NANOPHYINAE Gistel, 1848

No Common Name

Nanophyes marmoratus can be found anywhere the foodplant, Purple loosestrife grows, whereas Dieckmanniellus gracilis is a very local species, found on Water purslane.

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POLYPHAGA Emery, 1886

CURCULIONOIDEA Latreille, 1802

BRENTIDAE Billberg, 1820

Dieckmanniellus Alonso-Zarazaga, 1989

Nanophyes Schönherr, 1838

0.7-2.1mm

Around the World

This relatively small group of weevils contains more than 300 species included in more than 30 genera although there have been many recent changes, albeit not universally accepted, and so the number of genera is likely to increase; the large genus Nanophyes Schoenherr, 1838 formerly included about 150 species but is now split into several others e.g. Nanodes Schoenherr, 1825, Diekmanniellus Alonso-Zarazaga, 1989, Microon Alonso-Zarazaga, 1989 and Nanomimus Alonso-Zarazaga, 1989. The group is sometimes classed as distinct family, but is here included as a subfamily of the Brentidae Billberg, 1820 including two tribes: Corimaliini Alonso-Zarazaga, 1989 includes four genera and about 25 species, and the remainder are included in the Nanophyini Gistel, 1848. Members of the Corimaliini are distributed from central Asia to the Near East and Mediterranean regions and several occur in Africa (Namibia), all four genera are represented in the south of Europe. Members of the Nanophyini occur worldwide with the exception of South America; they are most diverse in the Far East and Southern Asia and least so in the Nearctic region; five genera have been recorded from the United States, three of which are monotypic, and include the introduced Palaearctic Nanophyes marmoratus (Goeze, 1777) and a member of Microon, M. canadense (W.J. Brown, 1944), a genus which is also Palaearctic. The Palaearctic fauna includes about 80 species of which about 40, included in 14 genera, have been recorded from Europe and of these 25 occur in France and 7 in Scandinavia, the U.K. fauna includes only two species and is by comparison very poor. The subfamily is similarly only poorly represented in Australia; the single endemic genus Austronanodes Zimmerman, 1993 (formerly included in Nanophyes) includes five species.

Ecology

The species are mostly monophagous or oligophagous on a wide range of plant families e.g. Ericaceae, Crassulaceae, Cupressaceae, Lytraceae, Myrtaceae and Oliniaceae. In some cases the members of a genus share the same host  range e.g. species of  the genus Corimalia Gozis, 1885, with

about 20 Palaearctic species, feed and develop on Tamaricaceae while Austronanodes utilize Gentianaceae and Haloragaceae. Adults and larvae generally share the same host, and some plants host several species e.g. Nanophyes marmoratus (Goeze, 1777), N. Globules (Germar, 1821) and Nanomimus circumscriptus (Aubé, 1864) develop on Lythrum salicaria while Microon sahlbergi (Sahlberg, 1835) and Dieckmanniellus gracilis (Redtenbacher, 1849) develop on Lythrum portula. In such cases the various species generally utilize different plant tissues. Polyphagy is rare but is seen in the widely distributed Diekmanniellus nitidulus (Gyllenhal, 1838). Adults tend to feed on young tender foliage and petals while larvae develop in flower buds, stems and leaves, sometimes forming galls. Pupal cells are often formed in unopened flower buds which usually fall to the ground once the larvae begin feeding; pupae of Corimalia species can ‘jump’ within the cell and cause the bud to move or bounce across the ground, presumably allowing them to avoid adverse environmental conditions. In temperate zones there is a single generation each year with the adults over-wintering. In tropical areas there may be several generations each year.

Description

All are small weevils, 0.70-5.7mm although most are <2.5mm. They are elongate-oval and continuous in outline although some are rather parallel sided e.g. the Nearctic Pseudotychius watsoni Blatchley, and in some the elytra are straight and tapering towards a distinct angle before an oblique apical margin. In most the shoulders are broad and the dorsal surface is distinctly scaled or pubescent, they are rather drab coloured; black to orange with various pale markings or bands of pubescence although some are striking e.g. the Nearctic (Texas) Zeugonyx sabinae Notman, 1922 which is bicoloured, black with bright red elytra. These atypical forms tend to resemble the Curculionid subfamily Ceutorhynchinae. The head is relatively small with large convex eyes that occupy most of the lateral margin, and narrow vertex and frons, in some cases the eyes are almost touching. The rostrum is long and weakly curved, sometimes almost straight, and usually has a longitudinal keel or furrows. The antennae are geniculate and inserted laterally about the middle of the rostrum; funiculus 4-6 segmented, both U.K. species have 9-segmented antennae with a 5-segmented funiculus, scape as long as or longer than the remainder of the antenna and usually thickened near the apex, the second segment slightly broader or widened apically to form a pedicel. The club is three segmented and compact in Corimaliinae or loose in Nanophyinae. Maxillary palpi 3-segmented, labial palpi 2-segmented. Pronotum broadest at the base and narrowed anteriorly; the anterior margin often about half the width of the posterior margin, and without lateral borders or basal fovea. The base of the pronotum and the elytra are finely crenulate. The elytra completely cover the abdomen, are convex and have well impressed striae complete to the apex; interstices convex, usually broad compared with the striae, and generally have some longer sensory setae among the finer pubescence. The colour and pattern vary widely in many species; generally many have contrasting obliquely transverse bands of colour or pubescence. The pro-coxal cavities are closed posteriorly and the meso-coxae are widely separated by the meso- and metacoxal processes. Abdomen with five visible sternites although some basal or apical segments may be fused and the sutures obsolete, the basal sutures are recurved laterally.  The legs are long and slender with the coxae projecting at least to some extent, trocanters long and obvious in lateral view and separating the coxae and femora. Femora clavate and variously toothed; the profemora may bear a strong internal tooth. The tibiae are long and slender or only weakly broadened distally and the shape may vary between the sexes, variously toothed apically or subapically. Tarsi 5,5,5, the fourth very small and often hidden within the bilobed third segment. Claws smooth and connate in Nanophyinae or free in Corimaliinae; paired and of equal length in most species, or single e.g. in the south European and African Nanodiscus transversus Kiesenwetter, 1850 (formerly Nanophyes).

The small size and compact oval form of these weevils is suggestive of Apioninae but the form of the antennae is distinctive. Both of these groups are distinguished from other curculionid families by the possession of long trocanters which can readily be appreciated in lateral view in carded specimens. Among the U.K. fauna our species are obvious by their general appearance. On a wider scale the families are easily distinguished:

  • NANOPHYINAE:                                                                                                                                                                              Antennae geniculate; funiculus 4-6 segmented, 5-segmented in Palaearctic species, scape >half the length of the remainder of the antenna. Pronotum campanulate; the base as broad as the base of the elytra, and strongly narrowed to the anterior margin. Body continuous in outline. Basal abdominal sutures recurved laterally.

  • APIONINAE:                                                                                                                                                                                    Antennae orthocerous; funiculus 7-segmented, scape at most less than half the length of the remainder of the antenna. Pronotum parallel-sided, rounded or weakly narrowed anteriorly, the base narrower than the elytral base so that the outline is discontinuous. Basal abdominal sutures straight.

UK Species

The species of Nanophyinae can be very difficult to identify and even among the European fauna some will need to be dissected and identification will rely on the males, but with only two genera represented in the U.K. this is straightforward. Colour tends to be very variable in many species, including those in the U.K. and, apart from typical specimens, is not usually helpful.

0.7-2.0mm. Femora with two small and sharp teeth on the inner margin, the inner tooth larger; these are most obvious on the front legs. Rostrum longer; in the female as long as the head and pronotum combined, in the male a little shorter. Male hind tibiae curved and all tibiae with a distinct apical tooth. In the female all tibiae lack an apical tooth and are straight.

1.0-2.1mm. Femora smooth although in some specimens there may be a single small tooth on the pro-femur. Rostrum longer in the male but shorter than the head and pronotum combined in both sexes. Male hind tibia straight, and all tibiae have a very fine apical tooth.

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