Identification: Current status of New World taxonomic resources

A list of works to identify North American delphacids is provided through the link to the right.
The published literature on the identification of New World delphacids is problematic.   There are a variety of resources that are useful for identifying the species within many delphacid genera, particularly for the species north of Mexico (see list here), but very limited resources to assist in the identification of genera.  Also, while some genera have been revised with consistently defined species and diagnostic resources, other genera – including some common ones – have limited diagnostic resources or have never been revised.  Within the genera that have not been revised, a surprising number of species are misplaced at the generic level.  Misplaces species complicate the development of diagnostic keys, since they do not possess all the features usually attributed to the genus they purportedly represent (this has occurred partly because generic concepts have changed over time).  Finally, some species are obscure and poorly described, so that confident identification requires comparison with an authoritatively identified specimen, if not the type specimen.  It is this series of difficulties that the identification resources of this website are intended to address.

The most useful modern identification tools for delphacids to genus are those of Wilson (2005) to economic species, Wilson and McPherson (1980a) for Illinois (16 genera, 65 species), Wilson (1988, 1992) to Alaska and the Yukon, and Caldwell and Martorell (1951) to Puerto Rico (which is helpful for the Caribbean and Central America).  The most recent comprehensive catalog is Metcalf (1943), which treats the world fauna, but in the New World 39 of 93 genera (42%) and 142 of 551 species (26%) have been described since the catalog was published (see Figure).  There are no generic keys to any broad geographic area (larger than state) since the antiquated Muir & Giffard (1924), Metcalf (1923), and Crawford (1914) (although keys to North American planthopper genera have been developed, Bartlett et al. in prep.).  Adequate keys do exist to species of relatively distinctive genera, but not Delphacodes, Nothodelphax, Euides, or Javesella.  There are no keys to the fauna of Central or South America, except parts of the Argentinean fauna (de Remes-Lenicov & Teson 1978, 1979a, b; Teson & de Remes-Lenicov 1983, 1989; de Remes-Lenicov 1993, 1996; Mariani & de Remes-Lenicov 2001).  (The Argentinean work, while providing good tools for species recognition, has made no attempt to address doubtful generic constructs, esp. Delphacodes, Dicranotropis and Euides)  The only major work on the Neotropical fauna was Muir (1926), which treated 25 genera and 85 species (67 new) from the then known fauna of 31 genera and 114 species from South America (now 47 genera and 160 species south of Panama), but presented no keys.  The Central American species have never been reviewed, except those that occur within the fauna of Puerto Rico (Caldwell & Martorell 1951).

Numerous species of New World delphacids are doubtfully placed, or clearly misplaced, at the generic level.  Asche (1985: 309) considered 206 New World species (i.e., approximately 37% of the fauna) to be incertae sedis in their generic placement.  The polyphyletic Delphacodes is a major culprit.  Although there are 134 New World species, most workers consider Delphacodes an Old World genus of 10 species (e.g., Wagner 1963, Asche & Remane 1982, Asche 1985, Holzinger et al. 2003).  Similarly, all New World members of the genera Aeropus, Asiraca, Chloriana, Columbisoga, Delphax, Dicranotropis, Euides, Eurysa, Kormus, Liburnia, Malaxa, and Sogata (collectively 186 species, 34% of the New World fauna) are improperly or uncertainly placed at the generic level. 

On the other hand, many New World delphacid genera have modern revisions, at least for those species North of Mexico.  Many of these genera are “easily” recognized with modest experience.  Here is a table listing available taxonomic resources pertinent to New World delphacid taxa.