WASHINGTON — They may not be welcome summer guests but they’re certainly expected. And this season there are fewer mosquitoes. Experts are pointing to weather.

Cool overnight temperatures are part of the reason says University of Maryland entomologist Michael Raupp.

“They are temperature dependent. They’re cold blooded and their development depends almost entirely on temperature,” Raupp says.

When mosquitoes don’t develop, they can’t breed.

“When we get these really chilly nights in the low 50s at nighttime and low 80s during the day … it means they complete fewer generations and frankly, it has kept the mosquito numbers down a little bit so far,” Raupp says.

Meanwhile Raupp says there isn’t enough data to support some new apps that claim to detract any winged picnic crashers with high frequency sounds.

“They’re attracted to carbon dioxide, lactic acid, several aromatic alcohols. So the role that sound plays in the host seeking behavior is unknown to me,” he say.

Interestingly, male mosquitoes hone in on the specific sound the pattern of female mosquitoes wings make to find a mate, Raupp says. But male mosquitoes feed on plants, not blood. It’s the females that are biting people.

Follow @WTOP on Twitter and WTOP on Facebook.