The larvae of Epigomphus jannyae Belle, 1993 and E. tumefactus Calvert, 1903 (Insecta: Odonata: Gomphidae)

The taxonomic knowledge about immature stages of the insect order Odonata (dragonflies and damselflies) is rather limited in tropical America. Here, the larvae of Epigomphus jannyae Belle, 1993 and E. tumefactus Calvert, 1903 are described, figured, and compared with other described congeners. E. jannyae larva is characterized by 3rd antennomere 1.6 times longer than its widest part; ligula very poorly developed, with ten short, truncate teeth on middle; apical lobe of labial palp rounded and smooth. Lateral margins on abdominal segments (S5–9) serrated, lateral spines on S6–9 small and divergent; male epiproct with a pair of dorsal tubercles at basal 0.66; tips of cerci and paraprocts strongly divergent. The larva of E. tumefactus is characterized by 3rd antennomere 2.3 times longer than its widest part, ligula with 6–7 truncate teeth, apical lobe of labial palp acute and finely serrate. Lateral margins of S6–9 serrate, lateral spines on S7–9; male epiproct with a pair of dorsal tubercles at basal 0.50. Differences with other species were found in 3rd antennomere, lateral spines of S7–9, and the caudal appendages. Epigomphus larvae inhabit small, shallow creeks (1st order streams) where they live in fine benthic sediments. When mature, the larva leaves the water in shady places, climbing small rocks at the water’s edge and metamorphosing horizontally on flat rocks. These new descriptions bring the total number of Epigomphus species with known larval stages to eight; only 28% of the species in this genus are known as larva.


INTRODUCTION
Gomphidae is a cosmopolitan insect family of Odonata (dragonflies and damselflies) with over 980 species (Dijkstra et al., 2013). The family is diverse in streams and rivers, but also has several species that inhabit lentic environments (e.g., ponds, lakes) (Garrison, von Ellenrieder & Louton, 2006). Taxonomically, the adults in this group of dragonflies have been well-studied, although new species are frequently described. In contrast, and similar to most insect groups, the immature stages are poorly known. Garrison, von Ellenrieder & Louton (2006) report 255 species of gomphids for the New World, with only 177 of them known as larvae (69%). This lack of knowledge of the larval stages greatly limits our ability to understand the ecological role of insects in their ecosystems.
The genus Epigomphus is a poorly-known group of gomphids that inhabits small streams and rivers in the neotropics. Epigomphus comprises 28 species (Garrison, von Ellenrieder & Louton, 2006), but only six are known as larvae (larval descriptions in parentheses): E. paludosus Hagen in Selys, 1854 (Martins, 1968); E. echeverrii Brooks, 1989, E. subobtusus Selys, 1878, E. subsimilis Calvert, 1920(all three by Ramírez, 1996; E. hylaeus Ris, 1918(Fleck, 2002; and E. crepidus Kennedy, 1936(Novelo-Gutiérrez, Gómez-Anaya & Smith-Gómez, 2015. In this paper, a detailed description and illustrations of the larvae of E. jannyae Belle and E. tumefactus Calvert are provided, based upon a specimen found emerging at the field, and reared larvae, respectively. Both species have restricted distributions and have been reported from a single country, E. jannyae is endemic to Panama and E. tumefactus to Costa Rica.

MATERIALS & METHODS
Epigomphus larvae were collected in Panama and Costa Rica. Larvae were collected from the stream bottom and transported alive to the laboratory. Individuals emerging in the field were also collected. The male exuvia of E. jannyae was preserved in 96% ethanol while the teneral imago was maintained alive for a couple of days before it died and then preserved in ethanol. A couple of last instars (i.e., F-0) larvae of E. tumefactus were reared until emergence; another two F-0 larvae die and were preserved in ethanol. Emerged adults were identified using original descriptions and comparisons with identified specimens deposited at the Instituto de Ecología, A.C., Xalapa, Mexico.

DISCUSSION
The larva of Epigomphus jannyae is similar to larvae of other described Epigomphus species, although they can be separated by the following features (in parentheses those of other species, including E. tumefactus above described): Integument abundantly granular (not granular but covered with minute, scale-like setae, E. crepidus, E. echeverrii, E. subobtusus, E. subsimilis); third antennomere claviform, 1.6 times longer than its widest part (spindle-shaped, 2 times longer or more than its widest part, E. ; lateral spines on S6-9 obtusely pointed (lateral spines on S7-9 sharply pointed, all other species); extreme tips of cerci suddenly and strongly out-turned (extreme tips of cerci slightly divergent, all other species).
The shape and length/width ratio of the 3rd antennomere and the rounded, smooth tip of the labial palp makes the larva of E. jannyae most similar to that of E. hylaeus. However, they differ by the larger stature of E. jannyae as well as the presence of serrations on the lateral margins of S5-9 and the obtusely pointed lateral spines on S6-9 of this species. Likewise, by the shape and length/width ratio of the 3rd antennomere, the larva of E. tumefactus appears related to crepidus, echeverrii, subobtusus, and subsimilis, differing from all these species by the acute tips of its labial palps. In this last feature it could be related to E. paludosus, according with the drawing provided by Martins (1968).
The descriptions here provided would shed light on the relationship of Epigomphus with other genera of Gomphidae. Several authors have tried to relate Epigomphus to other genera based mainly on adult morphology (e.g., Williamson, 1920), while others have included some larval characters (Carle, 1986;Belle, 1996). According to our present knowledge of the larvae, we think that Carle's (1986) classification best reflects the relationships among the genera that he placed in the subfamily Epigomphinae, excepting the Macrogomphini (Macrogomphus only), whose larvae more resemble those of Carl's tribe Gomphoidini. Epigomphus is probably closely related to the oriental Leptogomphus (tribe Leptogomphini) by the following combination of features: antennae with abundant scale-like setae, dual