Protallagma Kennedy, 1920

Hunger, Holger & Schiel, Franz-Josef, 2012, Description of Protallagma hoffmanni sp. nov. from the Peruvian Andes (Odonata: Coenagrionidae), including description of its larva, Zootaxa 3202, pp. 28-50 : 46

Differentiation between Protallagma Kennedy, 1920 and Oxyallagma Kennedy, 1920

The genus names Protallagma and Oxyallagma were both introduced by Kennedy (1920). Protallagma was applied to the type of Amphiagrion titicacae ( Calvert 1909) , a species also bearing the synonym Protallagma andinum ( Förster, 1909) . The genus Oxyallagma was applied to Oxyagrion dissidens ( Selys, 1876) . However, the differentiation between the genera Protallagma and Oxyallagma posed some difficulties in the past. In 1939, Kennedy received more than thousand specimens of a red and blue damselfly from Ecuador which he considered a new Protallagma species. He described it as Protallagma runtuni ( Kennedy, 1939) , but later ( Kennedy, 1946) recognised it was identical with Oxyallagma dissidens ( Selys, 1876) . Thus, both genera remained monospecific.

Protallagma and Oxyallagma have indeed many similarities at first sight, but apart from Protallagma being more compact and sturdy than the comparatively slender Oxyallagma , and different patterns in the red and blue coloration of the abdomen, there are several clear characteristics setting them apart:

1. The first and clearest trait is the different shape of the male appendages. Kennedy (1939: 184) states that the upper appendages of both genera are “mitten-shaped” seen from the side—suggesting relationship to the genus Enallagma . While the downward-pointing ventro-apical process or “thumb” of the “mittens” of P. titicacae is small—it is much more pronounced in P. hoffmanni —it is even smaller in Oxyallagma dissidens , however, making it hard to describe the cerci as “mitten-shaped.” In O. dissidens , there are in fact two ventro-apical processes in the cercus, visible in mediodorsal or medial view ( Garrison et al. 2010: 305, Fig. 1972), whereas only one is present in P. titicacae ( Garrison et al. 2010: 310, Fig. 2007). In Oxyallagma , it is rather the paraprocts that resemble a mitten with a stout “thumb” pointing upward.

2. A second trait can be found on the pronotum: The edge of the pronotum hind lobe of males of O. dissidens is almost perfectly straight and thus different from both P. titicacae and P. hoffmanni . The female pronotum of Oxyallagma is different from both Protallagma species as well.

3. The apex of S10 of both Protallagma species lacks the pair of small tubercles present on the posterior margin of S 10 in males of O. dissidens (see also Kennedy 1920: 86; Kennedy 1946: 184; Garrison et al. 2010: 305, 310, Figs. 1973, 2007).

4. This trait applies to both sexes and is also described and depicted in von Ellenrieder & Garrison (2009: 130) and Garrison et al. (2010: 309–310, Fig. 2000): the venter of the thorax bears a “mound-like medial tubercle” in Protallagma . This tubercle, which also exists in Protallagma hoffmanni , is much shallower in Oxyallagma .

5. The distal segment of the genital ligula in Oxyallagma has no inner fold proximal to the flexure but does have an inner transverse membranous fold bearing an inner process distal to the flexure, and one lateral lobe on each side ( Garrison et al. 2010: 305, Figs. 1969–1970), whereas in P. titicacae ( Garrison et al. 2010: 310, Figs. 2005, 2006) and P. hoffmanni ( Figs. 5–6 ) it has an inner fold proximal to the flexure, no inner transverse membranous lobe distal to the flexure, and two lateral lobes on each side.

6. A pale occipital bar ( Garrison et al. 2010: 309) is present in both P. titicacae and P. hoffmanni .

7. Another trait, which may not have been mentioned in the literature, is that the pterostigma of both Protallagma species is clearly narrower than the comparatively elongate pterostigma of Oxyallagma dissidens .

These characteristics lead to the conclusion that the new species belongs to the genus Protallagma .

Figures

FIGURE 5. P. hoffmanni, genital ligula, taken from paratype, lateral view.