October 10, 2014 at 6:04 am (plant-eating insects)
Tags: Melanoplus femurrubrum, red-legged grasshopper
by Carl Strang
This is the first year in which I have searched for singing grasshopper species with the same intensity as for cicadas, crickets and katydids. Since the grasshoppers seldom sing, and when they do have essentially identical songs, I have had to learn about the structure of grasshoppers so as to identify them. The most common species in the region seems to be a non-singing one, the red-legged grasshopper. It therefore is an important one to learn about.
Red-legged grasshoppers belong to the spur-throated grasshopper group. Here is a close relative, the pine tree spur-throated grasshopper. The rounded peg between the front legs is the uniting feature of the group. None of the singing grasshoppers possess it.
Here is a red-legged grasshopper female. Female grasshoppers have pointed abdomen tips, formed from the valves of the ovipositor.
Female structures are similar enough that species identification is more difficult. It is best to focus on males.
Note the rounded abdomen tip in the male red-legged grasshopper. The dark, relatively unbanded but somewhat herringbone pattern of the femurs, along with the red tibias and the wing length, are helpful in identifying this species in either gender.
In the male red-legged, the abdomen tip is swollen. The cerci (the pale pair of small structures a bit back from the tip and on top of the abdomen) are shaped like elongated triangles with rounded points.
Viewed from the end, the rounded edges and the U-shaped central depression in the subgenital plate (the structure occupying most of what you see from the end) are diagnostic for the male red-legged grasshopper).
December 10, 2012 at 7:03 am (plant-eating insects, singing insects)
Tags: Allard's ground cricket, Allonemobius allardi, Allonemobius fasciatus, Carolina ground cricket, Chortophaga viridifasciata, common true katydid, dog day cicada, Eunemobius carolinus, first song date, gladiator meadow katydid, greater angle-winged katydid, greenstriped grasshopper, insect phenology, last song date, Linne's cicada, Melanoplus femurrubrum, Metrioptera roeselii, Microcentrum rhombifolium, Oecanthus fultoni, Orchelimum gladiator, Pterophylla camellifolia, red-legged grasshopper, Roesel's katydid, scissor-grinder cicada, snowy tree cricket, striped ground cricket, Tibicen canicularis, Tibicen linnei, Tibicen pruinosa
by Carl Strang
I now have 7 years’ data in which I have noted the first and last dates on which I heard each singing insect species. This year was characterized by a mild winter followed by a warm spring and then a summer of drought. The mild winter and spring apparently were responsible for this year’s early phenology. First song dates were the earliest I have recorded in DuPage County for 17 of the 21 species for which I have 7 years of records. The chi-squared value of 77.33 (with an expected value of 3 species per cell for each rank of earliest to latest) is, of course, statistically significant.
The greater angle-wing started earlier and finished earlier this year than in any of the previous 6 years.
As for last song dates, singing insects generally finished early this year. Of the 20 species for which I have 7 years’ data, 15 had their earliest or second-earliest ending dates, and the chi-squared value was a statistically significant 22.68. This was not a particularly cold or dry late summer and autumn, so the implication is that singing insects have a fixed rate of attrition or duration of song season, so that an early start results in an early finish. The 12 species for which I have the best, most reliable records do have differences in observed song season lengths (ranges for the 7 years, and ranked lowest to highest: 18-42 days for Roesel’s katydid, 16-52 days for gladiator meadow katydid, 52-96 days for the greater angle-wing, 58-96 days for snowy tree cricket, 67-91 days for the scissor-grinder cicada, 64-94 days for the greenstriped grasshopper, 62-109 days for Linne’s cicada, 72-105 days for the dog day cicada, 81-107 days for the common true katydid, 107-139 days for Allard’s ground cricket, 111-141 days for striped ground cricket, and 113-143 days for Carolina ground cricket).
The number of clear, cold nights seemed high enough in November that they might partly explain the early conclusion of common ground cricket songs this year, especially given the recent study by MacMillan et al. (2012) indicating that there is a metabolic cost to recovering from cold-temperature paralysis. However, I found no significant relationship between last song dates and the number of November days with low temperatures below 33F over 2006-2012 for any of the three species (Spearman’s r values 0.51 for Allard’s ground cricket, -0.39 for striped ground cricket, and 0.33 for Carolina ground cricket). It is interesting, though, that I have seen a few red-legged grasshoppers active a couple weeks after the last ground cricket.
An early December red-legged grasshopper
This bigger insect may have larger fat reserves to draw upon and so extend its season.
September 14, 2012 at 6:25 am (botany, ecology, plant-eating insects)
Tags: Agalinus purpurea, Boltonia latisquama, differential grasshopper, false aster, friary demolition, marsh, Mayslake, Melanoplus differentialis, Melanoplus femurrubrum, old witch grass, Panicum capillare, purple false foxglove, red-legged grasshopper, river bulrush, Scirpus fluviatilis
by Carl Strang
Lately I have been reporting mainly on singing insect researches I have been conducting on vacation time in Indiana and Illinois. When working, though, I have continued my practice of lunchtime preserve monitoring at Mayslake Forest Preserve. The stream corridor marsh still has no standing water.
Dense grasses and river bulrushes have been transpiring all the recent rainfall.
One of the zoned vegetation rings is dominated by old witch grass, which last year was present only in a few small patches.
I have found new species there to add to my preserve lists, all the same.
Purple false foxglove plants have appeared at both the north and south edges of the marsh.
Another addition is Boltonia, the false aster.
Scattered in the dense, coarse, river bulrushes are differential grasshoppers, a relatively large species that likes wet places.
The olive-green color and black herringbone pattern on the femur are distinctive.
Up at the former friary site, the soil now is safely held together by a mix of weeds and fast-growing prairie plants.
The site on August 10
This area has its common grasshopper as well.
These appear to be all red-legged grasshoppers, a smaller and relatively weedy insect species.
I’ll be back to reporting on Mayslake more regularly soon.
October 17, 2011 at 5:58 am (plant-eating insects, singing insects)
Tags: Conocephalus brevipennis, Conocephalus strictus, Mayslake, Melanoplus femurrubrum, red-legged grasshopper, short-winged meadow katydid, straight-lanced meadow katydid, weed
by Carl Strang
Over the past couple months there have been large numbers of grasshoppers at Mayslake Forest Preserve, especially around trail and parking lot edges where mowed lawns come up against a variety of unmowed forbs and grasses. My focus in recent weeks has been on singing insects, but with that research checklist essentially complete for the year I decided to look into those grasshoppers. Perhaps I waited too long, as every hopper I got a good look at last week appeared to belong to the same species. I collected a couple of them and, after a session with references and the microscope, settled on an identification.
Red-legged grasshopper, Melanoplus femurrubrum
As I went through the references and keys I was surprised by the number of similar species and the small features that can separate them. Very close ones often segregate by habitat, however, and red-legged grasshoppers are one of the most abundant, weediest species. Ecologists think of weeds as organisms which reproduce in large numbers and occur in disturbed habitats. Therefore, animals as well as plants can be weedy.
While scrutinizing grasshoppers in the field I also got looks at several small (Conocephalus) meadow katydids. All clearly were short-wingeds, except for one.
The oddest feature on this female is the kink in her ovipositor.
She had an abdomen tip colored like that of a straight-lanced meadow katydid, but the shorter ovipositor and leg striping pattern pointed to short-winged meadow katydid, so I am staying with that more conservative identification.