The impact of a small, alien invertebrate on a sub-Antarctic terrestrial ecosystem: Limnophyes minimus (Diptera, Chironomidae) at Marion Island

Density and biomass of the larvae of a small, alien chironomid midge, Limnophyes minimus, whose parthenogenetic adult females do not feed, were quantified for ten major lowland plant communities at sub-Antarctic Marion Island (46°52′S 37°51′E) and compared with the density and biomass of indigenous macro-invertebrates in the same communities. An estimate of litter consumption by larvae of this midge was also made. L. minimus reached high densities in most of the plant communities sampled, with the highest density being recorded in the Cotula plumosa biotically influenced community (annual mean of 4,365 individuals m⁻²) and the lowest in the Crassula moschata salt spray community (annual mean of 41 individuals m⁻²). Estimates of litter ingestion indicated that L. minimus larvae are capable of consuming between 0.07 and 8.54 g_{(dry mass)} m⁻² per year, depending on the community. In some communities this litter consumption amounted to an order of magnitude more than that consumed by Pringleophaga marioni (Lepidoptera, Tineidae). Although the larvae of this moth species are thought to represent the bottleneck to nutrient recycling on the island, this study showed that midge larvae may also contribute substantially to this process. As a consequence, the considerable changes that have been predicted to occur in Marion Island's terrestrial ecosystem as a consequence of enhanced predation by mice on P. marioni larvae may be retarded or obscured by the contribution of the midge larvae to nutrient cycling. Hence, it is suggested that greater attention be given to the small and inconspicuous elements of the alien sub-Antarctic faunas because such species may have profound consequences for ecosystem functioning on these islands. Received: 17 November 1997 / Accepted: 23 February 1998     

Life cycle of a giant carnivorous caddisfly, <Emphasis Type="Italic">Himalopsyche japonica</Emphasis> (Morton) (Trichoptera: Rhyacophilidae), in the mountain streams of Nagano,Central Japan

 The life cycle of a giant carnivorous caddisfly, Himalopsyche japonica (Morton), was studied in two mountain streams in Nagano Prefecture, Central Japan. Field surveys and rearing experiments in the laboratory were conducted from October 1997 to September 2001. The life cycle of H. japonica was estimated to be a complex univoltine cycle that partly includes bivoltine populations. The adults had a long flight period, from April to September, with three distinct peaks of emergence. First to third instar larvae were collected from June to February, and the last (fifth) instar larvae and pupae appeared throughout the year. In autumn, the larvae belonging to all instars were found, and younger ones overwintered in the fourth instar stage and others in the fifth instar stage. On the other hand, fifth instar larvae and pupae ceased developing in autumn even though the water temperature was higher than the developmental zero temperature. The overwintered pupae emerged as adults in April, and the overwintered fifth instar larvae pupated in May and emerged in June. The larvae which overwintered in the fourth instar stage probably emerged after June. Received: March 19, 2002 / Accepted: January 10, 2003 Present address: United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan Tel. +81-265-77-1401; Fax +81-265-74-7496 e-mail: himalo@f8.dion.ne.jp Acknowledgments The author thanks Prof. T. Yoshida, Prof. H. Nakamura, and Associate professor K. Soma, Shinshu University; Mr. T. Nozaki, Kanagawa Environmental Research Center; and Mr. N. Kubota, Environmental Assessment Center in Matsumoto laboratory for their advice and help in accomplishing this research. The author is also grateful to Prof. K. Tanida, Osaka Prefecture University; Dr. T. Ito, Hokkaido Fish Hatchery; Mr. K. Okazaki, Kutchan City Museum; and Mrs. Y. Isobe, Nara Women's University, for suggesting references. Miss. T. Ishiyama, Mr. H. Kojima, Mr. M. Yagyu, and the students of the Forest Animals Laboratory in Shinshu University kindly provided field samples. Correspondence to:T. Tsuruishi     

Surplus Killing by Predatory Larvae of <Emphasis Type="Italic">Corethrella appendiculata</Emphasis>: Prepupal Timing and Site-Specific Attack on Mosquito Prey

Surplus or ‘wasteful’ killing of uneaten prey has been documented in the fourth larval instar of various species of the mosquito genus Toxorhynchites that occur in treeholes and other phytotelmata. Here we document surplus killing by the predatory midge Corethrella appendiculata, which in Florida cohabits treeholes and artificial containers with larvae of Toxorhynchites rutilus. Provided with a surfeit of larval mosquito prey, surplus killing was observed only in the fourth instar of C. appendiculata, peaking in intensity in the final 24 h prior to pupation, as observed for Toxorhynchites spp. Attack sites identified from videotaped encounters with mosquito prey were divided among head, thorax, abdomen, and siphon. Consumed mosquito larvae (n = 70) were attacked primarily on the head (46%) or siphon (34%), but surplus-killed prey (n = 30) were attacked predominantly on the thorax (83%). Despite its independent evolution among different insect species in aquatic container habitats, the functional significance of prepupal surplus killing remains unclear.     

From competent larva to exotrophic juvenile: a morphofunctional study of the perimetamorphic period of Paracentrotus lividus (Echinodermata, Echinoida)

 The perimetamorphic period in Paracentrotus lividus lasts for 8–12 days. It starts from the acquisition of larval competence, includes the change in form (metamorphosis) and the endotrophic postlarval life, and stops with the appearance of the exotrophic juvenile. All major postlarval appendages already occur in competent larvae being either grouped into the echinoid rudiment (terminal plates, early spines and primary podia) or scattered within the larval integument (genital plates and sessile pedicellariae). Competent larvae show particular behaviour which brings them close to the substratum. The latter is tested by primary podia protruding through the vestibular aperture of the larva. Primary podia are sensory–secretory appendages that are deprived ampullae. They are able to adhere to the substratum in order to allow evagination of the echinoid rudiment (i.e. metamorphosis) and substatum adhesion of the postlarva. Particular spines are borne by the postlarva; these are multifid non-mobile appendages forming a kind of protective armour. Like those of the larva, all characteristic structures of the postlarva (primary podia, multified spines and sessile pedicellariae) are transitory and regress either at the end of postlarval life (primary podia) or during early juvenile life (multifid spines and sessile pedicellariae). Other appendages that develop during postlarval life (i.e. podia with ampulla, point-tipped spines and sphaeridiae) are similar to those borne by the adults and become functional when the individual enters its juvenile life. Thus, the perimetamorphic period appears to be a fully fledged period in the life-cycle of P. lividus, and presumably in the life-cycle of any other sea-urchin species. Accepted: 7 October 1997     

Larval and juvenile development of <Emphasis Type="Italic">Lestidiops sphyraenopsis</Emphasis> Hubbs, 1916 (Aulopiformes: Paralepididae) in the western North Pacific,with a reexamination of the holotype of <Emphasis Type="Italic">Stemonosudis molesta</Emphasis> (Marshall, 1955)

The early life stages of Lestidiops sphyraenopsis (Paralepididae) are described on the basis of 14 specimens [7.8 mm in notochord length (NL)–88.6 mm in standard length (SL)] collected from the western North Pacific, and the holotype of Stemonosudis molesta is reexamined. Larval L. sphyraenopsis occurred in the Kuroshio waters, and juveniles were taken in the Kuroshio–Oyashio transition waters. Diagnostic characters of larval and juvenile L. sphyraenopsis are 96–101 myomeres; 27–31 anal fin rays; 4–9 peritoneal pigment sections in larvae (7.8 mm NL–27.3 mm SL); dorsal and anal pigment patches present; and anus located anterior to a vertical through dorsal fin origin. Stemonosudis molesta, known only from the holotype from the South Pacific, is similar to immature specimens of L. sphyraenopsis, but can be clearly distinguished from the latter by having higher vertebral counts (105 vs. 96–101) and by morphometric and pigment differences. Consequently, S. molesta is a valid species, and the distribution of L. sphyraenopsis is restricted to the North Pacific.     

Reproductive and sexual characteristics in five Lethrinus species in waters off the Ryukyu Islands

Gonads of five lethrinids, viz., Lethrinus harak, L. miniatus, L. obsoletus, L. ornatus, and L. sp. 2, were collected monthly in waters off the Ryukyu Islands and observed histologically to reveal their spawning periods and size at sexual maturation and sexual transition. The spawning period was from April to November for L. harak, from April to July for L. miniatus, from April to October for L. obsoletus, from May to November for L. ornatus, and from April to October for L. sp. 2. Sexual patterns in the five species were determined by fork length at both sexual maturation and sexual transition. The body size (fork length, FL) and sex ratio (% of female) at 90% maturity in L. harak were 21.1 cm FL and 90%, respectively; those of L. miniatus were 42.2 cm FL and 80%; 25.7 cm FL and 60% for L. obsoletus; about 20 cm FL and 90% for L. ornatus; and about 26 cm FL and 90% for L. sp. 2. Because the sex ratios decreased to 0% at the maximum size classes in L. miniatus, L. ornatus, and L. sp. 2, the sexual patterns in these species were considered to be protogynous hermaphrodite. Although the sex ratio (% of female) once decreased to about 30% at 28 cm FL, rapid increase occurred in the larger size class in L. harak. However, the increase did not result from sexual transition. Hence, the sexual pattern of L. harak was considered to be protogynous hermaphrodite. Because the sex ratio (% of female) at body sizes larger than 23 cm FL was stable at about 60% in L. obsoletus, the sexual pattern was determined to be one of juvenile hermaphrodites.     

Kelp degradation by Paractora trichosterna (Thomson) (Diptera: Helcomyzidae) at sub-Antarctic South Georgia

 The Diptera are one of the dominant insect consumer groups on sub-Antarctic islands and are thought to contribute significantly to terrestrial ecological processes at many of these islands. The life-cycle of Paractora trichosterna and its contribution to kelp degradation at Husvik Harbour, South Georgia were therefore investigated in the laboratory and in two artificial wrack beds in the field. Duration of the larval stage was approximately 2 months at 10°C, during which time larvae attained a maximum individual mass of ca. 90 mg. Larvae had a relative consumption rate of 0.734 mg dry mass kelp mg dry mass larva^-1 day^-1. Based on this rate and information on larval densities of P. trichosterna, and a smaller species, Antrops truncipennis, kelp consumption was estimated to be 714–870 g dry mass kelp m^-2 over the 7-week study period. During this time, kelp dry biomass declined to 30% of its original value, both in a bed protected from trampling by vertebrates and in an exposed one. P. trichosterna was directly responsible for 12% of this loss in the protected bed and 20% in the exposed one. A. truncipennis was responsible for an additional 3% loss in the exposed bed and 8% in the protected one. These fly species therefore contributed significantly to kelp degradation. Differences in biomass of the larvae and adults of the two species between the beds suggested that P. trichosterna prefers more exposed wrack than does A. truncipennis. Received: 27 March 1995/Accepted: 4 July 1995     

Thermal tolerance and acclimation response of larvae of the sub-Antarctic beetle Hydromedion sparsutum (Coleoptera: Perimylopidae)

Hydromedion sparsutum is a locally abundant herbivorous beetle on the sub-Antarctic island of South Georgia, often living in close association with the tussock grass Parodiochloa flabellata. Over a 4-day period in mid-summer when the air temperature varied from 0 to 20°C, the temperature in the leaf litter 5–10 cm deep at the base of tussock plants (the microhabitat of H. sparsutum) was consistently within the range of 5–7.5°C. Experiments were carried out to assess the ability of H. sparsutum larvae collected from this thermally stable environment to acclimate when maintained at lower (0°C) and higher (15°C) temperatures. The mean supercooling points (freezing temperature) of larvae collected in January and acclimated at 0°C for 3 and 6 weeks and 15°C for 3 weeks were all within the range of −2.6 to −4.6°C. Larvae in all treatment groups were freeze tolerant. Acclimation at 0°C significantly increased survival in a 15-min exposure at −8°C (from 27 to 96%) and −10°C (from 0 to 63%) compared with the field-fresh and 15°C-treated larvae. Similarly, survival of 0°C-acclimated larvae in a 72-h exposure at −6°C increased from 20 to 83%. Extending the acclimation period at 0°C to 6 weeks did not produce any further increase in cold tolerance. The concentrations of glucose and trehalose in larval body fluids increased significantly with low temperature acclimation. Larvae maintained at 15°C for 3 weeks (none survived for 6 weeks) were less able to survive 1-h exposures between 30 and 35°C than the 0°C-treated samples. Whilst vegetation and snow cover are an effective buffer against low winter temperatures in many polar insects, the inability of H. sparsutum larvae to acclimate or survive at 15°C suggests that protection against high summer temperatures is equally important for this species. Accepted: 2 August 1999     

The eggs and larvae of the giant mudskipper, <Emphasis Type="Italic">Periophthalmodon schlosseri</Emphasis>, collected from a mudflat in Penang,Malaysia

 Eggs of the giant mudskipper, Periophthalmodon schlosseri were collected from a burrow in Penang, Malaysia, in November 1998, and hatched larvae were reared in the laboratory. The eggs were demersal with adhesive filaments and elliptical in shape (0.83–1.43 mm in long-axis diameter). Newly hatched larvae (2.1–2.6 mm in notochord length) possessed a yolk sac. The number of myomeres was 10 + 17 = 27. The mouth and anus were already opened. The larvae started feeding one day after hatching and completely absorbed the yolk by the third day at a water temperature of 24.5–28.0°C. Received: April 9, 2002 / Revised: October 25, 2002 / Accepted: December 10, 2002     

Microphytoplankton assemblages in the waters surrounding South Georgia, Antarctica during austral summer 1994

The composition and distribution of microphytoplankton assemblages in the vicinity of South Georgia were examined during a krill survey conducted during voyage 119 the RV Africana in austral summer (January/February) 1994. Microphytoplankton distribution was studied at 83 stations along a zig-zag transect in the waters surrounding South Georgia. Oceanographic and zooplankton data suggest that conditions were anomalous during the investigation, in that sub-Antarctic surface waters had probably been advected southwards and were present around the island. The two most widely distributed species were Corethron criophilum and Eucampia antarctica, which were recorded at all stations sampled. Also well-represented amongst the microphytoplankton assemblages were temperate, neritic species such as Chaetoceros atlanticus, Proboscia alata and Odontella weissflogii. This can probably be related to the intrusion of sub-Antarctic surface waters unusually far south. Cluster and ordination analysis identified three distinct groupings of stations in the waters surrounding the islands. These were found to the east, west and north of the islands. The diatom groupings identified during this investigation broadly correspond to three water masses previously described in the vicinity of South Georgia. Despite the anomalous hydrographical conditions that existed during the investigation, the differences in phytoplankton were negligible when compared to normal years. Small mesoscale features are, however, important in imposing biogeographic patterns on microphytoplankton. Received: 21 February 1996 / Accepted: 3 November 1996     

Recruitment of the amphidromous goby <Emphasis Type="Italic">Sicyopterus japonicus</Emphasis> to the estuary of the Ota River,Wakayama, Japan

Ecological aspects of recruitment in the amphidromous goby, Sicyopterus japonicus, were studied from larval collections made with a set net in the estuary of the Ota River, Wakayama, Japan. The abundance patterns of the 12,766 larvae collected from 18 April to 26 August 2006 showed several peaks during the recruitment season. Their body sizes at recruitment ranged from 23.5 to 30.0 mm standard length (mean ± SD, 26.3 ± 1.1 mm), 0.11 to 0.49 g body weight (0.22 ± 0.05 g), and 8 to 20 condition factor (11 ± 2). The standard length of the goby larvae tended to decrease with the season, while their body weight slightly increased and resulted in an increase in condition factor. The recruitment of larvae occurred mainly during the daytime. Otolith growth increment analysis of 30 larvae collected by a square lift net on 30 April 2005 revealed that the oceanic larval duration after downstream migration ranged from 173 to 253 days (208 ± 22) after hatching. A limited time of recruitment in early summer and a considerably long duration of oceanic life (about a half year) appeared to be unique characteristics of this Sicyopterus species that lives in a temperate region in comparison to other tropical species of the genus Sicyopterus that all have year-round recruitment.     

The biology of Bothrometopus elongatus (Coleoptera, Curculionidae) in a mid-altitude fellfield on sub-Antarctic Marion Island

Bothrometopus elongatus is one of four Ectemnorhinus-group species restricted to the epilithic biotope on the Prince Edward Islands. Here we examine the biology of this species over a full year at Kerguelen Rise, a mid-altitude fellfield site on Marion Island. B. elongatus adults eclose from April onwards, reaching maximum densities (ca. 17 individuals m⁻²) in September. Females mature approximately three eggs at a time and these commence hatching in July. Larval eclosion reaches a peak in November, during which time larval densities are also highest (ca. 153 individuals m⁻²). The larvae develop through six instars, which is within the range found for other Ectemnorhinus-group species. The high densities of B. elongatus in fellfield habitats, and its single, virtually discrete annual generation, make this species unusual among insects indigenous to the sub-Antarctic. The latter generally have low densities compared to other micro-arthropods, prolonged life-cycles, and flexible life-histories. We suggest that the diversity of life-histories found amongst the indigenous insects at Marion Island presents considerable potential for testing environmental effects on insect life-histories. An overview of sub-Antarctic insect life-history data suggests that the indigenous species, with generally prolonged life-cycles, are at a disadvantage relative to introduced species that have more rapid cycles and often complete several generations per year. This is reason for concern given rapid climate change at these islands. Accepted: 14 November 1999     

Foraging in a pathogen reservoir can lead to local host population extinction: a case study of a Lepidoptera-virus interaction

In 1990, natural infestations of the polyphagous vapourer moth, Orgyia antiqua (Lepidoptera: Lymantriidae) in lodgepole pine plantations in northern Scotland, were studied to ascertain the role of host foraging behaviour on the prevalence of nucleopolyhedrovirus (NPV; Baculoviridae) infection in the population. Aerial dispersal of early instar larvae (L1–L3) from the tree canopy onto heather foliage at the forest understorey, with subsequent relocation back onto the tree as late-instar larvae (L4–L6) appeared to play a significant role in the development of a widespread virus epizootic in which approximately 80% of L4–L6 individuals succumbed to disease. Bioassays of foliage 1 year later showed that the distribution of NPV followed a pronounced vertical gradient through the forest canopy culminating in high concentrations of virus in the forest understorey. Experimental systems comprising potted pine trees positioned above heather bases showed that NPV infections could be acquired by early stage larvae following dispersal from the tree and feeding on the undercanopy vegetation, then translocated to the tree component for secondary transmission to susceptible tree-feeding individuals. Behavioural studies indicated that the tendency for first-, second- and third-instar larvae to disperse to the understorey was probably not influenced by larval density on the tree but was strongly dependent on larval instar. In contrast, the tendency for larvae to relocate from the understorey heather to the tree was affected by both larval density and larval instar, suggesting that both these factors may significantly affect virus acquisition, translocation and transmission in the host population. In the present study, the heather understorey appeared to act as a pathogen reservoir in which virus could persist between host generations. Spatial heterogeneity in virus distribution combined with host foraging behaviour (dispersal and feeding) resulted in the pathogen playing a major role in host population dynamics over an extended time period (3 years). The reservoir theory is supported by the observation that similar dynamics were not observed in O. antiqua populations at neighbouring sites which lacked understorey food plants. Received: 8 June 1998 / Accepted: 5 October 1998     

The population dynamics of an introduced tree, Sesbania punicea, in South Africa, in response to long-term damage caused by different combinations of three species of biological control agents

This paper contributes to the relatively sparse literature on the effects of insect herbivory on the population dynamics of plants and is probably unique in that it reports the long-term effects of combinations of three insect herbivore species on the population densities of a moderately long-lived tree species. The tree is Sesbania punicea, a leguminous perennial from South America that has been the target of a biological control programme in South Africa for almost 20 years. Sixteen infestations of the weed have been monitored for periods of up to 10 years to determine changes in the density of the mature, reproductive plants under the influence of different combinations of three biological control agents (i.e. with one, two or three of the agent species present in the weed infestation). The three biological control agents, all weevil species, include Trichapion lativentre, which primarily destroys the flower-buds, Rhyssomatus marginatus, which destroys the developing seeds, and Neodiplogrammus quadrivittatus, whose larvae bore into the trunk and stems of the plants. While T. lativentre occurs throughout the range of the weed in South Africa, the other two species are less mobile, more recent introductions and are largely confined to the vicinity of selected release sites. There has been a significant decline in the density of mature S. punicea in areas where two or more of the agents are established. The decline of the weed has been most evident where N. quadrivittatus is active and particularly so where both of the other two weevil species are also present. Received: 2 April 1997 / Accepted: 30 November 1997     

Larval development of Pseudorhombus oculocirris and P. arsius (Pleuronectiformes, Paralichthyidae) from off southern Japan

 Larvae of two paralichthyids, Pseudorhombus oculocirris and P. arsius, are described and illustrated from specimens collected off Tosa Bay, southern Japan. Peudorhombus oculocirris larvae (5 specimens, 4.5–7.8 mm BL) are characteristic in having 6 or 7 elongated anterior dorsal fin rays and poorly developed head spines and melanophores on the tail. Pseudorhombus arsius larvae (3 specimens, 5.3–8.4 mm BL) are distinctive in having 11 or 12 elongated anterior dorsal fin rays and well-developed head spines, including a row of spines on the sphenotic. Received: June 28, 2001 / Revised: November 2, 2001 / Accepted: November 22, 2001     

Morphology and development of <Emphasis Type="Italic">Pteromalus cerealellae</Emphasis> (Ashmead) (Hymenoptera: Pteromalidae) on <Emphasis Type="Italic">Callosobruchus maculatus</Emphasis> (F.) (Coleoptera: Chrysomelidae)

Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae) is an ectoparasitoid of several stored-product insect pests. Very little information has been published on its biology and development in host larvae, which typically are concealed within seeds. We documented the development of P. cerealellae within fourth instar larvae of its concealed host, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) infesting cowpea seeds. The preimaginal life stages of the parasitoid were characterized for the first time using morphological structures revealed by microscopic techniques including scanning electron microscopy. Pteromalus cerealellae produces hymenopteriform eggs and larvae. Eggs hatch into 13-segmented first instar larvae with peripneustic condition of spiracles. The larvae have simple, tusk-like mandibles, whereas the mandibles of the pupae and the adults are of the conventional toothed types. Using statistical analyses of the sizes of the larval mandibles and head capsules in conjunction with reliable characters such as the number of exuviae on the body of parasitoid larvae, cuticular folding, and excretion of the meconium, we recorded four larval instars for P. cerealellae. The data showed significant positive correlations between larval mandible lengths and widths of larval head capsules, as well as between mandible lengths and larval instars, suggesting that mandible length is a good predictor of the number of instars in P. cerealellae. Developmental time from egg to adult emergence was ∼12 d for females and ∼11 days for males at 30 ± 1°C, 70 ± 5% r.h. and 12L:12D photoperiod.     

Development and functional response of Coelophora inaequalis (Coleoptera: Coccinellidae) feeding on brown citrus aphid, Toxoptera citricida (Homoptera: Aphididae)

1 Development and survivorship of Coelophora inaequalis (F.) were evaluated in the laboratory on the brown citrus aphid, Toxoptera citricida (Kirkaldy) at 20 and 25 °C. Coelophora inaequalis could complete its life cycle feeding on T. citricida at these two temperatures. The developmental period from egg to adult was significantly longer at 20 °C (24.7 d) than at 25 °C (15.9 d). The survivorship of combined immature stages were higher at 25 °C (39.2%) than at 20 °C (34.3%). 2 The effects of prey densities (4–64 aphids per leaf disk) on the functional responses of C. inaequalis fourth‐instar larvae and female adults were investigated using grapefruit leaf disks over a 24‐h period at 25 °C and a photoperiod of LD 14 : 10 h. Logistic regression analyses indicated that fourth‐instar larvae and adults exhibited a type II functional response to aphid density. Fourth‐instar larvae had a higher search rate (0.1305) than C. inaequalis female adults (0.0989). The handling time of fourth‐instar larvae (30.4 min) was significantly longer than that of female adults (5.8 min). Collectively, C. inaequalis appears to be a promising biological control agent of T. citricida in the citrus groves.     

Dietary items of predacious aquatic bugs (Nepoidea: Heteroptera) in Japanese wetlands

Some species of predatory aquatic bugs (Nepoidea, including Belostomatidae and Nepidae) are designated as threatened-vulnerable species in the Red Data Book of Japan and are regarded as effective predators of freshwater snails and mosquito larvae. To reveal the feeding habits of Nepoidea, we investigated their dietary items in wetlands and obtained data from the published literature. Lethocerus deyrolli (Vuillefroy) preys mainly upon frogs, and the major diet of the nymphs is tadpoles. Laccotrephes japonensis (Scott) adults prey mainly upon tadpoles. Lethocerus deyrolli nymphs and L. japonensis adults compete against each other as same-guild members because they are sympatric in wetlands. Both nymphs and adults of Appasus japonicus (Vuillefroy) feed on snails, and L. japonensis nymphs feed on aquatic insects, including mosquito larvae (39.3% of aquatic insects). These species are effective predators of medically important pests such as snails, and mosquito larvae.