Hadromychus, Bousquet & Leschen, 2002

Bousquet, Yves & Leschen, Richard A. B., 2002, Description Of A New Genus And Species Of Endomychidae (Coleoptera: Cucujoidea) From Northeastern North America, The Coleopterists Bulletin 56 (2), pp. 291-298 : 293-296

Hadromychus , new genus

Type Species. Hadromychus chandleri new species.

Etymology. A combination of the Greek word hadros, meaning well­developed, in reference to the enlarged ninth antennomere of the male, and ­mychus, part of the family name Endomychidae .

Diagnosis. Antennomere 9 expanded in male and lacking setigerous patch; pronotum lacking longitudinal sulci, with basal groove and two pair of foveae; prosternal process very narrow and cariniform; mesosternum with a pair of foveae just in front of coxae; four subcoxal foveae present on first visible abdominal ventrite; elytral punctation arranged into rows; hindwing with anal lobe.

Description. Body elongate, convex, covered with decumbent hairs; cuticle of ventral foveae annulate. Head prognathous; vertex without stridulatory file. Labrum more or less rounded. Tormae with mesal arms symmetrical and recurved anteriorly. Mandible lacking strongly developed secondary teeth on incisor edge, with single apical tooth on right one, with apical and subapical teeth on left one; pore field on surfaces reduced; outer edge not denticulate. Lacinia and galea narrow; lacinia brushy, width about ½ that of galea. Labial palps not aciculate, terminal palpomere slighty narrower than basal one. Mentum more or less quadrate with anterior edge straight, membrane slightly wider than sclerotized part and slightly invaginated. Eyes well­developed, coarsely faceted, interfacetal setae present. Antenna 11­segmented with 3­segmented club; antennomere 9 of male swollen, much larger than antennomeres 10 or 11 and lacking setiferous sex patch; antennomeres 4 and 5 subequal in length; antennal insertions hidden in dorsal view by slightly raised areas of frons. Tentorium without median spine; corporotentorium curved. Pronotum explanate laterally, with sublateral carina on each side prolonged inside anterior angle but not along anterior margin; base with transverse groove ending on each side in pair of pits, basal bead and sublateral sulci absent; anterior angles slightly produced; anterior edge without stridulatory organs. Prosternum in front short, shorter than width of procoxa, with setose fovea in front of each coxa; prosternal process very narrow and cariniform, not protuberant, not prolonged to posterior end of coxa; procoxal cavities externally open; procoxae contiguous; trochantinal notch absent. Mesosternum cariniform medially (unicarinate); procoxal rest with fossae continuous and not well defined; setose foveae present at each anterolateral angle and at posterior margin in front of mesocoxal cavity (the posterior pair are half the size of the anterior pair), mesosternal process narrow and contacting metasternum. Mesepimeron reaching mesocoxal cavity. Mesocoxae moderately widely separated; mesotrochantin exposed. Metasternum long, length about 2× that of width of mesocoxa, on each side with 3 pairs of setose foveae along anterior margin, one under mesocoxa, the second at lateral angle, the third approximate and smaller in size than the other 2 pairs, located at middle between mesocoxal cavities; submesocoxal line or bead poorly developed; transverse premetacoxal line present, discrimen absent. Metepisternum with pit at medio­anterior angle. Elytral punctuation seriate, more or less in regular rows; sutural stria absent; epipleuron incomplete. Abdomen with 5 visible sterna; ventrite 1 longer than combined length of ventrites 2– 4, lacking subcoxal lines but with pair of setose foveae under each coxa. Trochanterofemoral attachment oblique. Tibiae lacking spurs. Tarsal formula 4–4– 4 in both sexes; tenent setae present on pro­ and mesotarsomeres of male; tarsomeres 1 and 2 short, slightly lobed below, tarsomere 3 short but visible in ventral view; tarsomere 4 long, about 1.5× longer than 1–3; tarsal claw without tooth. Hindwing with venation reduced, anal lobe present. Male abdominal segment 9 separated into two lobes ( Fig. 3 ). Aedeagus with median lobe rather long, sclerotized, markedly curved ( Fig. 2 ); tegminal strut present. Gonocoxites relatively broad, lacking gonostyli. Spermatheca not observed in the single female dissected.

Comments. The new genus includes two species: one, described in the present paper, that occurs in northeastern North America, and the second one known from Montana, Utah, and Oregon. The western species, of which we have seen four specimens, was first collected by Mike Ivie who is describing it .

The phylogenetic relationships and limits of the 11 subfamilies of Endomychidae are unresolved and it is likely that many of the current family­groups are paraphyletic (Ślipiński and Pakaluk 1992; Tomaszewska 1999). Therefore the exact placement of Hadromychus in the classification of Endomychidae is preliminary at best. Among the typically ‘‘small­bodied’’ endomychids, the elongate body shape and 11­segmented antenna will exclude Hadromychusfrom the coccinelloid group Anamorphinae , the 3­segmented antennal club will separate it from Holoparamecinae , presence of open procoxal and mesocoxal cavities will exclude it from Acritosomatinae, absence of a chin piece (anterior lobe) arising from the prosternum and absence of subcoxal lines on ventrite 1 will exclude it from Eupsilobiinae , and the fact that the pronotal sublateral carina is not continuous along the anterior edge of the pronotum in Hadromychus will exclude it from Mycetaeinae and Agaricophilus .

Among the ‘‘large­bodied’’ groups, members of Pleganophorinae differ from those of Hadromychus by the modified segments of the antennae in both sexes, wide and flattened galea, and lack of foveae on ventrite 1. Hadromychus is somewhat intermediate between the subfamilies Epipocinae and Leiestinae , and shares some character states with Xenomycetinae (Xenomycetes) : the presence of seriate elytral punctation, reduced prosternal process, and slightly lobed tarsomeres 1 and 2. Xenomycetes differs from Hadromychus by several character states, including exposed antennal insertions, a thick bead on the margins of the pronotum, markedly developed anterior pronotal angles, and trochanterofemoral attachment heteromeroid (see Tomaszewska 2000: Table 1). These character states also distinguish Hadromychus from Lycoperdoninae and Endomychinae along with the presence of dorsal vestiture of setae and slightly lobed tarsomeres 1 and 2.

Hadromychus chandleri is very similar to Danascelis elongata that Tomaszewska (1999) described and placed in the subfamily Epipocinae as a relative of Danae and Tragoscelis Strohecker. Hadromychus shares many character states with Danascelis , including the hidden antennal insertions [though Tomaszewska (1999) mentions that the antennal sockets are partially visible from above], swollen antennomere 9 of male, paired foveae on each side of the pronotum, lack of a thick basal bead and sublateral sulci on the pronotum, unicarinate mesosternum, absence of metasternal discrimen, absence of a sutural stria on elytron, and slightly lobed tarsomeres. Danascelis differs from Hadromychus by several character states, though, including the following (according to Tomaszewska’s description and figures): antennomere 9 of male with a patch of long setae, prosternal process wider, mesosternum without small fovea just in front of each coxa, ventrite 1 with only two subcoxal foveae, male segment 9 lacking paired lobes, and hindwings reduced. Hadromychus differs from the remaining Epipocinae (including Periptyctus , which lacks laciniae and has a chin piece) by the striate elytra and the slightly lobed tarsomeres, suggesting that Hadromychus and Danascelis may not be members of this subfamily.

Danascelis and Hadromychus may be related to Leiestinae because all of these taxa have the antennal insertions hidden in dorsal view, a feature that is not present in most other groups of Endomychidae . Additional features that suggest Danascelis and Hadromychus have affinities with Leiestinae are the reduced prosternal process, slightly produced anterior pronotal angles, and slightly lobed tarsomeres 1 and 2. We note, however, that members of Leiestinae possess several features that are lacking in Danascelis and Hadromychus such as a deep lateral longitudinal sulci on the pronotum, a trochantinal notch on the prosternum, a bicarinate mesosternum, the concealed mesotrochantin, and absence of hindwing anal lobe ( Tomaszewska 2000). Moreover, some of these characters are variable within endomychids and without a phylogeny for the entire family, our placement of Hadromychus and Danascelis is speculative. At present, we prefer to follow Tomaszewska (1999) and leave the two genera in the subfamily Epipocinae .

In the conclusion of his discussion on sexually dimorphic features in endomychids, Arrow (1925:277) noted that ‘‘the whole of these various secondary sexual features must be regarded as without known significance in the present scanty state of our knowledge.’’ Though direct observations are lacking, these characters may provide clues about the behavioural complexity of Endomychidae , and can be grouped into two classes: structures associated with chemical communication and those associated with courtship while the sexes are in physical contact. Spines, teeth, notches, and modified processes on the legs and ventrites of many Endomychidae (e.g., Arrow 1925; Strohecker 1953; Leschen and Carlton 1993, 2000; Tomaszewska 2000) are probably used by males for either securing females during copula or stimulating females during mating.

The swollen ninth antennomere in the male of Hadromychus is also characteristic of males of Danascelis , Tragoscelis , some species of Danae , and Pseudindalmus Arrow , while all of the antennomeres of the club are modified in male Phymophora ( Arrow 1925; Strohecker 1953). The large surface area of the antennal cuticle, like members of Pleganophorinae , may be invaginated and is covered with conical sensillae. While Pleganophorinae may be producing large quantities of appeasement pheromones in nests of social insects, males of the dimorphic species, such as Hadromychus chandleri , may be producing pheromones for enhancing female responses during mating. On the other hand, the modified antennae may be used for locating potential mates via pheromones, though well developed cuticular glands have not been identified in females.

Figures

Figs. 2–3. Hadromychus chandleri Bousquet and Leschen. 2) Median lobe of aedeagus; 3) ninth abdominal segment of male.