Hi, Haley again!! It’s been an exciting couple of weeks- I’ve become more familiar with mosquitoes than I ever thought I would, learned a TON more Matlab, and even got a few recordings!! My work recently has focused on perfecting the methodology needed to successfully tether a mosquito in a position mimicking their natural free flight position; the tricky thing is to assure it is tethered with its wings free to flap, as my recordings will focus on hearing that irritating noise generated by a mosquito’s wing beat patterns.
After much tedious practice, I finally figured out a way to anesthetize these little guys using ice water and tether them using a very thin insect pin with a tiny amount of insect wax. The goal was to assure that they were suspended in a secure position to reduce the chance of them getting loose and flying straight for my face (though that has happened a couple of times, so now whenever there is a stray fuzzy in the air around me, I duck for cover…little bit paranoid…) Below are some creepy cool pictures of my little friends tethered that I was able to capture using a low-intensity microscope.
I am fortunate enough to be able to purchase these mosquitoes (Aedes Agypti) from a research laboratory that specializes in bioassays of insect control agents for lab testing. So, getting them has been easy… but maintaining them in a lab setting has proven to be very difficult. Once I receive my little ones in the mail, they usually live about 3-4 days, so once they are no longer viable for testing, and as I wait for my next shipment, you can find me frantically running around Nicholas Arboretum attempting to catch some wild-type mosquitoes. I’ve gotten some pretty weird stares and even weirder questions when I lurk in bushes near the Huron River trying to catch my prey, but hey, anything for science!!!!
Five seconds after this picture was taken, I fell into a pond.
Although it sounds so exciting and desirable, running around the Arboretum with mosquito nets actually isn’t the best part of my project this summer! We’re just getting to the good stuff!
Once I got a few mosquitoes tethered and ready to go, I was able to start recording some of the awesome sounds these guys produce in free flight. That pesky buzz of a nearby mosquito is actually a love signal, a sound they produce and adjust in order to mate with one another! However, before recording these adjustments in their wing beat frequencies when placed within earshot of each other, I needed to record individual mosquitoes to build up my recording database that will help me clearly show the difference in base frequencies between male and female mosquitoes. Research has shown that females have a base frequency of about 400 Hz, while males are around 600 Hz, so the next stage in my research was to prove this phenomenon via data collection and analysis.
This preliminary data recording stage is still ongoing, but nearing its transition into recording mating pairs, as the data I have collected thus far is pretty spot on with the research! As with any scientific study, there will always be factors that make perfectly reproducing results from another research study challenging, so my goal was to get as close as possible, and I did!
Here are some samples…
When I was ready to start collecting data, I first focused on recording the wing beat frequencies of as many male mosquitoes as I could before nearing the end of their lifecycle. Thus far, I have obtained significant data from 9 male mosquitoes, where their base frequency was in range to what I anticipated (though slightly higher than the published data) and their harmonics are exactly as expected. Below shows one spectrogram of a male recording, as well as a graph showing the frequency distribution of all 9 male recordings during free flight.
Next, I moved my focus onto recording the female mosquitoes in free flight. These little ones were much harder to tether, for a number of reasons- their size, they didn’t respond as well to the cold water anesthesia so they kept waking up during pinning, and the insect wax didn’t solidify on their abdomen as easily as the males. All I have to say is if you see a million mosquitoes flying happily in our makerspace, don’t look at me!!!!
After overcoming that challenge, I was able to successfully obtain recordings from 7 female mosquitoes, though I tethered much more than that and for an unknown reason, many of the females in this batch wouldn’t beat their wings. The 7 good recordings I got are shown on the graph below in addition to one female spectrogram recording, with an identical format to the male distribution graph above.
Being super happy with this data, I wanted to take the analysis one step further to connect my findings with that of Ron Hoy, the professor at Cornell and mastermind behind all of this research. A figure that reappears throughout his research (pictured below) shows a clear spectrogram depicting the harmonic stack of sound clips from both male and female recording sessions.
My goal was to reproduce this figure with the data I collected thus far in my research. That figure is shown below, with a little extra color coding thanks to my OCD (red = female, blue = male)!
The rest of my research plan consists of obtaining more individual recordings to clean up the figure above, and then record mating pair interactions! All of these recordings will be conducted in a sound-proof box that I created, with a lid that has a laser cut track removed to allow for me to manually move the male mosquito in and out of the females hearing range throughout the duration of the recording. This procedure is to clearly reveal the altering of flight tones when the mating process begins.
Stay tuned to see where the next stage of my project leads! I can’t wait!