Dineutus longimanus (Olivier, 1791)

Gustafson, Grey T. & Miller, Kelly B., 2015, The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera, Gyrinidae, Gyrininae, Dineutini), ZooKeys 476, pp. 1-135 : 47-48

Dineutus longimanus (Olivier, 1791)

Differential diagnosis.

This is a very unique Dineutus species, easily distinguished from all other New World Dineutus , by the elytral apices possessing a spine located between the sutural and apicolateral angles. Serrations and irregularities are also present, and the sutural angle is also produced into a short spine. The venter is usually more lightly colored from reddish to yellow.

Distribution and subspecies.

This species is endemic to the Caribbean and represents a bit of a population genetics and Caribbean biogeography problem. The species is currently divided into four subspecies, with each island of the Greater Antilles having its own subpsieces, with the two most unique subspecies being found at opposite ends of the species distribution (Cuba and Puerto Rico). The two subspecies occupying the middle area of the range (Jamaica and the Dominican Republic) are less distinct and seem to form a gradient between the morphologies of the two subspecies at the opposite ends. The aedeagi of three of the subspecies are very similar with only that of Dineutus longimanus portoricensis offering some significant differences. For these reasons we have decided to retain the classification proposed by Ochs (1924, 1926a, 1938) in treating the four forms as subspecies. Future genetic work may shed some light on these issues.

Dineutus longimanus can be distinguished from all other North American species of Dineutus in having the elytral apices spinose with serrations and irregularities present. The subspecies can be separated by the following key:

1	Body form of both sexes evenly elongate oval (Figs 20A, C; 22A, C); Elytra with apicolateral sinuation not evident, at most weakly developed, apical serrations strongly developed as small thorns; Mesotarsal claws with ventral margin rounded and evenly narrowed apically, without a denticle (Figs 21C; 23C); Metacoxae with numerous shallow punctures extending on to lateral wings of metacoxae; Median lobe of aedeagus more parallel sided, parameres of aedeagus more narrowly rounded (Fig. 21A; 23A). Western Caribbean	2
-	Body form of males more laterally expanded after basal half of elytra (Figs 24C; 26C); Elytra with apicolateral sinuation moderately to strongly evident, apical serrations more weakly developed especially apicolaterally; Mesotarsal claws with a denticle (Figs 25C; 27C); Metacoxae with sparse and very shallowly impressed punctures; Median lobe of aedeagus weakly constricted medially, parameres of aedeagus more broadly rounded (Figs 25A; 26A). Eastern Caribbean	3
2	Relatively smaller in size: 10.8-12.9 mm. Reticulation of dorsal surface more well impressed, medial disc reticulation composed of small regularly shaped circular sculpticells; Metacoxae with numerous large, shallow punctures present, extending regularly on to the metacoxal wings. Cuba	Dineutus longimanus cubensis
-	Relatively larger: 12.1-13.3 mm. Elytral reticulation much more finely impressed, reticulation of medially disc very weakly impressed composed of irregularly shaped sculpticells which are more transversely oriented; Metacoxae with punctures more shallowly impressed, decreased in number the metacoxal wings, only present on the posterior half. Jamaica	Dineutus longimanus jamaicensis
3	Dorsally margin of elytra with lateral greenish sheen; metacoxae with punctures more sparse and more shallowly impressed, barely distinguishable; median lobe of aedeagus with narrow dorsal carina at apex, apically less acuminate and more evenly angled apically. Puerto Rico	Dineutus longimanus portoricensis
-	Margin of elytral without lateral greenish sheen; metacoxae with punctures relatively apparent, but still sparse and shallowly impressed; median lobe of aedeagus without dorsal carina, more acuminate apically. Dominican Republic, Haiti	Dineutus longimanus longimanus