Pestology Blog
Crime Solving Bed Bugs, Resilient Roof Rats, and AI Cockroaches
Fairfax, VA – April 1, 2025
In this episode, the NPMA team discusses new research on how bed bugs could solve crimes, ways to improve bed bug control, and the use of artificial intelligence to track cockroaches. We're joined by special guest Erin Richardson of All-American Pest Control!
Featured Article Summaries
Crime Solving Bed Bugs
Bed Bugs, Cimex lectularius: Undercover Agents in Forensic Investigations
While we’re likely not getting a Law and Order: ENTO spin-off anytime soon, we may have new witnesses to put up on the stand: bed bugs.
As we all know, bed bugs are hematophagous, meaning that they feed on blood. Bed bugs feed on blood throughout their lifespans, and stay close to their source of food. This is makes bed bugs unique, as they are one of the only species that feeds on blood and are relatively stationary, unlike other blood feeders such as mosquitoes or triatomine bugs. Therefore, with these life traits, they have the untapped potential to become one of the most important parts of any crime: tiny witnesses.
This paper focused on the potential use of bed bugs in forensic science. Specifically, the researchers examined whether human DNA could be successfully extracted from bed bugs, and whether that blood could be used for forensic testing to determine who may have been at the same crime scene with those bed bugs.
Bed bugs were given 30 minutes to feed on either male-only human blood, or a 1:1 ratio of female to male blood. The bed bugs were then collected at 12 hour intervals up to 4.5 days later. The researchers then assessed whether they could detect human blood from these harvested bed bugs. The researchers were able to detect human blood in these bed bugs for up to 96 hours post-feeding (or 4 days later) in the combined blood, and a full 4.5 days later for the bed bugs that fed on just the male blood. Therefore, with this test, they could at least determine if a human was on the scene of the crime (and the bed bugs fed on them) up to 4.5 days later.
Moving forward, the researchers decided to examine if this blood that was detected was still a viable option for DNA identification of a suspect using a means called Y-STR profiles. STRs stands for short tandem repeats, which are DNA sequences that repeat in a row, but differ between individuals, which makes them perfect for DNA identification. Y-STR profiles are specifically looking at those short tandem repeats on the Y-chromosome, which only males possess. Therefore, the researchers were specifically looking at whether they could viably use blood extracted from bed bugs to make a positive identification for a male suspect. Identification of female suspects is currently not on the table, as the digestion process in the bed bugs quickly degrades the potential sources of female DNA.
Nevertheless, the researchers were able to build complete Y-STR profiles from the bed bugs up to 60 hours post feeding, so up to 2.5 days later. This means that they were able to generate a profile that could not only positively identify a suspect, but could also eliminate potential suspects as well. Understandably, due to the bed bug digestion process, the researchers found that the DNA in the blood degraded in the post-60 hour window, which made the DNA unusable for analysis.
While this study warrants further research, such as field trials, more diverse blood donors, and a larger sample size, it highlights that we are perhaps ignoring an important witness to crime scenes: the humble bed bug. This study truly emphasizes how intricate our relationships can be with the pests that we are often charged with eliminating. From a simple bed bug feeding to the witness chair, bed bugs might just be the new means of identifying suspects in serious crimes
Article by Laura Rosenwald, BCE
References
Meiklejohn, Kelly & Schal, Coby & Lodhi, Khalid. (2024). Bed bugs, Cimex lectularius: Undercover agents in forensic investigations. Journal of forensic sciences. 70. 10.1111/1556-4029.15638.
Roof Rat Behavior
Behavior and Activity of Commensal Roof Rats around Rodenticide Bait Stations in Southern California, USA
Anyone can cook! This is the motto from ratatouille meaning that anyone can do anything they set their mind to. Let’s take this a bit of a different route. Let’s ask if “anyone can bait!” is true.
This study looked at the behaviors of roof rats around bait stations. In contrast to the sophisticated culinary endeavors depicted in ratatouille, real roof rats are notorious for their destructive behavior. Roof rats, Rattus rattus, are an invasive species of rodent that is common throughout the US, especially closer to coastal areas. These are harmful for a variety of reasons. They can be a threat to native wildlife and they are also known to vector diseases to humans as they live in close proximity to mankind. They pollute food supplies, and cause damage to property but yet relatively little is known about their behavior.
In particular this research focused on southern California. In urban areas, these rats are largely managed by rodenticide bait stations. The general idea of these bait stations here being that a rodent comes around, finds the bait, and eats it. These tamper resistant bait stations are designed to prevent humans and other animals from coming into contact with the baits, and are only able to be opened by a special key. Depending on the type of rodenticide, a rodent may need to feed only once or several times. For baits that need to be fed on multiple times, it becomes imperative that the rodents find a bait station more than once. Even for the one-time feed baits, we still need to make sure the bait station is appealing to the rodents and that they are actually visiting it. A bait station may not be appealing if a rat has access to other foods.
The researchers here looked at how the bait station design, presence of supplemental baits, or addition of scent lures would affect rat behavior around the station. They used digital game cameras to monitor the bait stations remotely their goal was to observe the time to discovery, entry, bait consumption and general nightly activity of the rats. In addition to observing the behavior, they looked at the landscape of the sites such as vegetation levels, other animal presence, and other pest management present.
Trial 1 of the experiment looked at three station designs to see how that affected behavior. They used one that looked like a rock (Fig. 1), Ez-secured (one of the classic rounded square type)(Fig. 2), and big snap e which is a long skinny style station (Fig. 3). All of these are commonly used by pmps, the rock design was expected to affect behavior as that is meant to look like a landscape feature.
They detected roof rats in 33/36 yards and in those yards, bait stations were discovered by the rats about 65% of the time. Ultimately the design of the bait station didn’t make a significant difference, this conflicts some in-lab findings previously but it seems that in the real world in these tested conditions, it didn’t matter.
Of this percentage of stations discovered of any type, far fewer actually went in, averaging around 31% of the total. They also measured the average hours since deployment it took for them to go in which was somewhere in the realm of 6-12 days so nothing immediately. Proving the point that rats wont immediately go for a bait station, neophobia may be a factor.
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| Rock Bait Station | EZ-Secured Bait Station | Big Snap E Bait Station |
Another part of the testing was whether supplemental scent lures would increase bait station activity and it was not found to have any significant effect on it. This may be since the scent lures were not actual food.
Trial 2 was adding supplemental baits. This lead to the most significant finding of this research. The use of non-toxic supplemental lures was found to increase interest in the bait station. Once they are interested in the bait station then they come back to get the actual bait and it begins to work. Rats can be afraid of new things but luring them in with a similar bait outside the station can entice them to enter and then hopefully consume the active ingredient baits inside. This is comparable to a pre-baiting technique.
And in the words of Remy’s father, “Food is fuel, you get picky about what you put in your tank, you’re gonna die. Now shut up and eat your garbage.”
So, the moral of the story is that with the right training and creativity, any PMP can bait
Article by Ellie Sanders, BCE
References
Bosarge, Miles and Stapp, Paul and Quinn, Niamh, Behavior and Activity of Commensal Roof Rats Around Rodenticide Bait Stations in Southern California, USA. Available at SSRN: https://ssrn.com/abstract=5131140 or http://dx.doi.org/10.2139/ssrn.5131140
Photo Credits:
- https://www.belllabs.com/products/us/pest-control/protecta-evo-landscape/
- https://veseris.com/default/catalog/product/view/id/357800/s/ez-secured-the-original-weighted-bait-station/category/11492/
- https://www.kness.com/pest-control-products/rat-traps/Big-Snap-E-Cover/
AI Cockroach Tracking
Measuring the Effect of RFID and Marker Recognition Tags on Cockroach (Blattodea: Blaberidae) Behavior Using Ai-aided Tracking
Understanding insect behavior is a critical component of pest management. This is especially true for cockroaches. Knowing when they forage for food, where they prefer to hide, and what their reproductive strategies are all serve as the foundation of every control program. Much of the knowledge we have of cockroach behavior has come from careful observation and intentionally designed experiments that allow us to visually monitor activity and log data.
One thing that decades of behavioral observation have taught us is that cockroaches are thigmotatic, meaning they prefer to hide in tight spaces like cracks and crevices. Understanding this behavior has served us well over the years as a means of helping to identify ideal harborage sites. What cockroaches do behind the shadows in these harborage sites, however, is mostly a mystery. But thanks to advances Radio Frequency Identification technology (RFID for short), that may all change.
Radio frequency identification is a system that uses radio waves to identify and track objects. It works by attaching a unique tag to an object that can send location data to a corresponding receiver. This technology has been used successfully in recent years to study many different animals, offering an efficient and non-intrusive way to monitor them without human interference. As this technology has progressed, RFID tags have gotten smaller and the algorithms used to interpret movement data have gotten more advanced, making this an important tool for invertebrate research.
A requirement for RFID tracking to succeed is that the installation of the tags doesn’t influence the insect’s behavior. And, the tracking models used to interpret movement need to be precise enough to accurately detect and generate movement pathways for something as small as a cockroach. Thanks to recent advances in RFID technology, there are now several different tagging and open-sourced tracking software options that make this option more viable and affordable than ever before. All we have to do is test them out. And that’s exactly what researchers Callum McLean & David Fisher did.
Activity for all experiments was measured using an automated tracking software (DeepLabCut version 2.3.9), used to quantify three animal behaviors: 1) average speed, 2) exploration (sum of total distance traveled), and 3) total number of walks which the researchers defined as any period of 1s or longer of continuous movement.
After analyzing the data, Callum and Fisher found no statistically significant differences between RFID tagged and untagged cockroaches in any of the behaviors measured. They did, however, observe that cockroaches affixed with label markers had significantly higher values for all three behavioral metrics vs RFID tagged cockroaches. The authors theorized that the increased activity of label-marked cockroaches could be a sign of stress, suggesting that RFID tagging may be a preferred method if precise movement tracking is needed. Regardless, these findings support that RFID technology could be a viable method for marking and tracking cockroach behavior without significant interference.
While these findings are encouraging, it’s important to note that this study was only conducted on the Argentinean woods roach, a relatively large cockroach compared to other pest species, and that similar tests should be run on smaller species to assess outcomes. For size comparison, the Argentiean woods roach averages about 40-45 mm in length, while the German cockroach, a globally impactful pest species, measures only about 13-16 mm in length. The smaller bodied German cockroaches may present a unique set of issues under the same experimental conditions. Therefore, further study is still required to get a full picture of what RFID technology may mean for tracking cockroaches in the dark unseen spaces they like to hide. But, the future for this technology looks very promising!
Article by Mike Bentley, PhD, BCE
References
Callum J McLean, David N Fisher, Measuring the effect of RFID and marker recognition tags on cockroach (Blattodea: Blaberidae) behavior using AI-aided tracking, Journal of Insect Science, Volume 25, Issue 1, January 2025, 5, https://doi.org/10.1093/jisesa/ieaf002
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