I divide the genus Eretmocerus into 8 species groups based on the number of pairs of setae on the midlobe of the mesoscutum (MS) and the length/width ratio of the antennal club (L/W). These groups have no taxonomic status. They are are useful as an identification tool to group species together that have these two characters in common, but do not necessarily signify that the species belonging to a group are phylogenetically more related to each other than to members of another group.
 

Table 1. Eretmocerus species groups
 

Species group	MS  setae	Club L/W	Species
bisetae	1	<5x	bisetae
diversiciliatus	1	>5x	diversiciliatus
paulistis	2	<5x	desantisi, debachi, furuhashii, jimenezi, nairobii, neobemisiae, nikolskajae, paulistus, rajasthanicus, roseni, sculpturatus, siphonini
mundus	2	>5x	clauseni, emiratus, hayati, indicus, longicornis, melanoscutus, mundus, mundus parthenogenetic form, rosei, zippanguiphagus
longipes	3	<5x	aleurothrixus, breviclavus, flavus, joeballi, lativentris, longipes, longiterebrus, portoricensis
californicus	3	>5x	adustiscutum, aleyrodiphaga, ampliatus, australis?, californicus, comperei, corni, delhiensis, dialeurolongae, dozieri, eremicus, exilis, gracilis, gunturiensis, haldemani, hydrabadensis, illinoisensis?, longiscapus, nativus?, orientalis, pallidus, queenslandensis, serius, staufferi, tejanus, trialeurodis, warrae
cadabae	>3	<5x	cadabae
silvestrii	>3	>5x	aleurolobi, silvestrii
unplaced	?	?	aleyrodesii