The Yeah Yeah Yeahs have added ''humour'' to 'Mosquito'.

The indie trio from New York have let their hair down for their fourth studio album after going through a ''dark'' period and aimed to encourage their fans to ''let go'' and have fun while listening to their songs.

Singer Karen O told The Sun newspaper: ''Even though we were in Texas and New Orleans, the stuff we recorded in New York helped the tone of the record.

''It's hard but we have a great sense of humour underlying it. It's what has helped us through the very dark times and allowed us to toe the line comfortably. Finding the humour in our songs and encouraging people to let go and get into it is what 'Mosquito' is all about.''

The artwork for the new record, designed by South Korean-born animator Beomsik Shimbe Shim, sees a florescent pink mosquito with green eyes and while Karen loves it, she admits drummer Brian Chase wasn't initially ''tolerant'' of the design.

Speaking about how the band - also comprised of guitarist Nick Zinner - first reacted to the cover, Karen added: ''Brian hated it for ages. We thought 'Mosquito' was a great title as they've been around since prehistoric times and aren't going anywhere.

''[The artwork is] wild, it's a statement and there's plenty of humour there, like this band. Though Brian really wasn't supportive and tolerant at first.

''I probably had an initial reaction the same as most people when they first see it. Even my dad objected to it. That made the band stand behind it and I do like the confrontation element of the baby versus the mosquito.''

'Mosquito' is out on Monday April 15.