Changes in Populations of Carolina grasshopper, Dissosteira carolina, at a Barnes Prairie Remnant, Racine Co., WI from 1976- 2023
Carolina grasshoppers are large, broad-winged Caelifera with a high, sharp ridge on the pronotum. Here at Barnes Prairie, they are typically clay-colored, yellowish tan, light brown or grayish; brick red individuals are also sometimes seen. Their distinctive hind wings are black with a yellow border, which give a vague resemblance to a mourning cloak butterfly when in flight. They are strong, sometimes erratic, flyers. Prior to 1976, Carolina grasshoppers (then called Carolina locusts) were prevalent along roadsides, in old fields and by hedgerows, and in scattered remnant tallgrass prairies in southeastern Wisconsin. The populations of this common grasshopper appeared to be stable in my early surveys from 1976 through 2010. In 2012, populations began to decline; this has continued through 2023.
The following is a summary of sightings I made of this common grasshopper during my many trips to Barnes Prairie. In 1976, there were also numerous large orb weavers on the prairie: a few cross orb weavers (European cross orb weaver, European orb weaver), many yellow garden spiders (black and yellow argiope) and banded argiope. There was a significant decline in the populations of these spiders in 2011.
Below is a summary of my observations from various years, beginning in 1976 and ending in 2023. Month, Day and Comments have been left as they were written.
Year, No. of Carolina grasshoppers, Month, Day and Comments
1976, numerous, Sept. 4 along gravel at roadside, and in prairie.
Counted 5 in about eight feet.
1977, many, Aug. 27 hot and humid. Flying Carolina locusts from gravel
where I parked the car, and at almost every footstep I made
into this prairie remnant. Four were counted in European
orb weaver webs, one in a black and yellow argiope web.
1978, many, Sept. 2 A lot of Carolina locusts flying on roadside and
prairie. Several seen on road, also, were dead.
1980, numerous, Aug. 31 Flying grasshoppers numerous, some in orb weaver
webs. Saw one fly into a European cross orb weaver web.
1991, numerous, Sept. 1 cool, windy. Carolina locusts numerous, along with
a lot of other grasshoppers I could not ID.
1996, numerous, Aug. 24 hot. Out with daughter looking at spiders. Largest
prey seen in the numerous orb weaver webs (European
cross orb weaver and black and yellow argiope) were
grasshoppers. Six of 11 could be ID'd as Carolina locusts.
We flushed a lot of them while walking here; good news
for the spiders.
1998, many, Aug. 29 Many Carolina grasshoppers, flying alongside
gravel and in the prairie.
2006, numerous, Aug. 26 great weather for a survey, mid 70s. Numerous
Carolina locusts flying over gravel at roadside, and in
prairie; not counted but thought to be over 40 just at
roadside. Walked 300 feet before entering the prairie.
Numerous locusts in prairie remnant also, along with
monarchs (4) many small moths, not identified, buckeye
(3), and over a dozen cabbage whites.
2010, many, Aug. 28 Temp in 80s, fewer Carolina locusts seen than last
year. The dog is jumping up and occasionally catching
locusts at the gravel roadside. Estimate about 30
grasshoppers in about 200 feet by the gravel.
2012, many, Sept. 1 CL’s (Carolina locusts) flying into cars and hitting
me as I walked from gravel roadside into prairie remnant.
Many in the remnant also. Counted 18 in about 200 feet,
which was less than I’d seen in past years.
2015, few, Aug. 22, late afternoon. Not a lot of Carolina locusts, but
there are also some other grasshopper spp. here.
2017, 8, Late August. Few Carolina locusts, only counted eight. Only
one orb weaver, Eurasian cross, seen, but there are two
worn webs. Few species of other grasshoppers couldn’t get
IDs. Some bottle flies present, two pearl crescents, one
eastern tailed blue, three monarchs and three European
mantises. Many cabbage whites in nearby field.
2018, few, Aug. 24, afternoon, light rain has stopped. A few Carolina
locusts scattered along one mile stretch of grassy degraded
prairie.
2019, 6, Aug. 18 cloudy, afternoon, light rain earlier. CL’s (Carolina
locusts) scattered. Five counted flying or resting on grasses,
ground. Another being dismembered by a European mantis,
on buckthorn.
2021, 1, Sept. 1 One Carolina locust at weedy section of the prairie.
2022, 2, During four late July surveys, no CL’s seen. One CL (Carolina
grasshopper) on August 17, one on Aug. 24.
2023, 3, August 18, 26. Two Carolina locusts on the 18th, one on the
26th. During surveys in earlier August, none seen.
Carolina grasshoppers were not the only insects to decline in numbers over these years. Reductions in the numbers of many other insects have also occurred. Native orb-weaving spider populations here have also greatly declined.
Possible causes for the decrease in numbers of Carolina locusts:
Increase in the numbers of European mantis on this prairie remnant. The first mantis was seen here was in 2012. Three were found in August 2017. Eight were found in Late August of 2023, along an 800-foot stretch of the prairie. In 2017, adults and children were seen releasing mantises onto this prairie.
The climate has been changing here; we now have late, cold springs, drier summers, warmer and wetter falls and winters. Some winters have little snow.
Increase in the number of invasive shrubs, especially honeysuckle and buckthorn.
Changes in herbaceous vegetation; patches of invasive thistles and reed canary grass have greatly increased, and many prairie insects and spiders are not found in these areas.
The number of bald-faced hornets has not increased in this area, however; there are German yellowjacket hornets, flesh flies, tachinid flies and other predatory insects in the area. Population dynamics of these insects have not been recorded during the surveys.
Glyphosates have been used on nearby properties since the late 1970s. They are not used on the prairie, but may have drifted onto this area.
So far as I have been able to find out, there is no known use nearby of neonicotinoids.
Other unknown factors may also be at play here.
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