If you ignore the fact that mosquitoes are so annoying and dangerous, they really are amazing creatures. Female mosquitoes must find blood in order to reproduce, so mosquitoes come equipped with finely tuned sensors to help them locate the blood they need. With these sensors, mosquitoes can detect carbon dioxide, warmth, certain plant chemicals and sometimes even sweat chemicals. Using these sensors, a mosquito can hone in on a mammal very easily. To learn more, see How Mosquitoes Work.
One easy way to create a mosquito trap would be to take a cow and place it in your yard. The cow would act as the attractant for the mosquitoes, because the cow would give off the chemical signature that mosquitoes crave. A cow is warm, it releases certain plant chemicals (because it eats grass all day) and it produces carbon dioxide with every breath. If you had a vacuum cleaner that could suck up every mosquito that came near your cow, you would have a mosquito trap.
If you used this trap for several weeks, you would start to make a dent in the population of female mosquitoes. After four to six weeks, you could probably create enough of a dent to start to depress the entire mosquito population in your yard. With the number of female mosquitoes down, there would be a lot fewer eggs being laid. That, in turn, would mean fewer mosquitoes, and eventually the population would collapse.
Most neighborhoods do not allow cows, and standing next to the cow to vacuum up the mosquitoes would be labor-intensive, but this trap would work. To make a practical trap, what we need to do is create an artificial cow and an automatic vacuuming system...