Dineutus serrulatus LeConte, 1868

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 : 66-67

Dineutus serrulatus LeConte, 1868

Differential diagnosis.

Overall this species can be diagnosed in having elytral apices that are serrulate and with apicolateral sinuation present in both sexes, red colored venters, males with a profemoral sub-apicoventral tooth, and in the form of the male aedeagus. A key to the subspecies is provided and each subspecies is treated individually.

Distribution and subspecies.

This species is wide-ranging, highly variable among populations (Fig. 39), and has been divided into two subspecies: Dineutus serrulatus serrulatus and Dineutus serrulatus analis ( Wood 1968). Of these subspecies Dineutus serrulatus serrulatus is more consistent in its characters, while those of Dineutus serrulatus analis are much more variable causing difficulties in separating the two. Dineutus serrulatus analis was originally described as a separate species by Régimbart in 1882, but was relegated to a subspecies of Dineutus serrulatus LeConte by Wood (1968). Recent papers have again treated Dineutes analis as a separate valid species (e.g. Ciegler et al 2003; Realzola et al. 2007). For this study the authors found no single discrete character that could reliably separate the taxa. Although dorsal coloration can usually be used to separate the two subspecies, populations from northern Florida where the two subspecies meet, show intermediate dorsal coloration, being medially polished black, but laterally bronzy green. Furthermore the aedeagi, of the two subspecies are very similar, with only minor differences that appear variable across the entire range of this species. Another useful character for delimiting similar species, the mesotarsal claws, are also similar showing only minor variation. For these reasons we continue to follow Wood (1968) in treating these two taxa as subspecies.

Key to the subspecies of Dineutus serrulatus

1	Body form more broadly oval, especially evident in males (Fig. 40C); male elytra with apices often flatly rounded/subtruncate, rarely with sutural angle produced to a point, apicolateral sinuation strongly present; female elytral apices flatly rounded and commonly with sutural angle produced, apicolateral sinuation less strongly present; dorsal surface with fine reticulation giving the dorsum a more polished smooth appearance, often very darkly colored, black to dark greenish black; profemoral sub-apicoventral tooth of male large and highly acute (Fig. 40D); venter always red in coloration. Distribution: Alabama, Georgia, Florida, and the Carolinas	Dineutus serrulatus serrulatus
-	Body form more parallel sided, less broadly oval, even in males (Fig. 40C); males with elytral apices variable from flatly rounded/subtruncate, but often with sutural angle produced, apicolateral sinuation present, but less deeply sinuate; female elytral apices flatly rounded to angled towards sutural production; sutural production commonly present, rarely absent; dorsal surface with reticulation strongly evident and often coarser than nominate form, giving dorsal surface a bronzy appearance, not polished black, often light bronzed to greenish bronzed in color; profemoral sub-apicoventral tooth often smaller than nominate form (Fig. 40D), and more variable; venter often light colored usually red, but northern and western populations with darkly colored venter, dark red to blackish red in coloration. Distribution: From western Alabama north to Indiana, west to southwestern Kansas, south to Texas and possibly Mexico	Dineutus serrulatus analis