Sunday, August 31, 2014

The "Unbeetle" Beetle

© 2007 Beatriz Moisset
The distinguishing feature of all beetles is their hard external shell or coat. They don't seem to have wings. At least none are visible. The delicate, film-like wings of wasps and flies seem absent. But most beetles do have wings and fly quite well. The front wings of most insects have been modified in beetles into a hard case, called elytra, that covers and protects the second pair of wings. Their membranous hind wings remain out of sight, folded like origami. When they are ready to take off, the hinged hard elytra moves out of the way and the unfolded large hind wings are ready to go.

The exception to this rule is a peculiar insect without a common name and with just as peculiar a scientific name, Ripiphorus. In the case of this unusual insect the elytra are reduced to two little nubbins incapable of covering anything. The hind wings are longer than the beetles body, thin and translucent like those of wasps or flies. For lack of cover there is no point in folding them, so they are in plain sight all the time. I wouldn’t expect you to realize that it as a beetle if you are not an entomologist. I remembered being perplexed, myself the first time I saw one of these. You would probably ask: "Is that a wasp, or could it be some kind of fly?"

Male Ripiphorus beetle © 2011 Ilona Loser
 Some Ripiphorus are entirely black, others deep red. The males can be distinguished from the females by their flamboyant, feather-like antennae. Now, let us get back to its name and what it means. It should be spelled Rhipiphorus. Too bad the original author made a mistake and the rules of nomenclature prevent us from changing the original name. In Greek, it means a fan carrier, in reference to the male's impressive antennae. So, let this be its common name.

Female laying eggs. © 2007 Beatriz Moisset
You are more likely to see the females because they live a little longer than the males. They diligently visit flowers, not just any flowers, but only the fresher ones, the ones that are just beginning to open. They have a clever reason for doing this. They lay their eggs inside the blossoms and leave them to fend for themselves.

The newborn is not a defenseless shapeless grub like most beetle larvae. Instead it is mobile, with sharp claws, and can recognize a bee when it sees one. When a pollinator arrives at the flower, a few days later, the larva jumps into action and climbs into it. When the bee arrives at the nest with her load pollen and nectar, the little hitchhiker dismounts, ready to perpetrate its deed. Soon, it proceeds to feed on the bee's growing larvae and it may also consume some of the supplies. This is how a Rhipiphorus beetle makes a living, at the expense of an innocent pollinator's babies. Thus, it is considered a parasitoid, a word derived from parasite, but with a slightly different meaning. A parasite, ordinarily, doesn't kill its victim or host. The parasitoid behaves like a parasite at first but ultimately kills its host.

I feel sorry for the poor pollinator, but realize that this is the way of nature. I accept the behavior of this fascinating beetle and marvel at its strange looks and singular life style.

© 2007 Beatriz Moisset

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Sunday, August 17, 2014

The Mason Wasp and the Caterpillar

Mason wasp, Euodynerus hidalgo and caterpillar
© Beatriz Moisset. 2014
Recently I found a wasp on a sunflower wrestling a caterpillar almost as big as herself into submission. The caterpillar had made considerable damage to the flower head as shown on the pictures. Finally the hunter managed to grip its prey by the throat, if that is where caterpillars have a throat. Carefully tucking her prey under her body, she flew away, presumably to her nest to feed her brood with it.

Caterpillar held firmly behind the head
© Beatriz Moisset. 2014
I identified the hunter as one of the mason wasps, so called because they use clay to build nest partitions. It was a rather small wasp, mostly black with yellow markings on its body. The wings remained folded lengthwise. All members of the family Vespidae do this when not in flight. Now, I finally could decipher the mystery presented to me a year earlier in the same garden where I was doing my observations.

On that occasion, I noticed a mason wasp furiously searching a flower head, almost a carbon copy of the one in front of my eyes. It had the same kind of damage, but, at that point, I didn't know what or who had caused it. The mason wasp rummaged the entire center of the blossom, even burying half of her body in it with no apparent success. After observing these antics for a while I moved on without finding out what she was looking for. Now, I had the answer.

Another mason wasp found a year earlier
© Beatriz Moisset. 2014
 A mother mason wasp, like the one I was observing, builds her nest inside any available hole of the right size, slightly wider than her own body. It could be a hollow stem or some other cavity previously dug up by a beetle or other insect. Unlike their distant cousins, hornets and yellowjackets, they don't form large colonies. Each mother wasp minds her own business, builds a nest where it raises maybe a dozen babies and is not inclined to defend this small investment as ferociously as hornets tend to do. Thus, their presence can be easily tolerated in the garden.

Mason wasp tending her nest

Interestingly the so called mason bees have similar nesting habits. These bees are excellent pollinators of fruit trees and other plants, so gardeners prize their services. Some gardeners provide housing for them by hanging a bundle of hollow twigs or drilling a number of holes in a piece of wood. These bee houses and bee hotels have been growing in popularity in recent years. You can purchase them from several venues usually accompanied by an instructions booklet.

© Beatriz Moisset. 2014
Mason wasps use caterpillars to feed their babies. They keep their prey alive, so the food supply remains fresh as long as needed. They do so by paralyzing but not killing their victims with their stingers, a delicate operation. This is why my wasp was so busy getting the right hold of the caterpillar, firm but not too harsh.

Most adult wasps are often seen on flowers because they feed mostly on nectar. This particular species has another reason for visiting flowers. This is where it finds its prey. Some caterpillars, especially some inchworms and owlet moths, show a preference for sunflower heads. They hide in the very heart of the flower and proceed to eat the growing seeds causing a bit of destruction. It is nice to see that this hunting wasp prey on them preventing further damage.

If you love pollinators you may be raising mason bees. Perhaps you find some of the holes in your bee houses occupied by mason wasps. You may be tempted to destroy the "invaders." Please, don't! You probably didn't know that they help the pollinators by keeping down the populations of plant eating insects. We need biological controls as much as we need pollinators to maintain a healthy garden.

Additional readings
In Praise of Wasps
Urban Bee Gardens. Berkeley University
Nests for Native Bees. The Xerces Society
Bee houses. National Wildlife Federation. (How to build a bee house)

Sellers of bee houses
Knox Cellars.
Mason bee homes.

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014