Length: 6-8 mm
Paskewitz and McPherson (1983) studied the life history of one species of Arhyssus in the field and in the laboratory. They found Arhyssus lateralis feeding and reproducing on Curly Dock, Sheep Sorrel, Pennsylvania Smartweed, and Swamp Smartweed. The key dates such as oviposition varied depending on which host plant was being used.
The authors concluded that Arhyssus lateralis was bivoltine in their Illinois study area, and that the species overwintered as adults.
In the lab, Paskewitz and McPherson raised the species on Sheep Sorrel, which was both their food and a location for egg-laying. Eggs took an average of 9 days to hatch. From hatching to the final molt to adult took 29 days.
The authors described the various instars; the fifth instar nymph measured 5 mm long and the ratio of length of antennal segments was about 12:19:18:25.
American Insects site