On average, I see 2 – 3 new, non-native insect species show up in Wisconsin every year through my work at the UW Insect Diagnostic Lab (3 so far in 2021!). I’ve mentioned this in previous blog posts, but humans make excellent accomplices in moving species from one spot to another on the globe. This last spring, I saw one of the most interesting cases of my career which highlights this point exactly.
Like any good globetrotting adventure, this story involved a rugged, adventurous mode of travel—a Jeep. This particular Jeep had been imported in late 2020 and after a period of time in the eastern US, it eventually wound up in a small town in central Wisconsin. Unbeknownst to the owner of the vehicle, this Jeep also contained unexpected insect stowaways.
These insects managed to survive for months sheltered within the Jeep and would become active when the vehicle was in use—unexpectedly wandering out of nooks and crannies, much to the displeasure of the driver. Obviously, this isn’t something a new car owner wants to see, so a pest control professional was consulted about the insects and they got in touch with me at the UW Insect Diagnostic Lab to figure out what the specimens were. In the initial conversation, the mystery insects had been described as “stink bugs” and I figured that overwintering nuisance insects like the brown marmorated stink bug might have been involved. The photos, however, hinted at something far more puzzling.
By this point, I had been running the UW Insect Diagnostic Lab for six years and hadn’t seen anything quite like the insect in the photo. I requested a sample to get to the bottom of this mystery under the microscope. I handle so many cases at the diagnostic lab (~2,500 annually), that I can generally identify most specimens to family (or perhaps even genus or species-level) with a quick peek. In this case I was utterly perplexed, meaning I had to run it through a general family-level taxonomic key for the true bugs (Order Hemiptera). In Borror and DeLong’s Introduction to the Study of Insects the specimens keyed out to the Family Heterograstridae.
An asterisk is always a surprise when you encounter it in a taxonomic key. It generally means one of two things: you either took a “wrong turn” in the decision-making process (and misidentified the specimen) or it’s something rare or highly unusual. Something seemed amiss, so I consulted a few other keys to further confirm the Family Heterogastridae. In North America there’s only a single genus (Heterogaster) from this family and three species known from the west coast of the US. The specimens in my possession looked markedly different. Because the Family Heterogastridae is mostly a footnote in the western hemisphere, it’s hard to find information on this group of insects.
This is why geographic clues can be so important in diagnostics and why I request this information with every sample at the UW Insect Diagnostic Lab. Knowing where a specimen was collected and/or originated helps tremendously in learning more about it. Through follow-up conversations, I learned that the Jeep was manufactured in and imported from Melfi, Italy—meaning there was a good chance I was looking in the completely wrong hemisphere for the information needed to identify it.
This led to many evenings of armchair sleuthing. During this process, I’d like to imagine myself as Jason Bourne tracking down members of an international conspiracy while a suspenseful soundtrack blared in the background, but in reality I was mostly just locating pdfs of scientific papers and using Google Translate. Such work could have taken months or even years a few decades ago, but was now possible in the matter of a week or two.
Thanks to Interlibrary Loan and other online resources, I tracked down manuscripts from a half-dozen European and Middle Eastern countries in multiple languages and spent hours pouring over posts on Italian and French insect forums looking for clues. I finally found my answer in a scanned pdf version of Jean Péricart’s Hémiptères Lygaeidae euro-méditerranéens, vol. 1., which identified the specimens as Platyplax inermis—a species associated with Salvia spp. plants in the Mediterranean region.
Having finally identified the stowaway insects and their origin, my work was mostly done at that point. The species happened to be on the USDA-APHIS regulated plant pest list (technically, the entire family Heterogastridae is listed), so I reached out to colleagues at the USDA-APHIS office in Madison to hand off the case. Specimens were sent off to an APHIS field office in Chicago and then off to the Smithsonian for further confirmation, a few specimens are also being deposited in the Wisconsin Insect Research Collection.
While most cases at the UW Insect Diagnostic Lab aren’t anywhere near this exciting, even insect diagnosticians get to live vicariously every once in a while.