Abstract
The aphid genus Coloradoa Wilson, is reported for the first time from the Kingdom of Saudi Arabia. The species Coloradoa rufomaculata (Wilson, 1908) was found feeding on Ambrosia maritima L. (Asteraceae) representing a new host plant. This species is widely dispersed in Europe, North America, eastern Asia, Japan, Africa, and the Middle East. A brief description of the species is provided with biometric data. These specimens were compared with descriptions in literature. Morphological variability in commonly used taxonomic characters has been discussed. Rostrum shape and antennae length have similarity with available literature and most important variable characters are siphunculi color, polygonal reticulation on 8th abdominal tergite and rostrum length.