Homaesthesis LeConte, 1873

Santos-Silva, Antonio, Nearns, Eugenio H. & Swift, Ian P., 2016, Revision of the American species of the genus Prionus Geoffroy, 1762 (Coleoptera, Cerambycidae, Prioninae, Prionini), Zootaxa 4134 (1), pp. 1-103 : 8-9

On Homaesthesis LeConte, 1873

When LeConte (1873) established Homaesthesis he pointed out: “In Prionus ♂ and ♀ the sensitive surface is reticulate, with fine elevated lines, but in Homaesthesis ♂, the surface is quite uniform. The sides of the prothorax are armed with 3 acute teeth in Prionus , but in Homaesthesis integra and emarginata the apical and basal teeth are obsolete, so that the sides become unidentate.” And he noted on P. palparis : “ P. palparis Say , has the form of Prionus , but the antennae are as in Homaesthesis .” The same appears in LeConte & Horn (1883).

According to Leng (1884): “This genus [ Prionus ] and Homaesthesis constitute the group Prionini , all the species of which resemble one another closely in superficial appearance… The thorax as noted above is tridentate in Prionus , unidentate in Homaesthesis …” Leng (1884) only followed LeConte’s (1873) opinion. In his key to the species of Prionus he separated them into two groups: “Sensitive surface antennae ♂ and ♀ reticulate with fine elevated lines. Antennal joints 12; soles hind tarsi densely pubescent”, leading to P. laticollis ( Drury, 1773) , P. pocularis Dalman, 1817 , P. californicus Motschulsky, 1845 , P. imbricornis ( Linnaeus, 1767) , and P. fissicornis Haldeman, 1846 ; and “Sensitive surface ♂ uniform. Antennal joints 12; soles of hind tarsi concave and sparsely pubescent”, leading to P. palparis Say, 1824 . And, before the key to the species of Homaesthesis , he recorded: “Sensitive surface ♂ uniform; soles of hind tarsi concave and sparsely pubescent; antennae 13–14 jointed.” As it is possible to see, the concept of Prionus both in LeConte (1873) and Leng (1884), differentiated this genus from Homaesthesis only by the shape of lateral sides of prothorax. As LeConte (1873), Leng (1884) wrote on P. palparis : “The tables are exhibited in the above form for the purpose of clearly showing the close relation between the genera, and also the intermediate position with palparis occupies.” Thus, for LeConte (1873) and Leng (1884), it is not the texture of the surface of antennomere III that separates Prionus from Homaesthesis , but only the prothoracic shape.

Casey (1912) separated Prionus from Homaesthesis and Prionina in his key: “Antennae having the outer joints sculptured with a longitudinal reticulation of anastomosing raised lines, stout and imbricate (♂) or slender (♀); sides of the prothorax with two acute teeth and an acutely prominent to obtuse or rounded basal angle”, leading to Prionus ; and “Antennae having the surface of the outer joints even and not reticulate with raised lines”, leading to Homaesthesis and Prionina . Homaesthesis was separated from Prionina : “Sides of the prothorax as in Prionus ; antennae (♂) with the joints not sinuate beneath at their apices, 12-jointed; posterior tarsi distinctly shorter and broader than in Prionus and more scantily clothed beneath”, leading to Prionina ; and “Sides of the prothorax rounded, without trace of teeth, except occasionally a small median denticle; antennae (♂) formed as in Prionus , the joints deeply sinuate beneath at their apices or strongly bilobed, closely imbricate, 13- to 14-jointed; posterior tarsi as in Prionus but less padded beneath and with more evident long hairs intermingled”, leading to Homaesthesis . In other words, Casey (1912) saw the main feature separating those genera as the presence of striae in Prionus , and their absence in Homaesthesis and Prionina . There are species currently known (allocated in Homaesthesis ) with sides of prothorax distinctly explanate (as in many species of Prionus ), and without striae on the antennomeres. The inclusion of P. palparis and P. simplex in a different genus ( Prionina ), as proposed by Casey (1912), based mainly in the sides of prothorax, is not coherent. For example, at least in P. simplex , the sides of the prothorax can be as in Homaesthesis (without distinct anterolateral angle). Casey (1912) also affirmed that the antennomeres in Prionina are not sinuate or bilobed, while in Homaesthesis they are. However, both forms are present in Homaesthesis , rendering this feature useless. Regarding the posterior tarsi, they are not as mentioned by Casey (1912) in Prionus palparis , type species of Prionina . There are many species in Prionus with the length of metatarsi similar to that of the true P. palparis , which are not short, although they are broader than usually observed in Prionus . However, the metatarsi are quite short in P. simplex , but they are not broad. The ventral side of the metatarsi of P. palparis and P. simplex is more scantily clothed beneath than usually observed in Prionus , but it is also so in the species of P. ( Homaesthesis ) listed by Casey (1912). The metatarsal spongy pad in species of Prionus (Prionus) is quite different from those currently placed in P. ( Homaesthesis ). For example, in the metatarsomeres of P. californicus , the central glabrous area is narrower and well defined and the setae of the pad are dense and uniform, while in P. emarginatus the central glabrous area is distinctly less defined and the setae of the pad are not dense and uniform. Thus, since the only remaining character to separate Homaesthesis from Prionina is prothoracic shape, and we have specimens of at least one species ( P. simplex ) that can be allocated in both genera, we concluded that Linsley (1962) was right when he synonymized Prionina with Homaesthesis .

Lameere (1912a) considered Homaesthesis a synonym of Prionus [translation]: “Second subgroup.—The antennae do not reach the middle of the elytra in male, and they have 13 or 14 segments, the segments from the third are sinuate or emarginated, forming two lobes; the anterolateral angle of prothorax is erased. This subgroup corresponds to the genus Homaesthesis LeConte, Smiths. Misc. Coll. , VI, 1862, p. 288 [sic].” Only Prionus integer and P. emarginatus were considered in the subgroup. However, antennal length is variable, at least in Prionus emarginatus . The antennae in this species can distinctly surpass the middle of elytra, although usually they only reach or almost reach the middle. As seen above, Lameere (1919) listed Prionina as another synonym of Prionus , but it was Linsley (1962) who synonymized the former with Homaesthesis . To Lameere (1919), Prionina corresponded to his first subgroup of the same group of Homaesthesis in Lameere (1912a) , and included only P. palparis . Thus, to Lameere (1919), Homaesthesis and Prionina belonged to the same group, but they formed different subgroups.

Linsley (1957) considered Homaesthesis as a subgenus of Prionus , but did not provide an explanation of his reasoning. Linsley (1962) included five species in this subgenus: P. (Homaesthesis) emarginatus ; P. (H.) integer ; P. (H.) palparis Say, 1824 , P. (H.) simplex ( Casey, 1912) ; and P. (H.) rhodocerus Linsley, 1957 . Currently, Homaesthesis remains as a subgenus of Prionus .

Homaesthesis encompasses species very heterogeneous in general appearance, sharing two features: the absence of striae on antennomeres, and the spongy pad of metatarsomere not dense and not uniform. Hovore & Turnbow (1984) commented on this: “The number of characters by which Homaesthesis may be distinguished has been reduced by the inclusion of arenarius (possessing strongly produced and reflexed anterior pronotal angles). For the present, the 12 to 14-segmented antennae, with non-striolate poriferous areas will suffice to differentiate all known Homaesthesis from other nearctic subgenera of Prionus .” Actually, the species currently allocated in the other subgenera of Prionus , including non-American species, have striolate antennomeres. However, in some species the striae are slightly marked, and in other they are absent on basal antennomeres, as for example, in Prionus gahani Lameere, 1912 (from China), and P. laticollis [if the descriptions by Linsley (1962) and Chemsak (1996) are accurate]. This suggests that the complete absence of striae on antennomeres is just an extreme condition, present in species that do not form a monophyletic group based on that feature. Regarding the number of antennal segments, we will comment on that feature below, where we comment on the validity of Prionus (Neopolyarthron) . However, we believe it is possible to keep P. ( Homaesthesis ) distinct from P. ( Prionus ), based on the combined presence of two features: absence of striae on antennomeres of males; and spongy pad of metatarsomeres sparse (not dense) and uniform in both sexes.