Tuesday, October 08, 2013

Goldenrods and their Dependent Fauna

Blue-winged wasp on goldenrod

Goldenrods are magnets for a wide variety of animal life. I am talking about the six-legged and eight-legged fauna, insects and spiders.

I enjoy leading walks in the fall to observe all the bounty of tiny wildlife buzzing, zipping along, and crawling and hiding in the goldenrod patch. I call this program "The goldenrod zoo". My favorites are the pollinators; but I also like to point out the various kinds of galls and their amazing makers and residents.

Goldenrods used to be regarded as weeds in North America; many people still see them that way. Recently I heard a gardener, an organic gardener at that, who wants to eliminate them from her property. This made me think about the beneficial qualities of goldenrods, both to wildlife in general and to gardens in particular. So I started a list.
Goldenrod round galls in winter. One of them has been opened by a chickadee

Round galls are produced in the stems of tall goldenrods by a species of flies (the goldenrod fly). Gail Eichelberger described the fly’s life cycle in "The Gall of That Goldenrod" in "Beautiful Wildllife Garden." She also mentioned how the gall fly larvae can serve as food for chickadees and downy woodpeckers during the winter months. I will simply add that you can tell which of these two birds has opened each gall. Downies skillfully chisel a clean hole, while chickadees are sloppier, and destroy a good part of the gall to get to the prize.

There are a few other types of galls, produced by moths or flies, many of these insects also provide food for birds.
Sweat bee Agapostemon

Sweat bee Augochloropsis
Let us take a look at the goldenrod flowers visitors. There are at least 380 species that visit just one species, the Canada goldenrod (Solidago Canadensis). Not all of them are pollinators and many visit other flowers besides goldenrod. But they all benefit from these flowers’ nectar and pollen.
Syrphid fly, a good aphid control

Feather-legged fly, Tachinidae

Leaf-footed bug. Notice the tachinid fly eggs on its head
Here I am listing a few whose larvae feed on other insects, so they provide an important ecosystem service as biological controls. The larvae of some Syrphid flies feed on aphids. Tachinid flies lay their eggs on other insects especially on stink bugs or related bugs which feed on plants.

Potter wasp

Wasps of many kinds are very abundant in the fall, so perhaps they are the most common visitors of goldenrod flowers. They include not just the more familiar and feared ones, hornets and yellow jackets, but also many solitary ones, which are less likely to sting. All of them catch insects or spiders to feed their larvae.

There is one in particular that has become a favorite of mine, the large and colorful blue-winged wasp, Scolia dubia. It is rather hairy and heavy-bodied, unlike most wasps. Its wings are supposedly blue, as the name suggests. But you need a little imagination, or the sunlight hitting them just right; otherwise they look smoky. The body is very dark blue-black, except for the last few segments of the abdomen which are reddish or orange with two bright large yellow spots.

The nice thing about this wasp is that its offspring feeds on the larvae of June beetles. The females spend a good deal of time searching the ground for beetle larvae and digging them out; this earns them their other common name: digger wasp. When a female wasp finds a grub, it paralyzes it. Then it digs a little deeper, builds a small chamber, and lays an egg on its victim. Gruesome, yes, but effective.

And here comes the best part: The blue-winged wasp has developed a taste for Japanese beetles and treats them the same way as June beetles. We all know that one of the most serious problems with introduced pests such as this is that they have left most of their enemies behind in the old country, so they can multiply unchecked. The USDA tried unsuccessfully to introduce some relatives of this wasp as biocontrols of the Japanese beetle. So it is wonderful to see that a native insect has become an enemy of the invasive pest.
Blue-winged wasp
Here’s to the blue-winged wasp and to the goldenrods that sustain it in the fall!

First published in "Native Plants and Wildlife Gardens" as "Goldenrod, a Weed or a Treasure?"

Beginners Guide to Pollinators and Other Flower Visitors

All photos by Beatriz Moisset. All rights reserved
© Beatriz Moisset. 2013

No comments: