FNZ 40 - Cixiidae (Insecta: Hemiptera: Auchenorrhyncha) - Introduction
Larivière, M-C 1999. Cixiidae (Insecta: Hemiptera: Auchenorrhyncha). Fauna of New Zealand 40, 93 pages.
(
ISSN 0111-5383 (print),
;
no.
40.
ISBN 0-478-09334-9 (print),
).
Published 12 Nov 1999
ZooBank: http://zoobank.org/References/E2254530-A9D1-4427-9AD2-A70716D7F95D
Introduction
The family Cixiidae is cosmopolitan, with over 1500 described species that may represent about 40 percent of the actual world fauna. The present faunal review records 11 genera and 25 species for New Zealand. This should constitute the near totality of the fauna; a few additional cave-dwelling species may still be discovered.
Compared with New Zealand, the Australian fauna remains largely unknown, with only about 40 species described, of which several are currently placed in the cosmopolitan genus Oliarus Stål.
The present work offers a concise faunal review of the New Zealand Cixiidae, based on the study of adults contained in local and overseas collections. It represents a first modern attempt to bring together the scattered information dealing with the group.
The goals of this review are straightforward: to provide an inventory of New Zealand taxa, a concise treatment of their taxonomy, keys to genera and species, and a summary of the available information on species distribution and biology.
Taxonomic history
There has been little work done on the faunistics of the New Zealand Cixiidae since the beginning of the 20th century. The most comprehensive taxonomic treatment to date is that of Myers (1924) who provided a key to eight genera, descriptions of new taxa (4 genera, 9 species), and comments on most of the 17 species known at the time. A limited amount of study material, mostly types, was available to Myers. As a result, the high degree of morphological variation between and within species may not have appeared as obvious as it is today from the extensive material contained in New Zealand collections. For this reason, it seemed timely to provide a new taxonomic revision for this group, one that includes descriptions and keys that take into account this new information.
Metcalf (1936) was the first to catalogue the New Zealand taxa following Myers' paper. It took about 40 years before another taxonomic paper was published on Cixiidae, i.e., the description of the cave-dwelling species Confuga persephone by Fennah (1975). Subsequently, Wise (1977) published a synonymical list of the New Zealand taxa. Deitz and Helmore (1979) provided an easy-to-follow key to identify Cixiidae from other planthopper families occurring in New Zealand and a key to Cixiidae genera. Larivière (1997a) updated the list of described taxa. Finally, Larivière (1997b) and Larivière & Hoch (1998) resumed work on the taxonomy of these planthoppers by reviewing Koroana Myers and Semo White.
Higher classification
The main contributors to the higher classification of the family include Muir, Metcalf, and Emeljanov. Muir (1922) erected the tribe Oecleini when he described the Malayan genus Euryphlepsia. His subsequent papers (1923, 1925) dividing the family into 2 tribes (Cixiini, including Oecleini, and Bothriocerini) became the basis for most work since. In his catalogue, Metcalf (1936) adopted the classification proposed by Muir (1925), but in 1938 he elevated the tribes Cixiini and Bothriocerini to the rank of subfamilies and created new tribes within each subfamily. His tribal divisions, however, have not been universally adopted by subsequent workers. Emeljanov (1971) separated the tribe Pentastirini, with two subtribes, from Cixiini. More recently, Emeljanov (1989) reviewed the problem of the higher classification of Cixiidae.
There is as yet no rigorous treatment of the classification for the family. Criteria defining supraspecific taxa are still insufficiently elaborated, and phylogenetic (or even cladistic) analyses are practically nonexistent for this family.
The family classification adopted here follows Emeljanov (1989) who recognised three subfamilies (Bothriocerinae, Borystheninae, and Cixiinae). Three tribes of Cixiinae have so far been recorded from New Zealand: the Oecleini, represented by Tiriteana [and possibly Confuga (see Fennah 1975: 379)], the Pentastirini, represented by Oliarus, and the Cixiini, represented by all other genera.
Emeljanov (1997) presented a tentative cladogram of Cixiidae tribes, in an attempt to evaluate the usefulness of certain characters to reconstruct phylogeny. He suggested that Semo could be placed in a separate tribe, the Semonini, together with the mainly Oriental genera Kuvera and Betacixius, on the basis of having a swollen postclypeus. Emeljanov made it clear, however, that his attempt to distinguish the tribes of Cixiidae was made on precarious bases; he did not intend to propose a formal classification. Therefore, the present revision follows Larivière & Hoch (1998) in adopting the traditional placement of Semo within Cixiini.
Morphological characteristics
Cixiidae have retained a series of plesiomorphic characters distinguishing them from other fulgoroid families, for example, the presence of a third ocellus on the frons in many genera. For this reason they are considered to be one of the most primitive families of planthoppers.
They are characterised mainly by the forewings, which are usually membranous, and usually have tubercles bearing setae (setiferous tubercles) along the veins. Their size generally ranges from 3 to 11 mm and most species hold their wings horizontally, although some hold them vertically. Males have complex genital structures that are partially exposed. The aedeagus is composed of a shaft (periandrium) and a flagellum with a number of processes and appendages. These structures are usually highly diagnostic at the species level. Females have a sword-like or short porrect ovipositor. Figures 1-11 provide a basic understanding of the morphological structures used to identify cixiid genera and species.
Geographical distribution
The New Zealand fauna is highly insular, with 8 genera (73%) and 25 species (100%) presently recorded as endemic. The indigenous genus Aka White has two representatives in Tasmania. The genera Oliarus and Cixius are cosmopolitan.
The overall distribution of New Zealand Cixiidae is summarised in Table 1 and in Maps 13 and 14. Species distributions are clearly defined and largely allopatric. Four genera (Cixius, 3 species; Huttia Myers, 2 species; Parasemo gen. nov., 1 species; Tiriteana Myers, 1 species) are confined to the North Island. The cave-dwelling genus Confuga (1 species) is only known from the north-west of the South Island. Chathamaka gen. nov. (1 species) is endemic to the Chatham Islands.
The great majority of Cixiidae species occur on the North Island, although they are not all restricted to it. Seven species (Aka duniana (Myers), Koroana rufifrons (Walker), Malpha muiri Myers, Semo clypeatus White, S. transinsularis Larivière & Hoch, Oliarus atkinsoni Myers, and O. oppositus (Walker)) also occur on the South Island, mostly in northernmost areas. Oliarus oppositus is widely distributed on both islands.
Seven species (Aka westlandica sp. nov., A. dunedinensis sp. nov., Koroana arthuria Myers, K. lanceloti Larivière, Malpha cockcrofti Myers, Semo harrisi (Myers), and S. southlandiae Larivière & Hoch) occur strictly on the South Island; they represent 50% of species of Aka, Malpha Myers, and Semo, and 67% of Koroana.
Biology
Very little is known about the habits of the majority of New Zealand species, except Oliarus atkinsoni which has been thoroughly studied because it is a known vector of plant disease. Most species appear to have a similar life cycle, with one egg stage, five nymphal stages, and a single generation each year. Oliarus atkinsoni, however, has a two-year life cycle. This is also the only species with described nymphs.
Female cixiids secrete a white woolly wax which is carried at the end of the abdomen and put around the eggs when they are laid in the soil. Nymphs develop around plant roots on which they feed. Adults are mostly active during the day. They are found on trees, shrubs, and amongst grasses, and generally stay on the most sun-exposed parts of their food plants where they can be collected by beating or sweeping. A number of species have been captured at night on low vegetation; this may indicate some degree of nocturnal activity.
In New Zealand, little is known about host plant requirements but there are definite habitat preferences. Most New Zealand cixiids inhabit forested or bush environments, including scrublands and shrublands, from coastal lowlands to the subalpine zone. Observed habitats and altitudinal ranges of genera are summarised in Table 2. The majority of genera are found in lowland to lower mountain mixed podocarp-broadleaf habitats. Information obtained so far on the genus Aka suggests a close association with Nothofagus forests, which may indicate an old lineage. Semo is strictly a subalpine genus with largely allopatric species that are morphologically highly similar. This may indicate relatively recent speciation. The New Zealand alpine zone itself originated in the Pliocene; rapid and continuing speciation has been suggested for the evolution of the alpine biota (Kuschel 1975; Wardle 1991). Koroana is the only genus that spans a broad altitudinal range from lowlands to subalpine environments.
According to world literature, most cixiid species feed on a variety of plants, although some species have been reported to be oligophagous or monophagous. As for nymphs, the majority of records are from grasses (Wilson et al. 1994), but they have also been reported feeding on the roots of ferns (e.g., Zimmerman 1948), gymnosperms (e.g, Pinaceae, Sheppard et al. 1979), other monocotyle-dons (e.g., Agavaceae, Cumber 1952) and a number of dicotyledon families, including Asteraceae (Wilson et al. 1994). For adults, which feed above ground, most host records are from woody dicotyledons (Wilson et al. 1994), but some adult cixiids are reported from ferns (e.g., Zimmerman 1948), gymnosperms, and monocotyledons. Within monocotyledons, most records are from the Poaceae, Arecaceae, and Agavaceae. Most species have been recorded from a single host genus.
Table 3 results from the author's effort to compile a list of potential host plants from the literature, specimen labels, and her own fieldwork. In general, a method similar to Wilson et al. (1994) was used to minimise spurious collection or literature records. The following records were excluded: species collected by general sweeping; species observed but not feeding on the plant; species taken in general surveys in modified ecosystems; and those species whose taxonomic identity (in the literature) was questionable. Records of large numbers of newly emerged adults were deemed more indicative, and feeding records for nymphs were seen as the most reliable.
Similar tendencies to those observed elsewhere in the world can be seen in New Zealand. Most adults have been found on woody dicotyledons, a lesser number in association with ferns, some on gymnosperms, and Oliarus on monocotyledons (mainly Poaceae and Phormium (Phormiaceae; previously in Agavaceae). The only information available for nymphs is for Oliarus atkinsoni which reproduces on Phormium. Information contained in Table 3 will hopefully guide future work on host plant preferences.
Dispersal
When local conditions become unsuitable, certain foreign species migrate long distances, usually at night. This phenomenon has never been reported in New Zealand where species seem to be able to leap or fly only short distances, presumably to escape danger or to move between plants. A tendency for brachyptery does not appear to be as marked as in other fulgoroid families, e.g., Delphacidae, and although genera such as Aka and Chathamaka gen. nov. have forewings that are somewhat shorter than other genera, they have hindwings that are usually fully developed. The author observed a number of individuals of Chathamaka andrei sp. nov. with their forewings welded together and slightly reduced hindwings.
Economic importance
Many species of Fulgoroidea are pests of cultivated plants around the world. Serious direct damage by Cixiidae, however, is rare in New Zealand. The greatest economic importance of Cixiidae is as vectors of phytoplasma plant diseases, e.g., Oliarus atkinsoni, on the New Zealand flax species.
MORPHOLOGY AND TERMINOLOGY
The reader may acquire the elementary knowledge of adult cixiids morphology necessary to identify New Zealand taxa by reference to Figures 1-11. Other accounts of planthopper morphology can be found in O'Brien and Wilson (1985), the morphological terminology of which is generally adopted here in conjunction with that of recent taxonomic revisions (e.g., Van Stalle 1991). The term 'setiferous peduncles' is used to refer to the small tubercles set with setae, found along the forewing veins in the majority of species.
METHODS AND CONVENTIONS
General working methods were the same as explained previously (Larivière 1995); they are not repeated here.
This study is based on the examination of over 4000 adult Cixiidae from over 700 New Zealand localities, and overseas reference material borrowed from the following institutions:
AMNZ Auckland Institute and War Memorial Museum, Auckland.
ANIC Australian National Insect Collection, Canberra, Australia.
ASCU Agricultural Scientific Collections Unit, NSW Agriculture, Orange, Australia.
BMNH The Natural History Museum, London, U.K.
BPNZ B.H. Patrick collection, Dunedin (now deposited in Otago Museum, Dunedin).
CMNZ Canterbury Museum, Christchurch.
FRNZ Forest Research, Rotorua.
LUNZ Lincoln University, Lincoln.
MONZ Museum of New Zealand Te Papa Tongarewa, Wellington.
NZAC New Zealand Arthropod Collection, Landcare Research, Auckland.
SAMA South Australian Museum, Adelaide, Australia
UCNZ University of Canterbury, Christchurch.
For locality records, area codes of Crosby et al. (1998) are listed from north to south and west to east. Each area is followed by collection localities listed alphabetically, with repository acronyms. A list of geographical coordinates for the main localities from which material was examined, is given in Appendix A.
Biological notes are based on an analysis of specimen label data. The native plants associated with New Zealand Cixiidae are listed in Appendix B, along with their family placement.
Very little specific or reliable information on distribution and biology could be found in the New Zealand literature (over 100 papers) which was thoroughly scanned.
The status, depositories, and full label data of all primary type specimens seen (and a summary of label information for secondary type specimens) are cited for each species. In the list of label data, different labels are separated by a solidus (/) and different lines on a label by a semicolon; all other punctuation is as it appears on the label.
Collecting and preparation
Adults of Cixiidae are generally collected by sweeping or beating shrubs and trees and, for some species, the low vegetation. Beating or hand-picking from selected plants, especially host plants, yields invaluable biological information. Eggs and nymphs can be collected when the host plant is known by digging and sifting the soil around the roots of the host plant.
Adults are best preserved dry. Eggs and nymphs are usually kept in 70-75% ethanol. If a molecular study is intended, adults as well as immatures can be kept in 100% ethanol.
Preparation and curation of insects have been fully described by Walker and Crosby (1988). All specimens should be collected with the locality (including area code: Crosby et al. 1998, and geographical coordinates such as latitude and longitude), collection date, collector's name, and ecological data (e.g., general habitat and host plant).
Most features of the external morphology and the male genitalia can be viewed under an ordinary dissecting microscope. It is necessary to relax and dissect male specimens to study their genitalia.
Male genitalia can be dissected as follows. Pinned specimens are warmed for 5-10 minutes in soapy water or hot alcohol (70-75% ethanol). If the abdomen alone is to be used, this can be separated from the rest of the body by inserting a pin between it and the thorax, or, in difficult cases, by first relaxing the whole specimen in hot soapy water. Each specimen or abdomen is transferred to a watch glass half-filled with water (if soapy water was used) or ethanol, and the pygofer (genital capsule) is pulled away from the body using fine forceps and a micro-scalpel (needle tip from a 1.0 ml disposable hypodermic syringe). The pygofer is then warmed in very hot (almost boiling) ethanol for about 5 minutes, then transferred to another watch glass also containing ethanol. The anal tube, genital styles and aedeagus are detached and extracted from the pygofer in this solution, using fine forceps and a micro-scalpel. Dissected genitalia are subsequently stored in genitalia vials containing glycerine, and remounted on the pin below the relevant specimens.
Another method uses a 10% KOH solution to macerate the abdomen. This is done by putting the abdomen in a test tube containing a little KOH solution and by placing the test tube on a hot plate in a beaker containing water to warm up its content for 10-15 minutes (alternatively the abdomen can be left in cold KOH overnight). The rest of the dissection is done in water. This technique may be quicker for routine identification; KOH is a clearing agent that allows the examination of genitalia by transparency. If the purpose of the study is a taxonomic revision, it is preferable to extract the structures contained in the pygofer because they need to be viewed and illustrated in the exact same angle or position.
Taxonomically relevant characters
Detailed investigations of the external morphology, including the tymbal organ and the female abdomen, revealed very few characters that can be useful in species diagnosis. In most genera, species are morphologically similar, and intraspecific variation is high in most characters, e.g., forewing venation, shape and proportion of structures of the head and thorax.
The characters presented in the descriptions are subsets of the totality of adult characters studied, and represent the most important differences between, or variation amongst, closely related taxa. Characters or states of characters not mentioned in the species descriptions are as described in generic descriptions.
Descriptive measurements and counts were taken in the following manner: vertex length measured from tip of basal emargination to apex of vertex; vertex width taken at level of tip of basal emargination; forewing length taken from base to apex; forewing width measured at tip of clavus; body length measured from apex of head to tip of forewing, cited as a range with mean in parentheses.
Characters with the highest diagnostic value at the species level have been illustrated, including the most diagnostic aspects of the male genitalia. Most illustrations provided in this work represent the most commonly encountered state of a character. The user must allow some degree of variation when working with individual specimens, especially in the case of newly emerged adults that may still have a soft cuticle. It is not uncommon to see somewhat distorted genital structures in teneral individuals.
Keys are somewhat artificial. They are intended as an aid to identification, not a statement of the author's opinion on phylogenetic relations. Additional supporting characters (e.g., distribution) have sometimes been included between key couplets to help identification.
Generic concept
A genus should be a monophyletic group composed of one or more species separated from other genera by a decided gap. The phylogenetic framework to study Cixiidae, however, is insufficiently elaborated to test this hypothesis for New Zealand genera. Consequently, existing generic concepts have in general been accepted. In addition, two new genera are proposed for species not fitting the correlated character complex of species included in already described genera. Recognition of these generic taxa provides new hypotheses that will hopefully be tested by future students of the higher classification of Cixiidae; this must be done on a world basis or at least in an Australasian context.
A cladistic analysis, preferably integrating morphological and genetic information, is needed to determine the phylogenetic position of New Zealand genera within the Cixiidae. Only then can an attempt be made to decipher the evolutionary history of the New Zealand taxa, e.g., to confirm or reject the hypothesis that certain genera are Gondwana relicts, to reconstruct the sequence of speciation and colonization events, and to understand their evolution in general or that of their host plant relationships.
Species concept
The species concept used here is biological, inferred from morphological characters (especially male genitalia) hypothesised to constitute barriers to interbreeding and hence to gene flow between the different species (Larivière & Hoch 1998). This is corroborated, when possible, by geographic and biological information, but is not tested by genetic or ethological investigations. This species concept requires the assumption that reproductive (genetic) continuity or isolation among natural populations is evidenced by continuity or discontinuity in characters of external morphology and genital structures provided by the study of population samples.
As generally observed in Fulgoroidea, the most important characters to discriminate Cixiidae species are the male genital structures, particularly the aedeagus. In the majority of New Zealand genera, most external characters (e.g., forewing colour or venation, head or thorax morphology) are found to vary within species, or the range of their variation overlaps with that of closely related species, and for the most part similarities or differences in external morphology are not congruent with the study of genitalia. Accurate species identification is often virtually impossible without an examination of male genital structures. Therefore, in most cases, females can only be reliably identified by association with males. Fortuitously, identification is facilitated by the fact that New Zealand species are largely allopatric.
Taxonomic arrangement
Further study of Australasian Cixiidae is needed before phylogenetic relationships can be hypothesised, hence taxa are treated alphabetically in this monograph.