Photo of melon aphids
Melon aphids are often found distributed along the midrib on the underside of a host plant. The aphids range from 1.0 to 1.8 mm long (ca. 1/16 inch) and from pale yellow to green to dark green (almost black) with multiple colored individuals in a single colony. There can be winged as well as wingless forms – latter enable the aphid to seek other plant hosts.

Photo Source: Michael Bush, Washington State University Extension, Yakima, WA