The western conifer-seed bug (Leptoglossus occidentalis) is an invasive, plant-eating pest that has arrived in South America in recent years. Due to its resemblance to kissing bugs and its propensity to overwinter in homes, entomologists in Chile have seen a rise in public alarm. While kissing bugs are known to carry the pathogen that causes Chagas disease, the western conifer-seed bug is not a disease vector and has only rarely been reported to bite humans. (Photo credit: Dawn Dailey O’Brien, Cornell University, Bugwood.org)

By Eduardo Faundez, Ph.D.

This week, my colleagues Mariom Carvajal and Javier Villablanca and I published a paper in the Journal of Medical Entomology titled “Alien Invasion: The Case of the Western Conifer-Seed Bug (Heteroptera: Coreidae) in Chile, Overreaction, and Misidentifications.”

Eduardo Faundez, Ph.D.

We chose this title because of the unusual situation that has happened in Chile with this alien species and an unfounded panic caused by its invasion and several misidentifications.

The western conifer-seed bug (Leptoglossus occidentalis, hereafter referred to as WCSB) is a coreid bug that feeds on conifers. The species is native to western United States and has become invasive in the Eastern part of the U.S., several European and Asian countries, and most recently in South America. It was first detected in Chile during 2017. After that, it rapidly spread across the country. Currently it has also reached Argentina, where our colleagues led by Diego Caripintero, Ph.D., at the Museo Argentino de Ciencias Naturales are studying its situation there.

WCSB is considered a pest, as it attacks some economically important conifers. Moreover, it aggregates to hibernate inside homes and produces some structural damages, especially to plumbing materials. Also, although it is a phytophagous insect (i.e., it feeds on plants), it has been recorded biting humans adventitiously.

However, none of these has been the main problem in Chile. As it is a new invader from the Northern Hemisphere, it looks unusual to Chilean inhabitants, who have found WCSB to bear a resemblance to kissing bugs (Triatominae), known for their ability transmit Chagas disease. Chile is within the endemic Chagas zone; therefore, having several “kissing bugs” near homes and overwintering fueled the alarms.

A case of look-alikes: Leptoglossus occidentalis, the western conifer-seed bug (A), bears a resemblance to kissing bugs Triatoma infestans (B) and Mepraia gajardoi (C). The former is a plant eater, harmless to humans, while the latter two are vectors of the pathogen that causes Chagas disease. (Image originally published in Faundez et al 2019, Journal of Medical Entomology)

As we report in our study, over nearly 2 years we received 74 alleged kissing bugs for identification, of which 85 percent were the western conifer-seed bug.

Researchers in Chile received 74 alleged kissing bug specimens from members of the public between January 2018 and May 2019. Of those, 85 percent were in fact western conifer-seed bugs (Leptoglossus occidentalis). (Figure originally published in Faundez et al 2019, Journal of Medical Entomology)

A case of look-alikes: Leptoglossus occidentalis, the western conifer-seed bug (A), bears a resemblance to kissing bugs Triatoma infestans (B) and Mepraia gajardoi (C, female; and D, male). The western conifer-seed bug is a plant eater, harmless to humans, while kissing bugs are vectors of the pathogen that causes Chagas disease. (Image originally published in Faundez et al 2019, Journal of Medical Entomology)

So, why this overreaction is important? First of all, WCSB had become very common in homes, especially as ornamental pine trees are common across Chile. So, this increase directly impacts our health system, as people are asking about Chagas disease when it is totally unnecessary. Furthermore, as this is an introduced insect from another hemisphere, our health professionals are not trained to accurately distinguish these bugs, nor are many entomologists, if they do not work closely with Heteroptera. Finally, the generalized panic situation causes an overuse of pesticides in urban areas, with effects on local fauna and human health if not applied correctly.

What we propose as solution in our paper is to provide identification tools that are easy to use for any professional in need, and also to create educational programs to help people recognize this new inhabitant and avoid overreactions in case of bites.

This is not the first case in which a true bug has caused panic. Maybe the most iconic is the meme that appears on social media over and over with an image of a Belostomatid bug and a hand with multiple holes meant to cause trypophobia. The image is usually accompanied with sensationalist texts telling that the bite of the bug is the responsible for the problem with the hand. Like this, several bugs like the brown marmorated stink bug have been used in infographics of kissing bugs, causing more confusion.

Although our case occurred in Chile, the same thing may happen in several places where the WCSB invades.  However, we don’t blame Chilean people for getting scared by this bug. Years ago, the 22nd episode (“F. emasculata”) of the second season of The X-Files featured a fictional bug, Faciphaga emasculata, and the insect chosen to be the stand-in for the adult stage of the fictional bug on screen was—I am almost certain—a western conifer-seed bug.

Eduardo I. Faúndez, Ph.D., is an entomologist at the Instituto de la Patagonia, University of Magallanes, in Punta Arenas, Chile. His major research areas are systematics of the Heteroptera and medical zoology. Email: ed.faundez@gmail.com.