By Sharman Apt Russell
A few years ago, as an enthusiastic citizen scientist, I was tasked by entomologists and tiger beetle experts David Pearson and Barry Knisley (co-authors of A Field Guide to the Tiger Beetles of the United States and Canada, among other books) to fill in a small blank spot on the map of tiger beetles — namely, the larval biology of the western red-bellied tiger beetle (Cicindela sedecimpunctata). This involved collecting the western red-bellied tiger beetle along the banks of the Gila River in southwestern New Mexico, confining these manic and fierce type-A predators to terrariums, watching them mate and mate and mate, and emailing my mentors with delight when the females decided to oviposit.
“My” eggs hatched, and the larvae dutifully made their burrows, from which they would peer out, waiting for me to feed them dissected mini-mealworms. I was the first to see — or at least to document — this species’ first and second instars, and I sent specimens to Barry Knisley to describe for the scientific record. He and David Pearson had tried rearing this tiger beetle before, without luck, except for one lone third instar.
Getting scientific descriptions of these instars was all well and good. But the real larval question was, where and in what kind of habitat do the females lay their eggs? The real point was to find these larval burrows in the wild, which proved surprisingly hard to do.
Western red-bellied tiger beetles are active in the summer, the adults congregating around water sources such as ponds, ditches, and river banks in Arizona and New Mexico in early- to mid-June — before the monsoonal rains — and then dispersing to higher elevations in late July and August.
Just before my second summer of watching these tiger beetles, Barry Knisley emailed me. He wondered if knowing when these insects oviposited might help tell us where they did so.
“One aspect of resolving the puzzle of sedec. oviposition would be to examine the ovaries of adult females at periodic intervals through the season,” he wrote. “If they are not ovipositing during their early-season activity, but rather are doing it after they disperse at the end of the season, we would not expect to find mature eggs in the female ovaries until late in the season. Dissecting females is not too difficult with a binocular scope, though not the most pleasant thing.”
To tell you the truth, I was flattered that Barry would think me remotely competent at dissecting the female ovaries of insects less than 10 millimeters long. In fact, I had some trying times at the microscope, which in no way resembled the aplomb of all those CSI shows I have watched on television. But in the end, the ovary dissections I conducted that momentous summer season revealed large eggs — seemingly ready for oviposition — in western red-bellied tiger beetle females only a month after the adults appeared in early June. Moreover, eggs continued to be seen in different stages — small, medium, and large — throughout the season.
Of course, this was not at all what we had predicted. Our hypothesis was proven completely wrong, which was another wonderful moment in science for both Barry and me.
With this new information, Barry and I now guess that individual females leave the water’s edge to deposit eggs when the eggs are fertilized and matured. Then the females return to the river bank to continue feeding and mating. This would be similar to the aridland tiger beetle (Cicindela marutha), which travels at night as far as half a mile from her feeding area to lay her eggs in nearby sand dunes.
Perhaps the western red-bellied tiger beetle does something similar, choosing a more loamy mix of earth. My captive females, at least, did not lay eggs in terrariums of river sand, but instead preferred dirt taken from nearby grassy hills. Partly for this reason, but mainly because of extreme and erratic flooding along the bank and the lack of observed burrows there, we do not think this beetle oviposits in the area of adult activity.
The Gila River, close to my house, runs through 3 million acres of national forest. If I cover a million acres a year, then I am looking at a three-year study. Like some of my other citizen science projects — monitoring archaeological sites for the New Mexico Site Steward Program, and inventorying possible new wilderness areas for the New Mexico Wilderness Alliance — it’s a great excuse to get outside and marvel at the beauty of the world.
Sharman Apt Russell lives in the Gila Valley of southwestern New Mexico and teaches writing at Western New Mexico University and Antioch University in Los Angeles. Her books related to entomology include Diary of a Citizen Scientist: Chasing Tiger Beetles and Other New Ways of Engaging the World (Oregon State University Press, 2014) and An Obsession with Butterflies: Our Long Love Affair with a Singular Insect (Basic Books, 2005). Her work has been widely anthologized and translated into more than ten languages. For more information, please go to her website and consider signing up for her infrequent newsletters at www.sharmanaptrussell.com.