Visual acuity
Visual acuity, the clarity of vision, can be determined in arthropods by determining number of lenses in their compound eyes and the interommatidial angle (shortened as IOA and referring to the angle between the optical axes of the adjacent lenses). The IOA is especially important as it can be used to distinguish different ecological roles in arthropods, being low in modern active arthropod predators. "Slimonia" was very similar to the basal pterygotid "Erettopterus" in terms of visual acuity, with the number of lenses being comparable to those of "Pterygotus" and "Jaekelopterus" and possessing an IOA between 2 and 3 (which is higher than the IOA of "Pterygotus" and "Jaekelopterus", suggesting that the visual acuity of "Slimonia" was good, but not as good as in the derived pterygotids).