Within the Hemiptera, the Sternorrhyncha form the largest and most complex group. Within the Sternorrhyncha, the same applies for the Aphidomorpha, the aphids and relatives. Aphidomorpha have an exceedingly long proboscis (that may be retracted within the when not in use).
In the Phylloxeridae, a small aphid family, no host alternation takes place; host plants are deciduous trees. In the parthenogenetic phase no living young are born, like in the true aphids, but unfertilised eggs. Some species may induce strong galling.
Blackman & Eastop (2014), Börner & Heinze (1957a), Richards & Davies (1977a).