Saturday, July 21, 2012


We've been studying robber flies for years, and now, starting last year and continuing this year, we have begun studying grasshoppers. What a difference. We have gone from a top predator to the bottom of the food chain. Robber flies eat every insect they can catch, and it is surprising what big fierce insects they go after; grasshoppers are eaten by virtually everything, even human beings in many parts of the world, perhaps eventually even here. It's like studying lions, then switching to wildebeests.

The first thing I notice is, you might go into a meadow and see fifty or a hundred grasshoppers, and only five or ten robber flies. These are of course typical predator/prey ratios. A robber fly might eat a hundred insects in its lifetime, and so it needs these numbers. And it won't want stiff competition from other predators, so individuals will space themselves out.

There is also a life history difference. Robber flies have full metamorphosis. For a year or a couple of years they are out of sight as larvae living underground or inside rotting logs feeding on beetle larvae. We only see them when they emerge for a relatively short time as adults. Grasshoppers have partial metamorphosis, which means they are present, often, all summer long as nymphs, chomping on grass mainly, just as they will when they are adults. They are in fact small wingless sexless versions of the adults (but very difficult to identify till they reach their final stages). There are some species that overwinter as nymphs and emerge as adults in the spring, but most are only now, as we get into July, becoming adults with wings and functional genitals and identifiable markings so we have  some chance to learn what they are. It sometimes seems to us like we have been waiting a very long time for the season to finally begin.

But now it is beginning to happen. For a long time there was a skittering of tiny nymphs ahead of us when we walked through the garden, but with each instar they looked more like the adults they would become, and now, one after the other, they are becoming adults. Here are some of the ones that are around now just in our garden.

Grasshoppers are divided into three major groups. First, the Slant-faced Grasshoppers, generally rather small, often slender species with a slanting facial profile, usually staying in thick vegetation. The first ones out in our garden were Short-winged Green Grasshoppers. Here is the female and smaller male. They are around half an inch long, and you can clearly see the slanting face.

The next slant-face out, larger and more elaborate, is the Handsome Grasshopper. These are very common everywhere, especially in short grass. Because they are large enough to have some meat on them, but still not as burly and powerful as some of the larger grasshoppers, they are a favorite prey of jumping spiders and robber flies.

The next major group is the Band-winged Grasshoppers. These are medium to large grasshoppers with long wings which are often brightly colored (orange, yellow, blue) and they can look rather like butterflies when they are in flight. Sometimes they hover in one place for an extended period, trying to look attractive for any females around. These are species of wide open places, fields, barrens, beaches, which is why we don't have many in our closely planted garden. Here, however, is the Northern Green-striped Grasshopper, which is common almost everywhere, and is probably the commonest grasshopper in the state if not in the nation. They can be recognized by the line through the eye that gives them a sad expression, and the blade-like keel that sticks up on their pronotum (the saddle-like structure over their thorax). The females are usually some shade of green, and the smaller males some shade of brown.

The last of the three major groups are the Spur-throated Grasshoppers. These include some of the commonest, and some of the most agriculturally destructive grasshoppers. If you have a garden, and if you let it run a little bit wild, you are likely to have the next grasshopper I am going to figure here, the Differential Grasshopper, and if your garden is like ours, you are going to have so many of them, they are going to eat you out of house and home and drive you to despair, but not, I hope, to the extent of using insecticides, which will also kill everything else in your yard. I don't know what this year will bring, but we have in the past, in really bad years, gathered them in mason jars, and carried them to the other side of the woods across the road from us, and released them. Here is a big heavy hungry Differential Grasshopper, easily recognizable by its size, and the jet black herringbone pattern on its hind leg.

There is a huge number of species, and a huge variety of sizes and shapes among the spur-throated grasshoppers, but they all have in common a little lump (the "spur") that sticks up between their front legs. I will change the angle of the above photograph so you can see the little yellow lump catching the light on both of these.

There is another spur-throat common in our garden now, very different in appearance from the Differential, and that is, the Olive-green Swamp Grasshopper. I enjoy having them here because they are quite attractive and interesting in their behavior, and also because the published range maps show them as occurring in the eastern half of the U.S., but not crossing the Mississippi to enter Arkansas.

In fact, just in our initial explorations we are finding the maps so inaccurate and incomplete I suspect very little work has been done on grasshoppers in Arkansas, and suspect if we stay with it we will be able to make some contributions to science, which is really fun for amateurs like us.

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