Decadiomus Chapin, 1933

Vandenberg, Natalia J. & Hanson, Paul E., 2019, Overview of the lady beetle tribe Diomini (Coleoptera: Coccinellidae) and description of a new phytophagous, silk-spinning genus from Costa Rica that induces food bodies on leaves of Piper (Piperaceae), Zootaxa 4554 (1), pp. 255-285 : 263-264

Decadiomus Chapin, 1933

Decadiomus Chapin 1933:96 . Type species: Diomus bahamicus Casey, 1899 , by original designation.

Diagnosis. In the New World fauna, Decadiomus species can be distinguished from most previously known Diomini by the combination of: antenna composed of 10 antennomeres, prosternum shaped like a short stemmed Y, short anterior to coxal cavities (about ½ diameter of cavity), intercoxal process with carinae extending to anterior margin or nearly so.

Decadiomus differs from the new genus described in the present paper (which also has only 10 antennomeres) by having free living, predatory larvae, and also by characteristics of the male genitalia: penis with apical flagellum ( Fig. 7 ), and outer arm of capsule truncated or strongly reduced and not enclosing the ejaculatory duct prior to its entry into the main penis tube ( Figs. 11–12 ).

Genital characteristics of Decadiomus males and females are included in the generic key, below, and also discussed by Gordon (1976) (as Diomus, floridanus group and bigemmeus group), and by Segarra-Carmona and Otero (2014). These characteristics may serve to differentiate Decadiomus species from the occasional occurrence of Diomini with 10 antennomeres from areas outside of the New World (e.g. in some individuals of Diomus flavolaterus (Lea) from Australia).

Remarks. The following species previously classified in Diomus are hereby transferred and represent new combinations within Decadiomus : D. balteatus (LeConte, 1878) , D. floridanus (Mulsant, 1850) , D. amabilis (LeConte, 1852) , D. liebecki (Horn, 1895) , D. myrmidon (Mulsant, 1850) , D. humilis ( Gordon, 1976) , D. pseudotaedatus ( Gordon, 1976) , D. taedatus (Fall, 1901) , D. bigemmeus (Horn, 1895) , and D. austrinus ( Gordon, 1976) . Decadiomus seini Segarra, 2014 is placed as a junior synonym of D. austrinus based on the original type descriptions and illustrations, and a comparison between specimens from Puerto Rico and the type material of D. austrinus .

Figures

FIGURES 3–12. Genitalia of Diomini and Selvadiina (Hyperaspidini): 3–6, female genitalia, dorsal view (spermatheca shaded gray): 3, Selvadius nunenmacheri Gordon 1970 (Hyperaspidini: Selvadiina), showing distal end of sperm duct and spermatheca, accessory gland not shown (after Gordon 1985); 4, Erratodiomus brindisi Gordon 1999 (Hyperaspidini: Selvadiina), bursa through spermatheca, accessory gland not shown (after Gordon 1999); 5, Decadiomus hughesi Gordon & Hilburn 1990 (Diomini), bursa through spermatheca (note long convoluted sperm duct); 6, M. lachesis (Diomini) (A.g.= accessory gland); 7–12, male genitalia of Diomini, left lateral view of penis: 7, D. hughesi; 8, M. lachesis; 9, Diomus donatus Gordon (capsule); 10, M. lachesis (capsule); 11, Decadiomus bigemmeus (capsule); 12, Decadiomus liebecki (capsule)