MESOPTILIINAE Lacordaire, 1863
Our single genus includes very distinctive weevils associated with a range of trees and shrubs. Most species are restricted to certain host plants.
This diverse subfamily includes about 250 species in 15 genera and, with the exception of tropical Africa, is cosmopolitan. Three tribes are represented in The Palaearctic region; Carciliini Pierce, 1916 includes five species of Carcilia Roelofs, 1875 from the Far East, Mesoptiliini Lacordaire, 1863 with the single species Eumagdalis grilati Bedel, 1885 from Algeria, and Magdalidini Pascoe, 1870 by the single genus Magdalis Germar, 1817. Magdalis includes about 100 species in 9 subgenera and occurs throughout most of the world while the greatest diversity is in the Palaearctic region; 25 species are known from the USA and 53 species in 8 subgenera are Palaearctic of which 19 occur in Europe and 9 species of 5 subgenera extend to the UK. Some authors include the group in the subfamily Pissodinae Gistel, 1848, a group now included as a tribe of the large subfamily Molytinae Schoenherr, 1823. Species of Magdalis are distinguished from other UK weevils by the base of the elytra which is deeply excised medially, the scutellum lying at the apex of this incision and behind the basal elytral margin. All are elongate, dorsally rather flat and either near parallel-sided or with the elytra gradually broadened towards the apex, entirely black to dark brown in colour, sometimes with a blue or green reflection and sometimes with parts of various appendages paler. They lack scales and have, at most, very fine hairs to the dorsal surface. The head is proportionally small with small, weakly convex eyes that follow the outline, the vertex is variously punctured and the interocular distance is about as wide as the rostrum which is usually long, curved and near parallel-sided. Antennae rather long, with a long and narrow scape and very variable club. The pronotum is quadrate to elongate, variously punctured and simply convex, without structure or lateral borders although in some there are lateral tubercles or the anterior angle is produced into an acute tooth. The prosternum is not deeply channelled for the reception of the rostrum and the mesepimera are not visible from above. In most the pronotum and elytra are continuous in outline or nearly so; in some the elytra have broad shoulders and are clearly broader than the pronotal base. Elytra continuously or separately rounded at the apex and often exposing part of the pygidium, with distinct punctured striae, the punctures often elongate, and narrow, usually finely punctured interstices. Legs long and slender, femora with or without an internal tooth, femora smooth externally; the outer margin of the pro-tibiae are curved and extended at the apex into a sharp inward-facing tooth, tarsi 5-segmented with the third strongly lobed and often concealing the fourth, claws free.
With a little experience species of Magdalis are readily recognized in the field but they should be examined critically for certain identification, especially as individual species vary widely in size. Adults may be samples by beating or sweeping the host plants; species of Magdalis s.str. are associated with conifers while the rest occur on various broadleaf trees and shrubs. They have a short season during late spring and early summer, eggs are laid in or below bark and larvae mine beneath the bark or in the xylem, pupation occurs in the tunnels and adults remain in the wood, often in numbers in tightly packed borings. Several species are widespread and common and should soon be found by beating etc.
The British species can be identified using the following key:
Front femora with a distinct ventral tooth.
Front femora smooth or with only a very weak and inconspicuous tooth
Pronotum sinuate laterally and narrowed anteriorly; the basal margin much wider than the apical, anterior angle obtuse or rounded
Pronotum weakly curved laterally, the apical and basal margins subequal in width, anterior angles produced into a tooth
Elytra black, without a coloured reflection. Elytral stria with large punctures, as wide as the interstices, base of each elytron strongly rounded and obviously overlapping the pronotal base. 4.5-8.2mm.
Elytra with a distinct metallic blue or purple lustre. Elytral striae less strongly punctured, narrower than the interstices, base of each elytron weakly curved and not, or barely, overlapping the pronotal base.
Eyes flat or only weakly convex, more-or-less continuous with the outline of the head. Pronotum transverse. Front femora smoothly narrowed to the base. 3.0-4.7mm.
Eyes distinctly convex and protruding from the outline of the head. Pronotum elongate to quadrate. Front femora constricted near the base. 3.1-6.1mm.
Pronotum with a strong and sharp tubercle behind the anterior angle, lateral margin only weakly rounded and with a sub-basal constriction. Elytral striae less strongly and more shallowly punctured, the interstices flat or weakly convex, obviously strigulate and dull. 2.8-5.1mm.
Pronotum with a much smaller tubercle behind the anterior angles, hardly larger than the surrounding asperites, lateral margin strongly rounded. Elytral striae more strongly and deeply punctured, the interstices obviously convex, less strongly strigulate and rather shiny. 3.1-6.2mm.
Upperside brown, sometimes darkly so, underside contrasting black. Appendages brown.
Body unicoloured, appendages dark.
Pronotum with a sharp tooth towards the lateral margin in the posterior half. Rostrum shorter than the head and continued from the frons in a straight line, in lateral view not angled above the eyes. Antennae reddish with the two basal segments paler; club shorter than the scape or the funiculus. 2.4-3.8mm.
Pronotum smooth, without a lateral tooth. Rostrum at least as long as the head, in lateral view forming a distinct angle with the frons. Antennae otherwise, and modified in the male.
Antennae dark brown to black, club in male longer than the funiculus or scape, in female about as long as the scape. Femora with a very small ventral tooth, in rare cases missing. Pronotum more transverse and more rounded laterally. 2.4-4.2mm.
Antennae pale, at least towards the base, often entirely red; club in male almost as long as the scape and funiculus combined, in female shorter than either. Femora smooth ventrally. Pronotum less transverse and less rounded laterally. 3.1-4.1mm.