Mosquitoes aren’t just a nuisance. Despite their diminutive size, their ability to spread diseases like malaria has made them a persistent threat to human life for as long as we’ve been around. By some estimates, they’ve killed more people than any other single cause in the history of our species.

It’s no surprise, then, that public health officials have a considerable stake in monitoring mosquito activity. To that end, the question underlying this visualization is this: Within New York City, when and where do mosquitoes cause the greatest disturbance?

Overview of the visualization

The general trend in New York City is not much different from what we know about mosquito activity elsewhere: They become more active when temperatures are higher, and they tend to cluster around bodies of water, where they breed. Temperature seems the simplest explanation for why the line graph of total complaints by month has a cyclical shape; complaints spike during the summer months and are almost nonexistent during the winter. This pattern can also be seen in the dot map of complaints by season. 

The extent of mosquitoes’ reliance on water is difficult to parse using a map of New York City not only because so much of the city is near bodies of water, but also because mosquitoes often use the standing water of puddles or ponds, which can be found far from oceans and rivers. Nonetheless, the dot map does indicate that mosquitoes prove especially pesky in particularly wet areas like The Rockaways.

The line graph of complaints by hour of the day shows two spikes: one when the sun is highest in the sky and another around dusk, when mosquitoes are known to be especially active. A look at the bar graph of complaints by day of the week reveals an interesting trend that I can’t easily explain: Complaints seem to spike in the middle of the week. Could it be that New Yorkers tend to take more precautions against mosquitoes on the weekends than on the weekdays are thus less bothered by them? Or perhaps the relaxed mood of the weekend makes people less inclined to file a complaint? It’s hard to say.

Design choices

I thought a line graph appropriate for the change in mosquito complaints from mid-2016 to September 2019 because the shape of the line clearly illustrates the data’s cyclical pattern. I used a line graph for the complaints-by-hour data as well, albeit with a series of steps and not a continuous line; with the staggered steps, I intended to convey that the number of complaints for a given hour took place throughout the whole hour—e.g., from 9:00 to 9:59—not at a given hour on the hour. One limitation I encountered, however, is that I couldn’t figure out how to set the tooltip to display such a range of time when a user hovers over a datapoint. This is something I’ll have to revisit.

The complaints-by-day data seemed best suited by a bar graph; I tried a line graph initially, given that lines are generally better for showing the passage of time. But compared to a simple bar for each day of the week, I think a line made it harder for the viewer to extract the number of complaints, which is the main purpose of the graph. Finally, a dot density map of complaints across all five boroughs seemed the most appropriate way to show geographical trends in the data.

Next steps

Changes to our climate are causing changes in patterns of mosquito activity. As temperatures increase, mosquitoes are able to spread further from the equator and stay active throughout more and more of each year. These trends aren’t apparent in the current data, but they could reveal themselves as more data is collected and as climate changes continues its course.

Another question worth investigating is whether the actions of public health officials have a measurable effect on mosquito complaints. Are there decreases in mosquito complaints in areas in which city services have, for example, removed standing water, sprayed pesticides, and educated people on avoiding mosquitoes?