.butterfly {
  position: absolute;
  height: 40px;
  width: 30px;
  z-index: -5;
}

#b1 {
  background-image: url('../images/b1.png');
}

#b2 {
  background-image: url('../images/b2.png');
}

#b3 {
  background-image: url('../images/b3.png');
}

#b4 {
  background-image: url('../images/b4.png');
}

#b5 {
  background-image: url('../images/b5.png');
}

#b6 {
  background-image: url('../images/b6.png');
}

#b7 {
  background-image: url('../images/b7.png');
}

#b8 {
  background-image: url('../images/b8.png');
}