SEES 2022: Testing the size of trap openings on Mosquito Oviposition

Purpose:

The purpose of this experiment is to determine whether the size of trap openings affects mosquitos' preferences to oviposit. Basically, I wanted to study if mosquitos are attracted to a source more if it is more accessible with a wider opening, or if this didn't play a role in their egg-laying preferences. 

Background Information:

According to preliminary research, mosquitos are able to locate and pass through small gaps and holes such as holes in mosquito nets. They do this by first sensing the source (usually they detect human blood and carbon dioxide) and then after locating the source or attractant, they will fly towards it. According to studies conducted by Andrew Dickerson, Ph.D., and other researchers at the University of Central Florida, mosquitos are able to pass through small openings after sensing attractants. It is not a flawless pass-through, and part of it is up to chance, but the study determined that mosquitos in fact are able to find and pass through small openings, specifically bed netting and net screens.

This relates to my study because it hints that mosquitos may still be attracted to the trap with the smallest opening size. Therefore, the size of the opening may not matter as long as there is a strong enough attractant in each of the traps.

Source: https://entomologytoday.org/2018/12/05/hole-story-how-mosquitoes-seek-gaps-nets-screens/

Procedure:

For my traps, I constructed plastic bottle traps out of empty 2L soda bottles. First, I cut the tops off of the clean bottles at the same height to give each bottle an opening that was the same diameter as the bottle itself.

Then, I had to make the openings of the bottles. I decided to create one trap with a large opening, one with a medium opening, and one with a small opening. For the large opening, I left the bottle the way it was with the cut-off opening. For the medium opening, I took the top part of the bottle that I cut off and made the top hole a little wider. Then I placed it upside down on the top of the bottle to give the bottle a medium-sized opening. For the small opening, I did the same thing as the medium bottle but made the hole smaller to create a smaller opening.

After constructing the traps, I filled all 3 of them up with the same amount of water. Then, I placed grass, twigs, and one small stick in each trap along with a dollop of honey that served as the bait.

After the traps were fully prepared, I placed them all in a 5-meter radius in a shady wooded location. To ensure they were all stable, I placed a large rock in each of them which helped to weigh them down.

Each week, to check the traps, I brought them out of their shaded locations and took the lids off. After observing the traps, a small cup was used to scoop water out that potentially had larvae. This water was dropped onto a small white-colored lid and a magnifier that was clipped to a phone was used to observe the sample and take pictures. After the observations were complete, the traps were not dumped, in case they contained mosquito eggs, but they were filled with water to ensure they all had a constant water height, and then were placed back in the shaded location.

Results:

After 6 weeks of this experiment (5 observations), there were no mosquito larvae found in any of the 3 traps. In the trap with the small opening, larvae were observed, but they were not mosquito larvae. Additionally, many various dead bugs were found in all 3 traps. It is interesting to note that the trap with the small opening had the highest volume of larvae and bugs. Additionally, dead slugs were also found in the trap with a large opening and the trap with a medium opening. Other observations included a formation that appeared to be an egg raft of mosquito eggs, but upon closer examination, it ended up being a cluster of spider eggs.

• Weekly Observations for Trap 1:
• Weekly Observations for Trap 2:
• Weekly Observations for Trap 3:

Challenges:

• After the first 2 weeks, some of the traps were found knocked over. To fix this, I made sure to apply pressure when placing them down so that they would get indented in the dirt.
• After the first week, the trap with the medium-sized opening had lost its lid, essentially giving it a large-sized opening. To counter this, I re-inserted the lid and then secured the lids on all the traps with duct tape.
• At some points during the experiment, the traps lost water, either due to getting knocked over or due to evaporation. To counter this, whenever a trap was found with less water, I filled it up to the pre-determined line. Similarly, some traps were found with more water, due to storms or heavy rains. However, whenever this happened, I did not even out the water level by dumping water out because I did not want to lose any mosquito eggs or larvae that were possibly also in the water. Instead, I filled the other traps up with more water so that the traps all shared a constant water level.
• The location that the traps are in is around a residential area. The properties in this area are regularly treated with a mosquito repellent spray. This challenge could be a potential reason why no mosquito larvae were detected.

Conclusion:

Because no mosquito larvae were found, no determination can be made about the relationship between the size of trap openings and mosquito oviposition.

However, these minimal results suggest that there may be a relationship between the size of trap openings and bugs in general. The most bugs and unidentified larvae were found in the trap with the small opening, and the least were found in the trap with the large opening. These observations suggest a correlation between these two components, but further research and studies will be required to determine causation and a conclusion.

Thank you to the NASA SEES project mentors and organizers for giving me the opportunity to participate in this research internship and conduct this experiment. 

About the author: Aarnav is a senior at Mahwah High School, Mahwah, NJ. 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. His 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/). ​​​​​​​