought to my attention what looked to be a tiny caterpillar. I was leading a group of campers around the campus pointing out plants, bugs, birds, and whatever else I happened to spot. In a group like this, you usually get one or two, sometimes more, kids who get into what it is you’re trying to get them to do, see and experience the life around them. They soon start pointing out things that they see along the trail, wanting to know what this plant is or that insect.

A tiny caterpillar?

The insect presented to me had a familiar look. I wasn’t sure where or when I’d seen one like it before, but I knew I had. After being lead to the spot at which the insect was collected, things became clearer. There was frass all over the handrail of the boardwalk. The shrub next to and above the boardwalk had nearly been defoliated. From the leaves that remained, I could see the shrub was a silky dogwood. And, there were white, wax covered caterpillars all over the shrub.

Wax covered larvae.

In August of 2015, I came across this same insect on a silky dogwood just fifty yards distance. It was not a caterpillar, it was a sawfly larva. I was looking at a group of dogwood sawfly larvae.

Besides being in entirely different orders of insects (sawfly=hymenoptera, butterfly=lepidoptera), sawfly larvae differ from butterfly and moth larvae in that they have more prolegs. Prolegs are false legs worn by the larvae which help them cling to vegetation as they feed. They’re not retained into adulthood. Butterflies and moths have no more that five pair of prolegs while sawfly larvae have more than five pair of prolegs.

Three pairs of true legs (right, behind head) and more than five pairs of prolegs.

By the way, dogwood sawfly larvae do not carry the waxy substance on their backs in the early larval stages, or in the later larval stage (they molt about four times before pupating). They only wear the white waxy coating during the middle stages of larval development. The white waxy substance has been suggested to be a form of camouflage, mimicking bird droppings. To my eye, it makes the larvae stand out against the green of the dogwood leaves. Any thoughts?

Bird dropping?

There’s life all around you, you just have to open your eyes to see it.

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