Echo Selys 1853
Creators: name: Orr, Albert G. W.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Odonata
Calopterygidae
Echo

description: Echo
The genus includes five species ranging from southern China and the eastern Himalayas to the Malay Peninsula and Sumatra. Only the larva of Echo uniformis Selys from Sumatra has been briefly described and illustrated (Lieftinck 1965, van Tol 1992), with drawings showing the habitus and the prementum with labial palps. Nevertheless, both illustrations and the brief text convey critical information that separates the genus from any other, including its sister genus Psolodesmus (according to Dumont et al. 2007), which is confined to Taiwan and southern Japanese Islands. The prementum (Fig. 33) is very similar to that of Psolodesmus, but has two setae on the anterior lobes of the prementum (one in Psolodesmus). Both genera have a similar robust build (Fig. 56). Also in Psolodesmus the short outer, triquetral caudal gills bear very strong teeth along the outer central ridge but not on the dorsal and ventral margins, whereas in E. uniformis all three ridges bear dentition, according to Lieftinck’s (1965) text, and illustration. The larva of E. modesta Laidlaw has been collected on Langkawi Island, Malaysia (S.G. Butler pers. comm.), and, an F- 1 specimen was collected by AGO in a leaf pack in a very small and shallow rocky branch of a small forest stream in Kanchanaburi, Thailand in 2003. Adult E. modesta were present and no other species with which the larva might be confused occurs in the area. The species has also been bred, but not yet described (T.S. Keetapithchayakul pers. comm.), confirming the above identifications. Both specimens have strong dentition dorsally and laterally on the margins of the caudal gills as well as lighter denticulations on the outer central ridge (Fig. 43); the central gill, which is almost as long as the lateral ones, has dorsally at its base a broad triangular sclerotised and slightly serrate guard plate for about one third its length, which is also well developed on E. uniformis. The other genus in which the prementum is similar is Mnais, but as in Psolodesmus it differs in bearing only one pair of setae on the lobes of the prementum. In addition the known larvae of Mnais are less heavily built and the margins of the outer caudal gills are smooth, without dentition, and usually longer and narrower.
Nevertheless, in southern China there is a distinct possibility that species of Echo and Mnais may overlap (Zhang 2019), and it is unclear if any of those Echo species (E. candens Zhang et al., E. margarita Selys and E. perornata Yu & Hämäläinen) have the same larval form and same distinguishing characters as E. uniformis and E. modesta, or indeed, if all Mnais species differ in the way we presently recognise. A possible hint as to the differences we may expect has been suggested (Orr & Butler 2024), but until we have certified voucher specimens, this question remains open.
description: Published as part of Orr, Albert G. W., 2024, A review of present knowledge of larvae of the Calopterygoidea (Zygoptera) of the Oriental realm, including keys to families and known genera, pp. 209-243 in Zootaxa 5497 (2) on page 224, DOI: 10.11646/zootaxa.5497.2.3, http://zenodo.org/record/13618317