Diagnostic morphological characteristics of Pentalonia nigronervosa and Pentalonia caladii

Pentalonia nigronervosa was collected on Zingiberaeae and Muscaeae, and Pentalonia caladii was collected on Heliconiaceae and Araceae on Guam. Measurements of the ultimate rostral segment, body length, length of the siphunculi and length and width of the cauda were made for each species. P. nigronervosa had a longer ultimate rostral segment on average than P. caladii, and also had longer siphunculi and caudae. These characters may prove useful in differentiating between these two aphid species in the field.