Cionus tuberculosus (Scopoli, 1763)
A locally common species throughout southern England north to Cambridgeshire, Leicester (older record) and Gloucester and west to north Somerset and west Dorset (NBN). There are Welsh records from Monmouth and Glamorgan and Scottish records from Kintyre north to west Perth (Morris). Included on our Watford list from several adults swept from mixed herbage growing beside disused watercress beds below cassiobury park during May and June 2008. Both adults and larvae are ectophagous on various species of Scrophulariaceae, particularly Scrophularia auriculata (=S.aquatica) (Water Figwort), a common species of pand margins and ditches, and S.nodosa (Figwort) a common species of woods and hedge banks. Records from Verbascum spp. are unconfirmed.

An account of the biology is given by Reed (1977). Oviposition occurs mostly in the leaf mid ribs and petioles; the female eats a small and deep hole in the rib into which a few eggs are laid, after this the hole is sealed with a secretion from the abdomen. Under observation a female laid nearly 300 eggs in 61 leaves over a 26 day period commencing early in July (second generation?). After hatching the larvae eat through the cavity wall and feed on the upper surface of the leaf, producing small round holes. As they grow they feed through all cell layers so producing large open holes around the veins and the main stems. Mature larvae spin a silken cocoon on the underside of the leaves or beneath the flower buds, sometimes in small groups. Adults emerge by cutting a small flap in the base of the cocoon, after emerging they begin to feed on the undersuface of the leaves where they produce large holes, and also on the stems and seed heads. Adults almost certainly overwinter, probably in the soil around the base of the plant, and there is either one or two generations each year.

The general form of Cionus is unique among the British fauna and cannot be mistaken for any other genus.

3.4-4.2mm (Morris). Entirely black but for reddish brown tarsi. Eyes convex and relatively large, occupying almost the entire head, temples curved and broadened to base. Vertex behind eyes densely and quite strongly punctured. Distance between eyes narrow, about 2/5 width of base of rostrum. Rostrum long and curved, punctured throughout and flattened beyond antennal insertions. Antennal scape gradually widened in apical third, funiculus 5-segmented, club 3-segmented and pubescent. Pronotum broadest at base, sides curved to straight fron margin. Without borders, cuticle shiny and finely punctured. Sides with dense pale scaling, disc without, or virtually without, scales. Elytra slightly elongate; 29:34 (and deep, height 24),much broader than base of pronotum. Appearance predominantly dark with a chequered pattern produced by areas of dense black scales to interstices 1,3,5,7 and 9 (other interstices have much smaller patches) and a sparse covering of small pale scales. Humeral projection between the bases of interstices 7 and 9 well developed and prominent. Posterior margin of basal round black mark (behind scutellum) with a patch of white scales. Basal, and sometimes apical, margin of posterior dark mark with white scales. Legs sparsely clothed with elongate pale scales. All femora strongly toothed, front femora about as strongly as hind femora. Apex of front tibiae rounded, without projections. Third tarsal segment strongly bilobed, fourth tiny, fifth elongate and curved. Claws united at base, in the male the protarsal claws are unequal in length.

Description from 2 Watford specimens

Read, R.W.J 1977. Notes on the biology of Cionus scrophularia, together with preliminary observations on C.tuberculosus and C.alauda. Ent. Gazette 28:183-202