Enochrus (Methydrus)

Alves, Tayná, Clarkson, Bruno & Lima, Lucas Ramos Costa, 2020, A new species of Chasmogenus Sharp, 1882 and new records of Hydrophilidae (Coleoptera) from Northeastern Brazil, Zootaxa 4763 (4), pp. 579-586 : 583

Enochrus (Methydrus) sp. A

Figs. 9–10 , 15

Material examined. 2♂, 5♀ Brazil, Piauí State, Piripiri Municipality, Cachoeira de Buriti dos Cavalos, 04°25’47.2”S, 41°37’53.0”W, 02. VI.2019 ( CEHJ).

Diagnosis. Medium-sized species (3.26–3.73 mm). Form moderately oval; moderately convex. Head brownish with yellowish area in front of eyes; pronotum and elytra yellowish, except blackish medial area on pronotal disc ( Fig. 9 ). Maxillary palpi with penultimate segment somewhat swollen and flattened on inner face. Dorsal punctation on elytra and pronotum weaker than those on head; systematic punctures on head and pronotum present. Prosternum without carina ( Fig. 10 ). Mesoventral process elevated ( Fig. 10 ). Last abdominal ventrite deeply notched, U-shaped ( Fig. 10 ). Parameres narrowed apically, smaller than phallobase, longer than median lobe, rounded at apex, wider at the base; dorsal lobule rising slightly but distinctly above ventral lobule. ( Fig. 15 ).

Remarks. Based on the morphology of the aedeagus ( Fig. 15 ), the collected specimens resemble Enochrus (Methydrus) costaricensis Short, 2005 described based on a single male from Hamburg Farm, Limoìn Province, Costa Rica. The presented specimens and E. costaricensis shared a unique combination of characteristics within the genus with the dorsal strut of the median lobe almost as long as median lobe but slightly rising above (see Short 2005: Fig. 6 ). However, the specimens differ in diagnostic characteristics as the overall shape of the penultimate maxillary palpomere ( Fig. 10 ), which is not as swollen as described for E. costaricensis . Moreover, the record of E. costaricensis in Piauí would reveal an improbable disjunct distribution.

The collected specimens may represent a new taxonomic unit closely related to E. costaricensis but we were not able to observe enough morphological characteristics to diagnose these specimens as a new species. The current information available on the South American biodiversity of the genus is very old and incomplete. In fact, the taxonomy on Neotropical Enochrus is still hard work. The revision on the Neotropical species is needed since many specimens of the genus are easily found in the field but they are usually hard to diagnose in species level. Many of the known species are similar to each other and differ only in subtle characteristics (Andrew Short, Personal communication). On the other hand, we cannot neglect the existence of these specimens in our fieldwork which would contribute to the hole in the biodiversity knowledge of the genus. Thus, we decide to present the morphospecies here with diagnosis and properly illustrated in order to provide information support and enables future research.

Figures

FIGURES 9–14. Habitus of hydrophilids found in the State of Piauí, Brazil. 9–10) Enochrus sp.: 9, dorsal view; 10, ventral view. 11–12) Helochares (Sindolus) femoratus (Brullé, 1841): 11, dorsal view; 12, ventral view. 13–14) Hydrobiomorpha spatula Bachmann, 1988: 13, dorsal view; 14, ventral view.

FIGURES 15–18.Aedeagus of hydrophilids found in the State of Piauí, Brazil. 15, Enochrus (Methydrus) sp.A; 16, Helochares (Sindolus) femoratus (Brullé, 1841); 17–18, Hydrobiomorpha spatula Bachmann, 1988: 17, ventral view; 18, lateral view.

FIGURES 1–8. Chasmogenus cajuina sp. nov. 1–3) Habitus: 1, dorsal view; 2, ventral view (2a, detail of last ventrite); 3, lateral view. 4) Head in dorsal view. 5) Head in ventral view and prosternum. 6–8) Aedeagus: 6) ventral view; 7, dorsal view; 8, detail of apical half.