Aphodius erraticus (Linnaeus, 1758)
Common throughout England and Wales but less so in the north and south east in various types of dung; Jessop quotes sheep, horse and pig, in our experience cattle as well. A late spring and summer species also overwintering as an adult. Prefers exposed habitats. Widespread and common throughout the Watford area in cattle and horse dung in all local habitats. Unlike most other local Aphodius spp. we have never found this species in numbers, where there is an abundance of dung at least some samples usually contain only a pair of specimens. They first appear in May and then remain common until mid August, depending on season.

Distinctive; 6-9mm, scutellum long (≥ 20% sutural length), pronotum evenly punctate, without larger punctures, and elytral interstices finely punctured. Head and pronotum dark, elytra ochreous to brown with sutural interval dark.
A. erraticus (L.) ab. fumigatus has disc of elytra dark and margins lighter see Donisthorpe, H., 1934 Ent. Mon. Mag. Vol 70 p. 230.

Description from 6 Watford specimens at X20