Introduction/Theory
For my mosquito experiment, I am testing how different kinds of bait affect the number of oviposition in my trap. Different mosquito species are attracted to different habitats, natural or artificial, some of which have been changing due to climate change. Mosquitoes are the most dangerous animal in the world because of their disease transmitting abilities, so understanding their oviposition instincts could be crucial in order to prevent further spreading of dangerous diseases such as the dengue virus, malaria, or the zika virus.
Variables
Independent variable- the type of bait (citronella, orange essence, cider) Dependent variable- the number of mosquito larvae/eggs found in the traps. (+species) Controlled variables...
1. General Location of the Traps- all the traps were set up in my backyard, where the climatic, and environmental conditions are the same. If this was not controlled, it could cause systematic error due to studies having shown that different temperatures do affect the oviposition of certain mosquito species.
2. The additives in the traps (rocks, branches) - all traps were made to have the same number of rocks, branches and pine cones. This was done to ensure consistency in the available places for mosquitoes to lay their eggs. Certain species of mosquitoes lay their eggs on the branches, so keeping this constant is important to ensure the validity of the experiment.
3. The volume of water- all traps were set up with 1L of water. Some mosquitoes do prefer different volumes of water for ovipositions, so it's important to keep this variable controlled to reduce its affect on mosquito oviposition and increase the validity of the method.
Hypothesis
The bait that is predicted to attract the greatest number of mosquito oviposition is the cider.
I came across an article in CBS which said that a study conducted by some Japanese researchers which showed that drinking a beer made you more susceptible to mosquito bites. Therefore, this type of drink is clearly attractive to mosquitoes, so as a kind of bait it can be assumed to be the most attractive out of the three.
https://www.cbsnews.com/news/beer-and-other-reasons-zika-mosquitoes-may-want-to-bite-you/
Method
1. Six containers were collected. 1L of water was measured using a measuring cup and poured into each of the containers.
2. One rock, 3 tree branches, and one pine cone was added to each of the six traps.
3. The first type of bait, citronella, was added to the first two containers. 3 drops of the bait was added as it is very strong.
4. Step 3 was repeated twice more for the orange essence and for the cider.
5. The traps were set out in the backyard and the results were collected the following Sunday.
6. The number of mosquito larvae and eggs were counted every following Sunday. Additionally after checking for mosquitoes, 3 more drops of each bait was added to the trap, and depending on the necessity, some more water as well.
Trap 1: Citronelle (repellant bait)
We always used to light citronella candles during the summer, so I wanted my one of my qualitative increments of bait to be citronella to test the accuracy and efficiency of its natural mosquito repellant abilities. I don't believe this trap while harbor many mosquito larvae, but I'm curious to see if my hypothesis holds true. An article published in May 2022 dissuades people from buying citronella for mosquito repellant purposes. Apparently, the chemical receptors that mosquitoes have can be blocked by certain essential oils such as this one, but there is no guarantee that it will work effectively for a range of mosquito species. I'm eager to check back next week to report on any observations.
https://www.nytimes.com/wirecutter/blog/citronella-candles-mosquito-repellents-dont-work/
Trap 2: Orange Essence
I've read that mosquitoes are generally attracted to sweeter smells, which is why I chose this orange essence as my second bait. I might switch this one out for an old body mist if I don't have much success with the orange, although I'm not sure whether the mosquitoes would be affected by the toxicity of this artificial product. Either way I believe that there could be some oviposition in this trap, I chose this bait as the intermediate bait meaning I think it will attract more than the citronella but less than the cider.
This image is from a couple days after I set the trap, so you can see that many leaves have fallen into my trap. This could affect whether or not female mosquitoes decide to lay their eggs here in a positive way, as the container appears to be darker which makes the habitat more appealing.
Trap 3: Cider
My last bait is the one which I think will attract the highest amount of oviposition because it is the sweetest. This picture is also a couple days after I set it up, so there are snails which have taken to my trap. I am unsure whether this will affect the amount of mosquito oviposition.
These traps are all placed in my backyard, where there is a miniature pond. In Dr. Parker's article it mentions how when given the choice between two potential mosquito habitats, certain species of mosquitos will usually pick the larger habitat. Since the pond is larger than all my traps, it could cause the mosquitoes to lay their eggs there instead of in my traps, which would decrease the number of larvae for my to observe.
EXPERIMENTAL ERRORS
Since I've needed someone else to check my traps while I'm away, the possibility that there was random error caused by relative lack of proficiency in handling this kind of experiment. Some eggs could have been missed if the sides of the traps were not examined properly, and same goes for the larvae.
WEEK 2
Trap 1: Citronella
This trap still did not attract any mosquito oviposition this week, which is evidence to prove that citronella is a mosquito repellent. However, I haven't had much traction with my other traps either, so there could be other environmental factors that are causing this.
This trap did not attract any mosquitos either, although it can be seen in the picture that a lot of leaves fell into the trap. This could indicate that this deterred mosquitos from laying their eggs in this trap. This is slightly contradictory to what was written in the article because in the some of the experiments they conducted to trap mosquito oviposition, they put grass clippings in the trash bins, which attracted the mosquitos. Looking at the picture, it seems like there's been some hot whether because the water level of the trap has decreased significantly. However, there could be some random error in the sampling method because so many leaves have fallen into my trap, which could be hiding some of the mosquito eggs.
Surprisingly, this trap did not have any mosquito eggs or larvae in it, despite being the bait which is known to attract mosquitos because of its sweetness. The water level does seem to have decreased slightly, again an indicator of hot weather.
Same as for the previous week, the number of eggs or larvae could have been miscounted. Additionally, it seems like the water levels in the traps have changed significantly, which could definitely be affecting the mosquito oviposition. In the trap with the orange essence, there is barely any liquid left which is what the females need to lay their eggs.
Week 3 & 4 have no updates worth reporting. No mosquito larvae found in any of my traps.
WEEK 5
For the first time since I started my experiment, I found larvae in my traps!
Trap1: Citronella
To count the number of larvae, I took three samples and counted the number of larvae in each sample.
Sample 1: 11 larvae
Sample 2: 25 larvae
Sample 3: 12 larvae
Then I took the average which was 16 larvae. This didn't seem accurate as there seemed to be closer to 40 larvae total in the trap, so I wasn't sure if this method was wrong but I simply followed the instructions from the Globe Observer App. The mosquito larvae all have long siphons but no teeth on them, and apparently they weren't any species that is being researched by NASA. They weren't Aedes, Anopheles or Culex.
One interesting observation is that there are two identical traps in each area, however only 1 trap had mosquito larvae. The other had none. This suggests that there are other uncontrolled variables affecting the results and causing the females to oviposit in one of the traps over the other, even though the traps were the exact same size, with the same volume of water and surface area.
These traps had no signs of mosquito larvae or eggs. It can be seen that the water level is very low in the trap to the left. It has been hot, but for Copenhagen, the high is 27 degrees celsius. This makes me think that the cats that stroll around the gardens must drink the water from these traps. This means they could be eating the mosquito larvae in these traps.
This trap also did have some mosquito larvae, and it seems to be the same species as in the citronella traps. Again, GLOBE didn't identify it as anopheles, aedes, or culex. I estimated there to be about 130 larvae in my trap. Again, the identical trap right next to it did not have any mosquito larvae in it which meant there must be a difference between the two which is causing mosquitoes to oviposit in one trap over the other.
OVERALL EXPERIMENTAL ERROR
A source of error in my experiment could be that the mosquitoes were not correctly identified due to lack of experience with doing so. To counteract this lack of experience, the guidance from my mentors and peer mentors could be sought out to improve the accuracy of the data that I'm reporting.
CONCLUSION
Overall, the data displayed in this experiment is inconsistent and therefore no conclusion can be drawn on the effect of these different baits on mosquito oviposition. Up until Week 5, no larvae were found in any of the traps. This could also have to do with the season and time of the year, as perhaps the mosquitoes in my area of Copenhagen come out and oviposit in mid July as opposed to mid June. An article by the Metropolitan Mosquito Control District reported that cattail mosquitoes tend to come out in mid-july. This could potentially be the species of the mosquito larvae that I found in my traps, and when comparing my larvae pictures to cattail larvae pictures from this source, they do look quite similar. This would also explain why GLOBE did not identify it as Anopheles, Aedes, or Culex.
The results that were found only supported my hypothesis to a certain extent. The trap which had the most mosquito oviposition was the trap with the cider, but that is based on one week of data, which means that this result is not a reliable indication of the attractive properties of cider for mosquito oviposition. Additionally, it was predicted that the traps with the orange essence would have more mosquito oviposition than the citronella traps, which was not the case based on the last week's results.
About the author: Sophie is a senior at Copenhagen International School, in Copenhagen, Denmark. This blog describes a mosquito trapping experiment conducted as part of the NASA STEM Enhancement in the Earth Sciences (SEES) summer high school research internship. Her virtual internship is part of a collaboration between the Institute for Global Environmental Strategies (IGES) and the NASA Texas Space Grant Consortium (TSGC) to extend the TSGC Summer Enhancement in Earth Science (SEES) internship for US high school (http://www.tsgc.utexas.edu/sees-internship/). Sophie shared her experience this summer in this blog post.
