Hiking the extensive trail system that connects Red Rocks Park with Section 16, west of Colorado Springs, one encounters an impressive array of ripple-marked sandstones, a beach back in the Mesozoic, now dipping at almost 90°. The so-called “White Acres Trail” should have been named “Ripple Mark Trail.” The steep east-facing slope of the hogback seems to be Niabrara sandstone, but is backed on the west by Dakota SS, both of which form hogbacks. But how about these classic ripple marks?
Like everything else in 2020, mothing wasn’t great for me in the Pikes Peak Region. I wasn’t able to distinguish additional species from the few moth photos posted to Arthropods Colorado and Wyoming, and I’m sure I missed some. But on a single trip up Bear Creek in early August I discovered two species of moths new to my database. The first (above) is probably Hellinsia homodactylus, a Pterophorid, and the second (below) is Glyphipteryx montisella, a Gelechiid, nectaring with a few tiny flower beetles.
(This is the last in a series on this subject. Earlier graphs are replaced herein).
Modern research shows a precipitous decline in insect numbers worldwide in response to climate change and agricultural practices. For the frightening details, see the Guardian’s overview of the major reports (https://www.theguardian.com/environment/2019/feb/10/plummeting-insect-numbers-threaten-collapse-of-nature). The current study adds data to this general question, and includes 232 visits to the site (Bear Creek) across 21 sampling years from 1998 through 2020.
Observations were made along a haphazard transect (a road) about 1 km long from the caretaker’s house at the parking lot to the Specimen Rock trailhead and about 150 m beyond. The average hike spanned between 1½ and 2 hours, and the sampling time was recorded in every case.
Forty-six species were chosen from the 125 that have been found at the site. These species are generally widespread, found almost every year, and do not tend to produce population explosions. Formerly rare species such as Amblyscirtes eos, Brephidium exile, Junonia coenia, and Adelpha eulalia were excluded because they are moving into the region in numbers as of the last five to seven years. These, of course, show increasing numbers.
Butterfly abundances are recorded in terms of numbers observed per hour, and the average for each year is recorded for graphing purposes. Thus, the graphs show the annual average abundances as a function of years. Slopes are plotted for each data set, and although none of the effects approach linear, the slopes are shown to address the general trends across the years. The broad scatter is due to many factors, including climatic and weather conditions, experimental error, and the natural fluctuations of populations.
Most butterfly species in the American West are highly adaptable to wide swings in weather conditions, making them resilient against changes in climate. Regional land use is generally innocuous in terms of butterfly dynamics, neither encouraging nor discouraging population development. In comparison with agricultural regions, Pikes Peak has generally escaped the deleterious affects of pesticides, herbicides, and monocultural practices. Nevertheless, populations are beginning to show a slow decline across all butterfly families, the overall average slope being y = – 0.028x, suggesting a very slight decline in numbers across the 20 years.
Disturbance at the site has been minimal and unchanged until the spring of 2020, when a mitigation effort was initiated to assist in the management of the protected green-backed cutthroat trout. The changes affected mainly the upper south slope, destroying a significant stand of Monarda fistulosa, a mint, the flowers of which are highly attractive to butterflies, especially some members of the family Hesperiidae and the Nymphalid genus Speyeria. The numbers of these groups were not affected in 2020, probably due to the numerous other nectar sources available. Graphic results follow.
Mean slope : y = – 0.0292x
Mean slope : y = – 0.0124x
Mean slope: y = – 0.046x
Mean slope: y = – 0.077x
Mean slope: y = – o.oo64x
The interpretation of these data is difficult, of course, but the general trend is that butterfly populations are stable across this period. Out of the 46 species studied, 32 (70%) show negative trends. The very slight downward slope is suggestive and holds for every group. Other studies (posts below) show a loss of total numbers of butterflies, and a loss of species diversity across the same time period.
This is a summary of my 37 years of data on the butterflies of the Pikes Peak Region. The following graphs show trends in abundances as measured by butterflies observed per hour afield. Each data point is a record of the number of butterflies observed per hour of observation time. First, the whole data set for the Pikes Peak Region, with tons of scatter:
This shows an almost flat line, but slightly increasing (from 69/h to 78/h). But when I restrict the data to only Bear Creek, where I have spent most of my time, we find:a negative slope (from 87/h to 80/h). And when graphed according to the average number per hour for each year, we get:a more negative slope (from 102/h down to 79/h). This is surprising to me, as 11 years at an Austin Bluffs site shows no such decline:even when plotted according to annual averages:I also created box and whisker plots for the numbers of butterflies per hour for each summer month in Bear Creek!
In sum, butterfly numbers appear generally stable in this region, but further study is always needed as we enter a hotter earth with more fires.
Theme 113, with a flute and trombone.
My new butterfly record is of Zizula cyna, a tiny subtropical blue that should not be here. It was taken near the Section 16 Trail, as the label says. I will go back this summer to see if it might persist in that environment. It is not particularly unusual to find stray subtropical butterflies in Colorado, but one this tiny is hard to imagine. Perhaps it came on a car with travelers, but if so, it flew hundreds of yards to the locality in which I found it. So, maybe…
A bit late, but…
These are the moths that I recorded as new to the Pikes Peak Region in 2019. Many thanks to Eric Eaton, Aaron Driscoll, Zach Vogel, and Van Truan for keeping a sharp eye out. Keep looking in 2020!
Addendum: Here are species that I didn’t have on pins.
These are 164 of the 206 species that have been recorded in El Paso County. Many of the rest are rare strays, but we may see them more commonly as the climate warms. Adelpha bredowi, for example, used to be a rare stray, but it shows up almost every year now in the region. I will continue to add to this set as new photos come in from the Pikes Peak Region, with your permission, of course.
Here are the results from two sweep samples of insects taken ten years apart at exactly the same location on the Section 16 Trail west of Colorado Springs. In both cases, 100 sweeps were made. In this area, which is relatively undisturbed in terms of regular application of pesticides, herbicides, and insecticides, total numbers of insects seem very similar after ten years. T-Tests, both one-tailed and two-tailed, show p values that do not suggest significance. I chose a date one week later in 2019, as the season appears a bit behind average in terms of butterfly emergence dates.
The Wonder and the Challenge…
The following moths, discovered by several workers in the region, are new to my database of species in the Pikes Peak Region. Thanks to Eric Eaton, Aaron Driscoll, Zach Vogel, and Van Truan for posting photos of some of these. The ones without initials are from my collection, mainly from the bioblitz at Corral Bluffs in September. At that site, on one night, I took ten species new to the region.
Thirty-six new species found in the area. Keep going, guys. This is fun.