-Plant Interactions in

Tropical Environments

Results of the Annual Meeting of the German Society for Tropical Ecology held at Bonn, February 13-16, 1992

Editors: W. Barthlott, C. M. Naumann, K. Schmidt- Loske and K.-L. Schuchmann

Published by Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn, Germany 1993

Cite as: Riede, K. (1993): Abundance differences of phytophagous tropical : the case of forest (: ). In: W. Barthlott, C. M. Naumann, K. Schmidt-Loske & K.- L. Schuchmann (Eds.): Animal-Plant-Interactions in Tropical Environments. Results of the Symposium of the German Society for Tropical Ecology held at Bonn, February 13-16, 1992. Zoologisches Forschungsinstitut und Museum Alexander König, Bonn. pp. 211-218. ABUNDANCE DIFFERENCES OF PHYTOPHAGOUS TROPICAL INSECTS: THE CASE OF FOREST GRASSHOPPERS (ORTHOPTERA, CAELIFERA)

Klaus Riede Institut für Biologie l (Zoologie), Alberstraße 21 a, 7800 Freiburg i.Br, Germany

Zusammenfassung. Während die große Artenvielfalt zahlreicher tropischer Insektenordnungen gut belegt ist, exi- stieren nur wenige Untersuchungen zur Häufigkeit regenwaldbewohnender Arten, die bekanntermaßen sehr sel- ten sind. Man beobachtet beträchtliche regionale Häufigkeitsunterschiede, die am Beispiel regenwaldbewohnender Kurzfühlerheuschrecken (Caelifera) in Tieflandregenwaldgebieten Nordwestamazoniens und Borneos verglei- chend untersucht werden. Verschiedene Arten dieser weit entfernten Standorte zeigen bemerkenswerte morpholo- gische Konvergenzen, die als Anpassungen an das Leben in den Baumkronen gedeutet werden können. Heu- schrecken (Acridoidea) sind jedoch auf Borneo wesentlich seltener als in Amazonien, während Grillen und Laub- heuschrecken (Ensifera) an beiden Standorten eine ähnliche Abundanz aufweisen. Als mögliche Ursachen hierfür kommen sowohl die unterschiedliche Architektur der Kronenregion als auch eine geringere Zahl geeigneter dico- tyledoner Futterpflanzen auf Borneo in Betracht. Summary. While increased species diversity of most tropical groups is a well-established fact, Information about their abundance is scarce and it is common knowledge that most species are extremely rare One observes considerable interregional abundance differences which were analyzed by comparing population sizes of lowland rainforest grasshoppers (Caelifera) in Northwest Amazonia and Northeast Borneo. Forest grasshoppers from both sites show remarkable convergences with respect to morphological adaptations for life in the canopy, despite con- siderable geographic and systematic distance. Acridid grasshoppers are much rarer in Borneo than in Northwest Amazonia, while the abundance of long-horned grasshoppers (Ensifera) is similar at both sites. It is hypothesized that different canopy architecture and a lower number of palatable dicotyledonous food plants limit abundance on Borneo. Key words: Amazonia, Bomeo, herbivory, abundance, nutrition ecology, Orthoptera, grasshoppers.

INTRODUCTION reach here in months of unremitting search. In birds there is the same difference ... Yet, along It is generally accepted that there is a huge num- with this poverty of individuals and of species, ber of scientifically undescribed tropical insect there are in almost every class and order some species, though the dimension of our ignorance one or two species of such extreme beauty or is still a matter of debate (cf. Stork 1988). Increas- singularity, äs to vie with, or even surpass, ed diversity is coupled with low abundance and anything that even South America can produce." patchy distribution of most insect populations in These remarks seem anecdotal, but sum-marize tropical rain forests (cf. Elton 1973). For exam- long years of collector's experience Even today, ple, Central Amazonia is well-known for its ex- because of different sampling methods employed tremely low animal biomass due to mineral defi- at different sites, only very few studies allow a ciency (Fittkau 1985). Scarcity and considerable comparison of insect abundance in different regional abundance differences of butterflies and tropical regions (cf. Elton 1973). Conse-quently, birds were already observed by Wallace (1869): the comparative study of herbivore load has been "The few days I stayed here [Batachian, Moluk- tackled from the plant side by measur-ing leaf ken] produced me several new insects, but scarce- damage (Wint 1983). This study reveals a ly any birds. Butterflies and birds are in fact striking similarity of leaf damage levels of remarkably scarce in these forests. One may around 12 % in Papua New Guinea and Panama, walk a whole day and not see more than two or mainly due to phytophagous insects. However, it three species of either. In everything but beetles is evident that there should be considerable these eastern islands are very deficient compared regional differences with respect to the species with the western (Java, Borneo, &c.) and much composition of the herbivore guild. For exam- more so if compared with the forests of South ple, in the Neotropics leaf-cutting ants alone are America, where twenty or thirty species of but- the top consumers (mammals included) of phy- terflies may be caught every day, and on very tomass, consuming 12—17 % of the total leaf pro- good days a hundred — a number we can hardly duction (Cherrett 1986).

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The following reflections on factors affecting collectors, and two decades ago their poor phytophagous insect populations were stimu- representation in museum collections and the lated by the observation of noteworthy abun- ongoing reductions of their habitat were the dance differences of short-horned grasshoppers main reasons for Descamps (1970) to call for an (Caelifera) at a Neotropical and a Paleotropical increased collecting effort. Since then, our lowland forest. Caelifera are exclusively phyto- knowledge of Neotropical TFGs, though still in- phagous throughout all larval stages, in contrast complete, improved considerably, especially after to their omnivorous or carnivorous orthopteran the discovery of grasshoppers from the most in- sister group, the Ensifera (long-horned grasshop- accessible forest stratum, the canopy (Roberts pers: crickets and katydids). For temperate zones 1973; Descamps 1976). In contrast, the TFG holds that Ensifera dominate bushy or woody fauna of the Paleotropics is still poorly known. areas, while principally graminivorous Caelifera dominate in grasslands or savannahs (Schmidt 1987). This is no longer true in tropical forests, STUDY SITES where a considerable number of grasshopper The following observations of grasshopper abun- species feed on both mono- and dicotyledonous dance were made during studies on the beha- plants and inhabit all strata of forest habitat vioural ecology of forest grasshoppers in North- (Table 1). However, tropical forest grasshoppers west Amazonia (NWA) at Ecuador (San Pablo de (TFGs) have never been an esteemed prize for Kantesiya, Prov. Sucumbios, lat. 0°15'S, long. 76°27"W, 300 m altitude) and in South-East Asia (SEA) at Northeast Borneo, Malaysia (Poring, TABLE 1. Species numbers and abundance of SEA and Sabah, South East slope of Mt. Kinabalu; 500 m Neotropical grasshoppers (Acridoidea): Species altitude). Both study sites are characterized by numbers reflect the state of knowledge from 1970. tropical lowland forest (for habitat descriptions "Savannah grasshoppers" comprise subfamilies see Riede 1987 for the NWA, Stein 1978 for the Gomphocerinae, Acridinae and Truxalinae which have not succeeded in colonizing forest habitats, in contrast North Borneo site). Conspicuous colouration to "others" which recrute forest forms, the largest sub- together with a diurnal life style and an imaginal family being the artficial assemblage of "Catan- size of at least l cm makes TFGs comparatively topinae". easy to census by scanning the Vegetation careful- ly with binoculars. Canopy forms were observed Abundance is given äs number of individuals per tree from platforms or walkways and searched for at or number of individuals in secondary formations of 500 sqm. Data from various authors: ' regrouped after logging operations. Descamps 1970, 2 Amedegnato & Descamps 1980, Field observations were complemented by a 3 Stork 1991, * own observations. Further details see study of Bornean museum material at the collec- text. tions C. Willemse (Maastricht), Sarawak Mu- seum (Kuching) and material from a collecting South -East . . -T . expedition of F. Siegert in 1986. In addition, the Neotropis Asia r profound studies of Amedegnato & Descamps (1980) on the composition of Amazonian TFG number of species 1 communities and results from fogging opera- (Acridoidea) 930 821 tions at Celebes (Project Wallace: Butlin & % savannah grasshoppers Monk 1990) and Borneo (Stork 1991) were (Gomphocerinae, Acridinae) 18 % 28 % evaluated. % others (mainly "Catantopinae") 82 % 72 % NEOTROPICAL FOREST GRASS- Abundance HOPPERS forest canopy 6—18 0,6 ind./tree 2 ind./tree 3 A surprising number of species and genera new to science has been discovered by collecting in secondary formations freshly felled trees (cf. Descamps 1976; Riede (500 sqm forest gaps) 2 1990 a). This canopy grasshopper fauna is espe- — minimal (7-yr, Cecropia) 9 ind. 0* — maximal (21-yr) 367 2 ind. 6 4 cially species-rich and abundant in West Amazo- nian lowland forests, but impoverishes towards

212 the East (Amedegnato & Descamps 1982). Many tions. Especially in the latter certain species species are characterized by a vivid colouration, showed increased abundance, probably due to the stout body form, contrasting colouration of hind increase of food plants at certain successional femura and prolonged hind tarsae (Fig. 1). Stri- stages. For example, in a 3 year old field of 0.5 ha dulation is absent, but functional tympana are small populations of Galidacris variabilis, each present (Riede et al. 1990). Protuberant eyes and consisting of 3 and 10 individuals of different lar- characteristic hindleg movements indicate the val stages, could be found on each of its food importance of intraspecific optical communica- plant (Potomorphe peltata (L.); Piperaceae). In- tion (Riede 1987). Besides these "dendrophilous" terestingly, this species accepts a much wider grasshoppers, Descamps (1976) differentiates a variety of food plants in captivity which indi- variety of other ecological types. A rieh fauna of cates that other factors like plant architecture "thamnorhabdophilous" species inhabits shrubs might affect plant preference in the wild. Several and young trees in gaps and small anthropogenic species show gregarious tendencies, from small secondary formations. Many of these species are larval hopper bands between 10 and 40 indivi- brightly coloured and brachypterous or apterous. duals (Leptysminae: Comops sp., Na.dia.cris sp.) Amedegnato and Descamps (1980) studied to numerous (up to 300), dense aggregations of composition, abundance and succession of forest black larvae of Chromacris icterus feeding on tox- grasshopper populations in primary and secon- ic Solanaceae (cf. Pfrommer 1990). With the ex- dary forests and their succession in indigenous ception of successional stages dominated by the old field communities at 6 Amazonian study ant-protected Cecropia tree, each successional sites (4 in NWA, one in southern Peru and one stage can be characterized by a typical communi- in Guyana). Abundance of canopy species varied ty of TFGs which often exceed the abundance of site-specific between 6 to 18 specimens per tree. primary forest species. In secondary formations, composition of species communities and abundance vary with succes- sion. It is minimal at 7 years, during dominance SOUTH-EAST ASIAN FOREST of the ant-inhabited Cecropia tree and reaches a GRASSHOPPERS maximum at 21 year old formations (Table 1). At Our knowledge of SEA grasshoppers is founded Mamepo site (NWA), abundance in 21 year for- on the early work of Ramme (1941) and the mation is 36 times higher than at a parcel of the extensive taxonomic studies of Willemse (1956, most populated primary forest (Colonia, Yubi- 1957). Many species descriptions are based on neto). An equally rieh gap fauna is known from single specimens. Type material was examined at Central America (cf. Rowell 1987; Braker 1991). the collection of F. Willemse, Eygelshoven; the Species composition and abundance of TFG aspect of a considerable number of species shows observed during my field studies on behavioural remarkable morphological convergences to the ecology in the Napo area of Amazonian Ecuador "dendrophilous" amazonian forms (Fig. 1). A was similar to the Mamepo site studied by Ame- further convergence can be observed between the degnato & Descamps. Between 1983 and 1989 I SEA genus Pemkia (Hemiacridinae) and Neotro- visited 21 logging operations (Riede 1990). pical genera like Hyleacris (Romaleidae), which Canopy grasshoppers were encountered at all are twig-mimicking, short winged forms with sites. Twenty per cent of medium-sized trees and excavated sterna, adapted to a cryptic life on all of epiphyte-rich emergents harboured grass- small branches ("dendrorhabdophiles"). The ex- hopper populations between 10 and 120 indivi- treme rarity of these forms in collections in- duals at various larval stages belonging to several dicates that these are accidental findings of a species. Sedentary species like Adrolampis colom- fauna limited to the tree tops. Females might des- biae or Trybliophorus sp. stayed at "their" trees cend for oviposition which could explain the for several days (Riede 1987). Observations of elevated percentage of females among unique undisturbed populations were made from simple type material. Systematically, most of these sup- wooden platforms at 4 sites, all of which har- posed canopy forms are subsumized under the boured small populations of canopy grasshop- artificial subfamily Catantopinae and urgently pers on neighbouring trees. need to be regrouped according to modern Gap-inhabiting species were observed in systematic criteria (cf. Table 1). In any case, they natural and anthropogenic secondary forma- are unrelated to the strictly Neotropical Roma-

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FIG. 1. Morphological convergences between canopy grasshoppers from SEA (a) and NWA (b). Both species are characterized by a vivid colouration, stout body form, protuberant eyes, contrasting colouration of hind femura and prolonged hind tarsae. a) Craneopsis olivaceus (Catantopinae), male, from Sibu (Sarawak), leg. F. Siegert (1986). This species was previously only known from a female specimen. The spine on the front femur is only present in the male and points to an interesting mating System, b) Helicopacris sp. (Bactrophorinae) from Limoncocha, Napo (Ecuador), leg. K. Riede. The red knees of hindlegs stand out from the greenish femura. leidae, to which many canopy forms belong (cf. found 466 Orthoptera among the 23874 ar- Amedegnato 1974). Several autochthonous ge- thropod specimens collected from 10 Bornean nera of ancient stock are limited to Borneo and trees by insecticide fogging. The majority were adjacent islands: the subfamily Borneacridinae is Ensifera, while Caelifera were represented by only represented by the monotypic genera Bomeacris 55 individuals, with a great proportion of and Moultonia (Kevan 1963); the description of Tetrigidae (47), 2 Eumastacidae and only 6 this subfamily was based on only 5 individuals acridid grasshopper specimens representing 3 and a single tegmen! A further example is the species (Table 1). In a sample of similar size eumastacoid genus Bomerianthus (Descamps (24 148 specimens) from Manaus, Erwin (1983) 1975). counted 1177 Orthoptera, but did not differen- Recent collecting expeditions to Sulawesi and tiate between Caelifera and Ensifera. Borneo did not add much to our knowledge of At the Poring study site, a canopy walkway the supposed canopy fauna, though canopy fogg- System of 300 m length provided access to dif- ing was done during both projects. Only two ferent strata of lowland mixed dipterocarp forest undescribed species were discovered besides con- at two sites 500 m apart. During a 6 weeks stay siderable collecting effort during Project Wallace, (April—May 1991), no canopy species could be Sulawesi (Butlin & Monk 1990). The same spotted (2 h control walks at different times of authors stress the low population densities of day, every two days). During two logging opera- forest grasshoppers. In Borneo, Stork (1991) tions, no canopy grasshoppers were found

214 within 6 man days of intensive search. Up to grasshoppers may partly be due to their low now, the only canopy specimen collected during abundance. As shown in Table l, there is a a logging Operation was found by F. Siegert at higher proportion of species belonging to grass- Sibu, Sarawak, in an epiphyte-rich mountain feeding subfamilies confined to savannah and forest (Fig. l a). open habitat. Bornean canopy grasshoppers do In small gaps (<500 sqm) and along forest exist, but their distribution is probably so punc- trails one regularily observes Traulia xan- tual that sampling efforts must be increased con- thostigma. This conspicuous species is also well siderably to get series of specimens comparable represented in museum collections. It resembles to collections of Neotropical species. Such local the South American Tetrataenia surinama which populations are extremely susceptible to extinc- inhabits forest gaps, edges and glades. Both tion, and in the light of current deforestation species have light-tipped antennae which facili- rates, it could be that single museum specimens tate optical communication. In contrast to the will remain our only testimony of their ex- gregarious South American species, populations istence. With respect to the SEA gap fauna, up to of T. xanthostigma consisted of few dispersed in- now there are no indications of such pronounced dividuals in each gap. In larger gaps (about l ha) faunal succession äs known from NWA. small colonies belonging to 4 species of the The data on SEA grasshopper abundance are genera Meltripata and Systella were observed. In still preliminary due to the limited number of one gap, a single population of 6 adult indivi- study sites and short observation periods. There duals of Meltripata sp. fed on a climber (Aristo- might be seasonal abundance fluctuations, in- lochiaceae) and stayed on this particular plant for cluding hyperannual cycles (mast years) or shifts 10 days, though this climber was abundant all to a nocturnal life style Despite these caveats, all over the gap. In other gaps, this species fed on observations indicate that forest grasshopper bamboo sprouts. All these gaps were inhabited abundance in SEA is lower than on any known by diurnal eneopterine crickets (Nisara sp.) in Amazonian site so that it seems justified to considerable densities (around 2 individuals/qm). speculate about possible reasons. These hypo- Dense populations of grass-feeding species theses are by no means mutually exclusive and like Oxya and Atractomorpha were observed in should also explain abundance differences larger, anthropogenic Clearings and rice fields, within one region. They could serve äs guide- but are not considered here äs they are not lines to find those refuges where SEA forest typical forest grasshoppers. grasshopper thrive. The extremely low abundance was confined to the Acridoidea, while other orthopteran Some hypotheses conceming differences in groups were represented well. Among the Caeli- TFG abundance: fera, several cryptic species of Tetrigoidea popu- In the following, four working hypotheses on lated mossy or rotten tree trunks. Discotettix potential constraints for the abundance of TFGs belzebuth inhabits humid logs were it feeds on are presented. The evidences are indirect and the soft rotting wood. Fern-eating Eumastacoi- by no means conclusive. They are thought äs a dea (Mnesides sp.) were observed regularly on framework for further investigations and more their food plants along trails and in small tree-fall rigorous tests. gaps. Among the Ensifera, a considerable num- ber of nocturnal Tettigonioidea and Grylloidea Hypothesis 1: Predation pressure Higher were caught at light and monitored acoustically predation pressure by insectivore birds, by sound recordings (Riede, in prep). mammmals, but especially ants could limit abundance of SEA grasshoppers. DISCUSSION Evidences: This is supported by a high proportion of Summing up, it can be said that the rarity of cryptic grasshoppers (Trigonopterygidae), acridoid grasshoppers in SEA is striking when which in addition to crypsis exhibit a high compared to Neotropical habitats, while abun- flight distance. An adverse effect of ants on dance of Tetrigoidea, Eumastacoidea and En- caeliferan populations is observed in SEA sifera does not show these remarkable differen- in the ant-rich heath forests, where Caeli- ces. Our incomplete knowledge of SEA canopy fera are practically absent. In successional

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stages, Macaranga trees in SEA and Cecropia Hypothesis 4: Plant palatability Low in the Neotropics are protected against her- grasshopper abundance could be a conse- bivores by symbiotic ants; for Macaranga, quence of a lower number of potential food Fiala (1989) has directly observed expulsion plants in SEA due to an elevated proportion of of grasshoppers by ants, for NWA, indirect toxic plants in SEA compared with NWA. evidence is provided by the low number of grasshoppers in the Cecnopza-dominated Evidences: successional stage (Amedegnato & Des- Compared with temperate regions, an camps 1980). elevated proportion of rain forest plants contains toxic substances äs a protection Hypothesis 2: Canopy architecture The structure against herbivores (Levin & York 1978). of NWA canopy is more favour-able for However, very few comparative data on grasshoppers due to a more stable micro-climate secondary compounds from different rain and a greater number of hiding places and forest regions exist, and the effect of these oviposition sites. substances on insects is debated. A study of Evidences: Waterman (1983) compares total phenolics, In comparison to NWA, SEA canopy is Condensed tannin and fibre Contents from characterized by a higher number of five rain forests and reveals an increased emergents and a lower number of epiphytes fibre content at the SEA dipterocarp forest (Whitmore 1984). Microclimatic fluctua- (Sepilok, Sabah) compared with the tion above the lower boundary of the Neotropical study site (Costa Rica). Higher canopy ("inversion zone": Halle et al. 1978) fibre content implies relative N-deficiency are considerable, especially at the Poring and would especially affect the growth of walkway site due to a rugged terrain and ex- first instar grasshopper larvae (White 1984), tremely high trees. Crown "shyness" is an so that low grasshopper abundance could additional feature supporting the more lof- be explained by lower nitrogen availability ty aspect of Bornean forest. It gives ample in Bornean plants. This Interpretation room for the rieh flying fauna of otherwise would explain the greater abundance of earthbound like frogs and lizards. crickets, Tetrigoidea and Eumastacoidea: In comparison, NWA canopy is a mono- adults of the abundant gap-inhabiting layer of low height between 25—30 m with cricket Nisara feed on plants, while their heavy epiphyte load and rieh humus accu- larvae could overcome the critical larval mulations providing shelter and Substrate stage by omnivory and switch to foliovory for oviposition. Note that most of the SEA museum material of supposed canopy later during ontogeny. Tetrigoidea and grasshoppers are females which might have Eumastacoidea feed on "primitive" plants descended to oviposit for want of canopy like mosses, ferns, algae or even dead wood humus. and it has been hypothesized by Blackith (1987) that their strategy of transferring Hypothesis 3: Plant diversity Higher plant huge spermatophores äs nuptial gifts is an diversity in SEA hampers discovery and adaptation to overcome the low nutritional colonization of potential food plants by value of these foods. The conservancy of specialized herbivores of low mobility or host the association between Tetrigoidea/Euma- finding capacity. stacoidea and lower plants indicates that Evidences: host plant switch to higher plants is Especially the Kinabalu area, is famous for obstructed by their toxicity. its elevated floristic diversity (Stein 1978), Monk (1987) observed occasional which could exceed the host finding capaci- feeding of SEA grasshoppers on "unusual" ty and mobility of short-winged grasshop- food items such äs fungi and animal pers. To investigate this hypothesis, data on fragments. Together with the feeding on the degree of feeding specialization of senescent leaves, these strategies could be in- canopy grasshoppers are necessary. terpreted äs adaptations to N-deficiency.

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CONCLUSIONS Blackith, R. E. 1987. Primitive Orthoptera and primitive plants. Pp. 124—126 in Baccetti, B. M. The study of coevolution between insects and (ed.). Evolutionary Biology of Orthopteroid In- plants is most advanced in the highly specialized sects. Chichester. butterflies and Chrysomelidae which are ex- amples par excellence of the result from the arm's Braker, E. 1991. Natural history of a neotropical gap- race between plants and insects (cf. Farrel et al. inhabiting grasshopper. Biotropica 23: 41—50. 1992). Grasshoppers do not show such high Butlin, R. K., & K. A. Monk 1990. Catantopine degrees of specialization but nevertheless are in- grasshoppers of Sulawesi. Pp. 89—93 in Knight, W. J., &. J. D. Holloway (eds.). Insects and the rain timately related to host plant properties which forests of South East Asia (Wallacea). London. may include a variety of parameters like nutri- tional value, toxicity, abundance and architec- Cherrett, J. M. 1986. History of the leaf-cutting ant tural properties. They feed principally on leaves Problem. Pp. 10-17 in Lofgren, C. S., & R. K. throughout their life and show no major shift in Vander Meer (eds.). Fire ants and leaf-cutting ants: biology and management. Boulder. feeding strategy in the course of larval develop- ment. Endosymbionts are not known from Descamps, M. 1970. Geographical regions and tax- grasshoppers which makes them especially onomic groups of Acridomorpha in need of study. susceptible to food plant quality. These dif- Proc. Int. Study Conf. Current and Future Pro- blems of Acridology. London. ferences to other phyllophagous insects provide an additional scenario for the analysis of in- Descamps, M. 1975. Revision du genre Erianthus sect/plant relations. STÄL, 1875 [Orth. Eumastacoidea, Erianthinae]. Ann. Soc. ent. Fr. (N. S.) 11: 91-136. ACKNOWLEDGEMENTS Descamps, M. 1976. Le peuplement acridien d'un perimetre d'Amazonie colombienne. Annls. Soc. I want to thank Sabah Parks for the generous ent. Fr. (N. S.) 12: 291—318. support of this study by providing housing, Elton, C. S. 1973. The structure of invertebrate popula- transportation and assistance by park personnel. tions inside Neotropical rain forest. J. Anim. Ecol. Especially, I want to thank Thomas Yussop for 42: 55-104. his permanent and enthusiastic help in the field, Erwin, T. L. 1983. Beetles and other insects of tropical and park ecologist Jamili Nais for helpful discus- forest canopies at Manaus, Brazil, sampled by insec- sion and logistical support. Fieldwork in SEA is ticidal fogging. Pp. 59—76 in Sutton, S. L., Whit- supported by the DFG Schwerpunkt (Mechanis- more, T. C., & A. C. Chadwick (eds.). Tropical men der Aufrechterhaltung tropischer Diver- rain forest ecology and management. Oxford. sität). Fieldwork in Ecuador was generously sup- Farrell, B. D., Mitter, C., & Futuyma, D. J. 1992. ported by the Max-Planck-Institute Seewiesen Diversifikation at the insect-plant interface. Bio- and facilitated by the hospitality of the Secoya Science 42: 34—42. indigenous Community (San Pablo, Ecuador). I Fiala, B., Maschwitz, U, Pong, T. Y., & A. J. Heibig thank Dr. C. Amedegnato, Museum d'Histoire 1989. Studies of a South East Asian ant-plant Naturelle of Paris, for stimulating discussions association: protection of Macaranga trees by and Dr. F. Willemse for his introduction to SEA Crematogaster bomeensis. Oecologia 79: 463—470. grasshopper systematics. I am indebted to Dr. F. Fittkau, E.-J. 1985. Ökologische und faunenhistorische Siegert, Munich, for having provided his preci- Zoogeographie der tropischen Regenwälder — Ver- ous Bornean Orthoptera collection. such eines Vergleichs. Verh. Dtsch. Zool. Ges. 78: 137—146. REFERENCES Hall4 F., Oldeman, R. A., & P. B. Tomlinson 1978. Amedegnato, C. 1974. Les genres d'Acridiens Tropical trees and forests. Berlin. neotropicaux leur classification par familles, sous- Kevan, K. D. 1963. A note on the Borneacridinae familles et tribus. Acrida 3: 193—204. (Orth. Acridoidea). Eos 39: 279-283. Amedegnato, C., & M. Descamps 1980. Etüde com- Levin, D. A., & B. M. York 1978. The toxicity of plant parative des quelques peuplements acridiens de la alkaloids: an ecogeographic perspective. Biochemi- foret neotropicale Acrida 9: 171—216. cal systematics and ecology 6: 61—76. Amedegnato, C., & M. Descamps 1982. Dispersal Monk, K. A. 1987. A comparison of the diets of some centers of the Amazonian acridids. Acta rainforest grasshopppers (Orthoptera: Acrididae) in Amazonica 12: 155—165. Malaysia. Malay. Nat. J. 41: 383-391.

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Pfrommer, A. 1990. Freilandbeobachtungen zur Etho- Stein, N. 1978. Coniferen im westlichen Malayischen logie und Ökologie der neotropischen Feldheu- Archipel. The Hague, Biogeographica. schrecken Chromacris icterus (Romaleinae, Acridoi- dea) und Comops frenatum frenatum (Leptysminae, Stork, N. E. 1988. Insect diversity: facts, fiction and Acridoidea) unter besonderer Berücksichtigung speculation. Biol. J. Linn. Soc. 35: 321—337. ihrer Larvenverbände Universität Hamburg, Di- Stork, N. E. 1991. The composition of the plomarbeit. fauna of bornean lowland rain forest trees. J. Trop. Ramme, W. 1941. Beiträge zur Kenntnis der Acrididen- Ecol. 7: 161—180. Fauna des indomalayischen und benachbarter Ge- biete (Orth.). Mitt. zool. Mus. Berl. 25: 1—243. Wallace, A. R. 1869. The Malay archipelago. Scotland, Tynron press 1989. Riede, K. 1987. A comparative study of mating beha- viour in some neotropical grasshoppers (Acridoi- Waterman, P. G. 1983. Distribution of secondary meta- dea). Ethology 76, 265—296. bolites in rain forest plant: toward an understan- Riede, K. 1990. Orthopterological studies in eastern ding of cause and effect. Pp. 167—180 in Sutton, Ecuador (Part I). Metaleptea 12: 4—5. S. L., Whitmore, T. C., & A. C. Chadwick (eds.). Riede, K., Kämper, G., & I. Höfler 1990. Tympana, au- Tropical rain forest ecology and management. Ox- ditory thresholds and projection areas of tympanal ford. nerves in singing and silent grasshoppers (Insecta, White, T. C. 1984. The abundance of invertebrate her- Acridoidea). Zoomorphology 109: 223—230. bivores in relation to the availability of nitrogen in Roberts, H. R. 1973. Arboreal Orthoptera in the rain stressed food plants. Oecologia 63: 90—105. forest of Costa Rica collected with insecticide: A report on the grasshoppers (Acrididae), including Whitmore, T. C. 1984. Tropical rain forests of the Far new species. Proc. Acad. Nat. Sei. Philad. 125: East. Oxford. 49-66. Willemse, C. 1956. Synopsis of the Acridoidea of the Rowell, C. H. 1987. The biogeography of Costa Rican Indo-Malayan and adjacent regions. Natuurhisto- acridid grasshoppers, in relation to their putative risch Genootschap in Limburg 8: l—225. phylogenetic origins and ecology. Pp. 470—482 in Baccetti, B. M. (ed.). Evolutionary Biology of Ort- Willemse, C. 1957. Synopsis of the Acridoidea of the hopteroid Insects. Chichester. Indo-Malayen and adjacent regions Part II. Natuur- Schmidt, G. H. 1987. Adaptation of Saltatoria to vari- historisch Genootschap in Limburg 10: 227—500. ous climatic factors with regard to their survival in Wint, G. R. 1983. Leaf damage in tropical rain forest different geographical regions. Pp. 550—565 in Bac- canopies. Pp. 229—240 in Sutton, S. L., Whitmore, cetti, B. M. (ed.). Evolutionary Biology of Orthop- T. C., & A. C. Chadwick (eds.). Tropical rain forest teroid Insects. Chichester. ecology and management. Oxford.

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