Morphology of three Brazilian species of Semiotus ( Coleoptera , Elateridae , Semiotinae )

The morphology of Semiotus distinctus (Herbst, 1806), S. intermedius (Herbst, 1806) and S. ligneus (Linnaeus, 1767), including mouthparts and male and female genitalia, is described and illustrated. A comparative analysis of the characters related to the external morphology, mouthparts and male and female genitalia is also included.

The genus Semiotus includes large sized and colorful beetles (14-48 mm), with very bright integument.The coloration is usually yellow with longitudinal stripes black, orange or reddish.Since now, it has been characterized especially by antennae 11segmented and serrate; mandibles toothed; tarsal segments 1-2 lamellate beneath; each elytron with one or two distal spines; last ventrite entire with rounded apex in both sexes and bearing, in female, two fossae clothed with short setae.The mouthparts and genitalia male and female had not been studied.
Herein, the morphology of three species, very common in Brazil, are described and illustrated.
For illustrations, the mouthparts, genitalia and genital segments of male and female were temporarily mounted in glycerin on a slide and drawn with the aid of a camera lucida attached to a stereomicroscope.
Redescription.Length: 15-44 mm.Bright, coloration from yellowish-brown to ferrugineous with longitudinal stripes on pronotum and elytra brownish or yellow (fig.3).Antennae dark-brown or brownish with two first articles brownish or yellow.Pronotum yellow with three wide brownish longitudinal elliptical stripe not reaching margins.Scutellum marginated by brownish band.Elytra brownish with apices yellow; narrow yellow band on 2nd interstice and at lateral margins.Hypomera and sides of ventrites 1-4 with longitudinal brownish patches.Pubescence thin and sparse, yellowish or brownish, longer ventrally.Frons narrow, rectangular, strongly grooved at middle, forming a triangular concavity; fore angles raised and rounded; punctation sparser and thinner than pronotum.Antennae (fig.46) surpassing hind angles of pronotum in one article in male; in females almost reaching them; 11-segmented and serrate from 3rd article, stronger in males.Labrum (fig.47) transverse, semicircular, marginate by irregular fringe of long setae.Epipharynx membranous, densely clothed with thin and clear setae and sensorial pores near middle, some in group.Mandibles (figs.50, 51) symmetrical, narrow, with apex curved and a subapical tooth; dorsally raised, with a median carina and setae of varied sizes near lateral margin; penicillum formed by fringe of short and thin setae.Maxillae (fig.49): cardo subtriangular, projected distally, with moderately long basal setae near middle; basistipes bearing long setae near middle and mediostipes punctuate near middle; galea and lacinia brush-like, densely clothed with short setae.Palpifer sclerotized and setous near base; antenna;28,labrum;29,maxilla;30,31,mandible (dorsal,ventral); 32, labium; 33, apex of prosternal spine and mesosternum (lateral).Male: 34, tergites 9-10; 35, sternite 9; 36, tergite 8; 37, sternite 8. Bars = 1 mm.maxillary palpi 4-segmented and setous; basal segment transverse and distal elongate with apex strongly securiform.Labium (fig.52): mentum membranous on anterior half, bearing setae of varied sizes on basal sclerotized half; ligula marginate by fringe of short setae with a group of long setae near middle.Palpiger separate, bearing 4 setae of varied sizes; labial palpi 3-segmented and setous; distal segment strongly securiform.Hypopharynx totally clothed with thin, yellowish and moderately long setae.Pronotum rectangular, slightly widened basad; convex and slightly grooved near lateral margins; anterior margin sinuous, slightly prominent and raised near middle; fore angles prominent, rounded and flat; hind angles very prominent backwards, slightly raised Remarks.Comparing the studied species it was observed that S. distinctus is similar to S. intermedius in coloration, but the latter presents fore angles of frons toothed and two longitudinal stripes on pronotum.In both species the last ventrite of female presents two elliptical fossae clothed with short setae and palpiger bearing 5 setae.S. distinctus differs from S. ligneus in coloration, but both species present the following characters: antennae of male longer than hind angles of pronotum, labrum semicircular, last article of labial and maxillar palpi strongly securiform, prosternal spine bilobed at apex and parameres of aedeagus with subapical lateral unciform tooth.S. intermedius is similar to S. ligneus specially by: anterior margin of sternite 8 of female widely notched and spiculum gastrale 4.7 times sternite length.CANDÈZE (1857) included S. distinctus and S. intermedius in different groups, based specially on the presence or absence of teeth at anterior margin of frons.S. distinctus and S. ligneus were included in the same group.
Semiotus distinctus is characterized specially by anterior margin of sternite 8 of female strongly notched and spiculum gastrale 4 times the sternite length; S. intermedius, frons with two anterior teeth, labrum subrectangular, basal piece of parameres long and bursa copulatrix with anchora-like sclerotized piece, and S. ligneus, palpiger bearing 4 setae and last ventrite of female with two rounded fossae clothed with short setae.
Based on the studied material, it was verified that S. ligneus presents a wider geographical distribution, being recorded from Mexico, Panama, Colombia, French Guiana, Brazil, Peru, Bolivia and Argentina, while S. distinctus is recorded from Brazil, Argentina and Paraguay and S. intermedius is restricted to Brazil.