Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 39 - Molytini (Insecta: Coleoptera: Curculionidae: Molytinae) - Morphological Characters

Craw, RC 1999. Molytini (Insecta: Coleoptera: Curculionidae: Molytinae). Fauna of New Zealand 39, 68 pages.
( ISSN 0111-5383 (print), ; no. 39. ISBN 0-478-09325-X (print), ). Published 4 Feb 1999

Morphological Characters

Morphological terms useful in taxonomy and identification are illustrated for external features (Fig. 11-13), male genitalia (Fig. 62), and female genitalia (Fig. 78).

A character-based phylogenetic species concept (Baum & Donoghue 1995) is adopted in the context of this study. It defines a species as the smallest aggregation of populations diagnosable by a unique combination of character states in comparable individuals.

Head. The globose head is produced into a rostrum that bears the mouthparts, comprising a triangular pair of bi-dentate mandibles with tufted or scattered setae on their outer face, paired maxillae each with a three-segmented maxillary palp, and a rectangular mentum bearing a pair of three-segmented labial palps. There is variation between the species in the relative length, thickness, and shape of the rostrum. It can vary from relatively short and thick with an expanded apex (Fig. 14, 15) to relatively long and thin with the apical portion not much more expanded than the base (Fig. 16, 17). A dorsal median carina occurs in some taxa. The geniculate antennae, inserted laterally on the apical third of the cylindrical rostrum, are eleven segmented with the terminal three segments forming a compact club. The first segment, the scape, contributes almost half the antennal length and is inserted at the anterior end of the scrobe, a deep lateral sulcus extending obliquely from the anterolateral portion of the rostrum to the ventral portion of the eye. Segments 2-8 constitute the funicle, and range in shape from elongate to rounded to transverse. The ratio of the length of the first to the second segment, and the shape of the 7th funicle segment can be diagnostic of some taxa. Eyes are lateral, convex, and transverse.

Pronotum. Diagnostic features of the pronotum include differences in the degree of subapical and basal constriction, macro- and microsculpture, and extent of scaling patterns and punctuation. In Lyperobius the pronotum varies from nearly transverse with broadly rounded sides to elongate with narrowly rounded sides; such distinctions are characteristic of particular species and species-groups. Pronotal sculpture and scale patterning vary from three narrow, longitudinal scale-filled sulci (two marginal, one median) (Fig. 21, 24) through the pale scales being confined to broader, shallower impressions (Fig. 19, 20) to being scattered in no particular pattern (Fig. 22, 23). In the four Hadramphus species the pronotal sides and disc are ornamented with tubercles which in size, shape, and position are specific to species or species-groups. The ventro-anterior lateral margins of the prothorax bear conspicuous ocular lobes which partly conceal the eyes in Hadramphus; these are reduced in Lyperobius.

Elytra. Elytral shape, scale patterns, and modifications of the elytral intervals are all important taxonomic char-acters. The degree of prominence of elytral humeri, and the development and shape of discal and declivity tubercles, differ greatly between the Hadramphus species (Fig. 1-4). The extent and development of raised costae on the even and uneven intervals offer a number of useful distin-guishing features in Lyperobius (Fig. 5-10, 27, 28). The shape of the pale scales can vary considerably on a single individual, but scale shape is usually relatively constant on the elytral disc, and can serve as a useful diagnostic character.

Legs. The legs can vary from elongate and slender with the femora barely claviform and the tibiae straight (e.g., H. spinipennis) to short and thick with the femora gradually claviform (e.g., L. cupiendus) and the tibiae short and sinuate (e.g., L. fallax). The extent and position of scaling on the upper inner face of the coxae is an important character diagnostic of the L. coxalis species-group (Fig. 32-34). Size and shape of the second and third tarsal segments, and the degree of development of the tarsal sole hairs, offer useful diagnostic characters for distinguishing both sympatric congeners and vicarious sister taxa (Fig. 36, 37).

Sexual dimorphism. Apart from minor differences in shape of the rostrum between the sexes, dimorphism is most readily observed in the fifth ventrite. The male ventrites are smaller and much more transverse (Fig. 38, 40, 42) than the female ventrites, which are larger, longer, and more rounded on their margins (Fig. 39, 41, 43).

Genitalia. The male median lobe is stout and robust, as is characteristic of molytine weevils. Size and shape of the median lobe and the development of the aedeagal apo-demes relative to the median lobe can be characteristic of a particular species. The shape of the endophallic basal sclerite, and the presence or absence of sclerites in the endophallus apex, can be useful diagnostic characters (Fig. 48-69). In the female genitalia size and shape of the 8th sternite are useful features for distinguishing species (Fig. 70-76). Degree of development of the hemisternal pouches, size and shape of the hemisternites and styli, and the nature of their setation can vary greatly between species (Fig. 77-83).

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