The Fulgoromorpha, commonly named planthoppers constitute a large group of phytophagous insects in the order Hemiptera, distributed all around the world. They include currently some 14 000 described species, divided in 30 families, including fossils. It is an old group of Hemiptera knows from fossils since lower Permian some 258 millions years ago and their phylogeny is still not well understood. Etho-ecology of planthoppers is dominated by their interaction with host plants which play a major role. Several groups include the most devastating pests of major agricultural crops throughout the world. Currently, more than 150 various species of planthoppers pertaining to various families were indexed like pests for the first 99 cultures of economic interest (Wilson & O' Brien, 1987).

General Biology, Ecology and behaviour

Interactions of planthoppers with host plants are essential as plants are used not only as sources of food but also as oviposition and mating sites, as shelter and as mean to communicate.

As shelter, host plants secure protection against predators (Spiders, phalangids, Heteroptera Miridae, Nabidae, Veliidae and Mesoveliidae, Coleoptera Coccinellidae and Staphylinidae (Döbel & Denno, 1994), Egg parasitoids (Hymenoptera Mymaridae and Trichogrammatidae) or nymphs and adults parasitoids, Hymenoptera Dryinidae, Diptera Pipunculidae, Strepsiptera (Cronin & Strong, 1994)). But also, host plants provide the tool for planthopper communication. Acoustic signals are transmitted by the substrate on which the insects are moving by a rhythmic and specific drumming of the abdomen. Planthoppers seem only concerned by a close range communication between insects on the same plant or on a group of plants whose foliage is in physical contact. Longer-range communication may not exist (Claridge & Vrijer, 1994). Communication in planthoppers directs the reproductive behaviour.

Planthoppers are generally univoltine (but many tettigometrids, cixiids, delphacids, are bi- or trivoltine). Eggs are laid separately or in groups in, on, or close to the plant (Cobben, 1965). They may be protected by waxy secretions, as in cixiids and some fulgorids, or surrounded with earth (egg case) in some issids (Boulard, 1987). Nymphs of cixiids, kinnarids and hypochthonellids are subterranean, whereas those of achilids and derbids live under bark. Some subsocial systems are known, particularly in tettigometrids, which are then most often ant-attended (Bourgoin, 1997).

Association of planthoppers with their host-plant show strong disparities according to the groups. For instance nymphs of Achilidae and Derbidae are linked to fungi. In Meenoplidae, about 80% of the adults are associated with monocots, whereas 80% of the adults of Fulgoridae and Dictyopharidae are associated with dicots (Wilson et al., 1994). The book of Denno and Perfect (1994) is an important contribution to Fulgoromorpha ecology and management.

As Fulgoromorpha are phytophagous insects, they appear unlikely candidates for a permanent life underground. However, more than 60 species distributed into 5 families are already known to be cavernicolous. All cavernicolous planthopers species belong to taxa which immature stages live close to or within the soil. The habits of these nymphs associated to soil environment seem to be a preadaptation to the cavernicolous life (Hoch, 2002). Many cavernicolous species of Fulgoromorpha display particular reductive or specialized morphological trends and behaviours. Reviews on cavernicolous Fulgoromorpha were published by Hoch (1994, 2002).

An important study about life strategies (host specificity, dispersal, life cycles, ... ) of Fulgoromorpha from Germany was recently published (Nickel, 2003).

Economy: Planthoppers as pests

Species of different planthopper families act as pests of agricultural crops throughout the world. Planthoppers damage plants by ovipositing in plant tissues and by feeding on the phloem, sometimes vectoring a variety of plant pathogens. Cixiidae and Delphacidae are the families with the most prejudicial species. Cixiids are vectors of phytoplasma, mycoplasma, prokaryotes-like belonging to the class Mollicutes, whereas delphacids are mainly virus vectors. These diseases cause serious damage on a great variety of economically important plantations. Planthoppers were considered as one of the significant obstacles to the success of the Green Revolution in tropical Southeast Asia with losses estimated in hundreds of millions of dollars (Herdt, 1987). The rice crop in Asia which feeds 60% of the world, population is particularly damaged by the delphacid Nilaparvata lugens (the rice brown planthopper) which is considered as the most important pest of rice in Asia. Some 150 species of planthoppers from various families are currently directly or indirectly recorded as pests of 99 economic plants (Wilson & O'Brien, 1987).

Planthopper's biogeography

Fulgoromorpha are distributed in all parts of the world but mainly in the tropics, with some species adapted to the deserts and dry areas or even north of the Arctic Circle in Alaska. However this biogeographical diversity is unequal for all the families. For instance, the Tettigometridae are absent from the Nearctic, Neotropical and Australian regions, the Meenoplidae are absent from the New World and nine families (Acanaloniidae, Achilidae, Achilixiidae, Eurybrachidae, Fulgoridae, Gengidae, Hypothnonellidae, Kinnaridae and Nogodinidae) are absent (or with few species) from the Palearctic area. From an historical perspective, biogeograpical scenarios in the Australasian area have been provided for the Lophopidae by Soulier-Perkins (1997, 2000).



Morphological characteristics

Including about 14 000 described species divided in 30 families, planthoppers are generally small insects, varying in size from 3 to 15 mm. Nevertheless, some species of the family Fulgoridae have a body length of about 10 cm and a wingspread of about 14,5 cm. Within the Hemiptera, Fulgoromorpha are easily recognised by the presence of tegulae on the mesothorax, by the pedicel of antenna enlarged, often bulbous and bearing some enlarged placoid sensilla and a particular sensory organ, by relatively elongate midcoxae whose bases are widely separated.

A comprehensive account of Fulgoromorpha morphology can be found in papers by O'Brien & Wilson (1985) and by Carver et al. (1991). More particularly head capsule has been studied by Bourgoin (1986) and their special antennal sensilla by Bourgoin et Deiss (1994); wings and nervation by Fennah(1944), Scherbakov (1981, 1982, 1983), Dworakowska (1988), Bourgoin (1997); male genitalia by Fennah (1945), Bourgoin & Huang (1990); female genitalia by Bourgoin (1993); nymphal characteristics by Yang & Yeh (1994) and Emeljanov (2001).



Fulgoromorpha phylogeny

Monophyly of Fulgoromorpha

Monophyly of the clade is attested by morphological and by molecular evidence as well. Molecular phylogeny based on 18S rDNA nucleotide sequences show strong support for a monophyletic Fulgoromorpha (Campbell & al, 1994, 1995, Sorensen & al, 1995, von Dohlen & al., 1995, Bourgoin & al., 1997, Bourgoin & Campbell, 2002). From a morphological perspective, monophyly of Fulgoromorpha is also well supported by several autapomorphies. Most notably some unique morphological characters strongly support this view: the sensory plate organs of the pedicel, the intracephalic position of anterior invaginations of the pretentorium and the presence of Bourgoin's organ in the antennal pedicel. However, Yang & Fang (1993) using distances based on a phenetic analysis placed the Tettigometridae family in a sister position to Cicadomorpha Membracoidea.

Fossil data have recently been tentatively incorporated into a phylogeny of the order Hemiptera based on molecular and morphological interpretations (Bourgoin & Campbell, 2002). A catalogue of all fossil Fulgoromorpha with notes on Hemiptera classification has recently been published (Szwedo & al., 2004).

Family relationships

Various interpretations based on morphological characters have never fully agreed on the phylogenetic position of Fulgoromorpha families and particularly with the place of the family Tettigometridae. Two main positions have been invoked. The classical viewpoint, which places Tettigometridae as the sister-group of all other Fulgoromorpha, was initially proposed by Muir (1923). He was followed by Asche (1988), who presented an important discussion on this subject. Emeljanov (1990) also placed the Tettigometridae as the sister group of all other fulgoromorphan families and proposed a complete and resolved cladogram of the Fulgoromorpha. The second viewpoint on the affiliation of tettigometrids within Fulgoromorpha was also alluded to by Muir (1930) but without clarification. He considered that Tettigometridae might be a more derived lineage closely affiliated with tropiduchoid families. Such point of view gained recent support with morphological and molecular studies (Bourgoin & al., 1997).

For the other families authors agree more or less for some groupings. However it must be mentioned that only few families have been shown to be monophyletic and very probably all these hypotheses should be modified in the future. A key to Lophopidae genera and their phylogeny was provided by Soulier (1998, 2001).

Selected and Cited References