Seventh Instars Research Articles

The ontogeny of appendages and carapace of Neonesidea schulzi (Ostracoda: Bairdiidae) from the Red Sea coast, Egypt

The ostracod genus Neonesidea is broadly distributed in shallow marine waters. The ontogeny of the N. schulzi (Bairdiidae) is described in detail by studying the development of the appendages and variations in carapace form, size and structure. Neonesidea schulzi has eight post-embryonic instars, and a gap in its ontogenetic development during instar A-6, where no new Anlage is added. The Anlagen of the copulatory organs and the forked terminal claw of second antenna appear in the seventh (A-1) instar, and the first thoracic legs of podocopid ostracods are shown to descend from the thoracic region. For the first time in ostracods, observations of moulting from sixth and seventh instars are presented.

Baseline Responses ofAlphitobius diaperinus(Coleoptera: Tenebrionidae) to Insect Growth Regulators

J. Agric. Urban Entomol. 29: 35-54 (2013) ABSTRACT The cancellation of most organophosphate and carbamate insecticides, and the emerging resistance to currently available insecticides for managing the lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), necessitate efficacy studies on other classes of insecticidal compounds. Baseline dose-response bioassays were conducted with three different types of insect growth regulators (IGRs), fenoxycarb, diflubenzuron, and 20-hydroxyecdysone (20E) on first and seventh instars, two day-old pupae, and one-week-old adult beetles. Insects were exposed to a range of concentrations through topical application, by residual contact with treated wood shavings, and through feeding on treated chicken feed diet. Insects were observed at 10-day intervals to estimate mortality, pupation, and abnormal growth for each treatment. The mean number of days to pupation increased and pupation was delayed in fenoxycarb-treated seventh instars in feeding, residual, and topical bioassays. Fenoxycarb-treated larvae continued to molt and gain weight, and died as deformed larvae, abnormal pupae, or intermediate larval-pupal and pupal-adult forms. In feeding bioassays, fenoxycarb was more toxic to seventh instars than to first instars or adults, whereas diflubenzuron was more toxic to first instars than it was to seventh instars or adults. The feeding bioassay was more suitable for the first and seventh instars, although the residual contact bioassay could also be used for seventh instars. Adults succumbed to lower concentrations of IGRs in a topical bioassay than in feeding or residual bioassays. All three bioassay methods produced usable dose-response curves and may be used for surveying temporal changes in the IGR susceptibility to lesser mealworm.

Biological and Immune Response of <I>Galleria mellonella</I> (Lepidoptera: Pyralidae) to Sodium Tetraborate

Inorganic insecticides are commonly used in urban pest management because of their low mammalian toxicity. We tested the effects of sodium tetraborate (ST) on life parameters of greater wax moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae), to determine its sublethal toxicity on the insect. Survival, development, adult longevity, and fecundity of the wax moth were investigated by rearing larvae on artificial diets containing ST at concentrations of 0.005, 0.1, 0.2, or 0.3%. Larvae reared on medium at the highest concentration of ST (0.3%) had significantly decreased survival to the seventh instar and prolonged time required to reach the seventh instar. This concentration reduced pupa and adult yields to 12.5%, and it also prolonged development by 5 d. ST did not significantly influence adult longevity. Dietary ST led to significant decreases in fecundity and egg viability. Oviposition of survivors at the highest ST concentration (0.3%) was completely inhibited. Lysozyme content was decreased in larval hemolymph and fat body at high dietary ST concentrations. Fat body lysozyme content was significantly increased two-fold for larvae reared on diet at the lowest concentration of ST (0.005%). However, the highest concentration (0.3%) dramatically decreased fat body lysozyme content from 0.12 +/- 0.013 to 0.006 +/- 0.003 mg/ml in seventh instars. We infer that sublethal levels of dietary ST substantially influence life history parameters and immunocompetence in G. mellonella.

The ontogeny of the platycopid Keijcyoidea infralittoralis (Ostracoda: Podocopa)

Platycopid ostracods such as the genus Keijcyoidea. Malz, 1981 (Family Cytherellidae) have a unique body plan and are regarded as a phylogenetically ancient lineage. Their ontogeny, which is important in considering phylogenetical relationships, is very poorly known except for the growth of the carapace; there are nine instars including the adult, as in other podocopan groups. All appendages in all immature instars (A-8 to A-1) of Keijcyoidea infralittoralis Tsukagoshi, Okada & Horne, 2006 are described and illustrated here. The anlagen of the copulatory organs and the sexual dimorphism of carapace size appear in the sixth (A-3) instar, whereas sexual dimorphism in both the fifth and the sixth limbs, a distinctive feature of adults, is not clearly evident until the eighth (A-1) instar. Appendages are added at the moults between the second (A-7) and third (A-6), and between the fifth (A-4) and sixth (A-3) instars. The seventh limb, which platycopid ostracods have lost in the adult stage, is observed as an anlage in the sixth (A-3) and seventh (A-2) instars. During the other moults, there are no significant changes to the body plan. The ontogeny of the Platycopida is compared with that of the Podocopida, and strongly suggests that the phylogenetic position of the Platycopida is as an end-member of the Podocopa.

Penicillin-Induced Oxidative Stress: Effects on Antioxidative Response of Midgut Tissues in Instars of <I>Galleria mellonella</I>

Penicillin and other antibiotics are routinely incorporated in insect culture media. Although culturing insects in the presence of antibiotics is a decades-old practice, antibiotics can exert deleterious influences on insects. In this article, we test the hypothesis that one of the effects of dietary penicillin is to increase oxidative stress on insects. The effects of penicillin on midgut concentrations of the oxidative stress indicator malondialdehyde (MDA) and on midgut antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase [GST], and glutathione peroxidase [GPx]) and transaminases (alanine aminotransferase and aspartate aminotransferase) activities in greater wax moth, Galleria mellonella (L.), were investigated. The insects were reared from first instars on artificial diets containing 0.001, 0.01, 0.1, or 1.0 g penicillin per 100 g of diets. MDA content was significantly increased in the midgut tissues of each larval instar reared in the presence of high penicillin concentrations. Activities of antioxidant and transaminase enzymes did not show a consistent pattern with respect to penicillin concentrations in diet or age of larvae. Despite the increased penicillin-induced oxidative stress in gut tissue, antioxidant and transaminase enzymes did not correlate with oxidative stress level or between each other in larvae of other age stages except for the seventh instar. We found a significant negative correlation of MDA content with SOD and GST activities in seventh instars. SOD activity was also negatively correlated with CAT activity in seventh instars. These results suggest that exposure to dietary penicillin resulted in impaired enzymatic antioxidant defense capacity and metabolic functions in wax moth larval midgut tissues and that the resulting oxidative stress impacts midgut digestive physiology.

Penicillin-Induced Oxidative Stress: Effects on Antioxidative Response of Midgut Tissues in Instars of Galleria mellonella

Penicillin and other antibiotics are routinely incorporated in insect culture media. Although culturing insects in the presence of antibiotics is a decades-old practice, antibiotics can exert deleterious influences on insects. In this article, we test the hypothesis that one of the effects of dietary penicillin is to increase oxidative stress on insects. The effects of penicillin on midgut concentrations of the oxidative stress indicator malondialdehyde (MDA) and on midgut antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase [GST], and glutathione peroxidase [GPx]) and transaminases (alanine aminotransferase and aspartate aminotransferase) activities in greater wax moth, Galleria mellonella (L.), were investigated. The insects were reared from first instars on artificial diets containing 0.001, 0.01, 0.1, or 1.0 g penicillin per 100 g of diets. MDA content was significantly increased in the midgut tissues of each larval instar reared in the presence of high penicillin concentrations. Activities of antioxidant and transaminase enzymes did not show a consistent pattern with respect to penicillin concentrations in diet or age of larvae. Despite the increased penicillin-induced oxidative stress in gut tissue, antioxidant and transaminase enzymes did not correlate with oxidative stress level or between each other in larvae of other age stages except for the seventh instar. We found a significant negative correlation of MDA content with SOD and GST activities in seventh instars. SOD activity was also negatively correlated with CAT activity in seventh instars. These results suggest that exposure to dietary penicillin resulted in impaired enzymatic antioxidant defense capacity and metabolic functions in wax moth larval midgut tissues and that the resulting oxidative stress impacts midgut digestive physiology.

Number of Instars and Stadium Duration of <I>Gynaephora menyuanensis</I> (Lepidoptera: Lymantriidae) from Qinghai-Tibetan Plateau in China

Abstract On the basis of head capsule widths (HCWs) of field-collected and laboratory-reared larvae, the moth Gynaephora menyuanensis Yan & Chou (1997) (Lepidoptera: Lymantriidae) was first found to have six instars in the male and seven instars in the female. Mean HCWs were 0.68, 0.91, 1.22, 1.58, 2.06, 2.69, and 3.45 mm in field-collected larvae and 0.67, 0.87, 1.17, 1.54, 2.00, 2.59, and 3.24 mm in laboratory-reared larvae for first through seventh instars, respectively. Stadium duration, body length, and body mass of each instar also were examined. The first, second, third, fourth, fifth, sixth (♀, ♂), and seventh (♀) instars averaged 240.30, 15.32, 14.58, 14.74, 13.86, 15.90 (♂), 13.65 (♀) and 16.28 (♀) d in stadium duration; 3.95, 4.96, 6.07, 9.14, 13.31, 17.23, and 25.79 mm in body length; and 1.33, 3.46, 7.79, 17.32, 45.05, 103.07, and 217.24 mg in body mass under the field conditions. Analyses of the results showed highly significant exponential correlations of HCW with body length and body mass,...

Levantamento de espécies de Odonata associadas à tanques de piscicultura e efeito de Bacillus thuringiensis var. israelensis sobre ninfas de Pantala flavescens (Fabricius, 1798) (Odonata: Libellulidae

Several psiculture stations that deal with fingerlings or ornamental fishes rearing have presented some problems with larvae preying, post-larvae and fingerlings by Odonata Order insect nymphs. Thus, the aim of this work was to survey the Odonata species present in fish-raising tanks in two towns of the Midwest region of Minas Gerais, and also to evaluate the effect of Bacillus thuringiensis var. Barjac israelensis on Pantala flavescens nymphs (Fabricius, 1798) (Odonata: Libellulidae). Fortnightly collections were performed over a three month period. The adult insects were captured with entomological nets and the nymphs with fine mesh sieves, coupled to wooden handles. The captured nymphs were taken to the laboratory where they were individualized in 2L plastic foam boxes and sealed in its upper extremity with tulle. Soon after the adults emergence, they were killed, packed into envelopes and sent to be identified. The laboratory experiments were conducted in an acclimatized room at 25 ± 2°C, RH of 70 ± 10% and 12-hour photophase. Second instar P. flavescens nymphs were packed individually into plastic foam boxes containing 500mL of chlorine free water each one. When they were in the third, fifth and seventh instars, they were treated with B. thuringiensis var. israelensis through the microbial product Vectobac® in granulate formulation. The product was directly applied to the rearing container water at the concentration denoted for the control of culicidae larvae, two superior concentrations, two inferior and also another one, where the product was not applied. The evaluations were done at 24, 48 and 72 hours after the product application, recording the dead insects number in each treatment. In both experiments, the nymphs were fed with Culicidae larvae and new-born fishes of the species Poecilia cf. vivipara Schneider, 1801. The following species were identified: Ischnura fluvialis Selys, 1876; Aphylla theodorina (Navas, 1933); Brachymesia furcata (Hagen, 1861); Erythrodiplax fusca (Rambur, 1842); Miathyria marcella (Selys, 1857); Micrathyria almeidai Santos, 1945; Micrathyria hesperis Ris, 1911; Orthemis discolor (Burmeister, 1839); Perithemis mooma Kirby, 1889 and P. flavescens. There were no significant microbial product effects on the studied species

Susceptibility of Asian longhorned beetle, Anoplophora glabripennis (Motchulsky) (Coleoptera: Cerambycidae) to entomopathogenic nematodes

Isolates of Steinernema feltiae SN from France, Steinernema glaseri NJ from New Jersey, Steinernema riobrave TX from Texas, Steinernema carpocapsae Sal from Indiana, S. carpocapsae All from Georgia, and Heterorhabditis marelata IN from Indiana were screened for efficacy against laboratory colonies of Asian longhorned beetle, Anoplophora, glabripennis collected from Queens, New York and Chicago, Illinois. Two bioassays were used to screen nematode effects on beetle larvae; a filter paper assay using a 24-h exposure of nematode-to-target-insect, and a diet cup bioassay using a 72-h exposure of host larvae to infective juveniles applied to the larval bore hole made in the artificial diet in the cups. First- and third-stage larvae were susceptible to all isolates using a filter paper bioassay. S. feltiae and S. carpocapsae Sal were the most effective, causing 100% mortality. S. feltiae was more infectious than S. carpocapsae Sal against third, sixth, and seventh instars. S. riobrave, S. glaseri, and H. marelata were ineffective against the older instars. In the diet cup bioassay, S. feltiae and S. carpocapsae Sal killed 71–100% of mid-to late instar larvae, but the remaining isolates screened were ineffective. Nematode preconditioning to aqueous A. glabripennis frass extracts inhibited S. carpocapsae Sal infectivity but had no effect on nematode pathogenicity. S. feltiae juveniles were positively attracted to A. glabripennis frass extracts. Our results demonstrate the potential use of S. feltiae and S. carpocapsae isolates as control agents for A. glabripennis. Published by Elsevier Inc.

1-Octen-3-ol together with geosmin: new secretion compounds from a polydesmid millipede, Niponia nodulosa.

The small millipede Niponia nodulosa (Polydesmida: Cryptodesmidae) emits an earthy smell when disturbed. This smell was obtained from hexane extracts from both sexes at the sixth and seventh instars and adult stages, and was found by GC/MS analyses to be composed of two compounds, 1-octen-3-ol as the major component and geosmin as the minor component. This is the first report of these compounds in secreted substances from millipedes. As they showed little repellent activity against foraging ants in bioassays, their biological function as defensive allomones was not clearly elucidated. However, both compounds provoked negative chemotaxis of conspecific millipedes in a Y-tube olfactometer, especially 1-octen-3-ol, which was active at a dose equivalent to the content of a single millipede. Such biological activity suggests that this compound is involved in intraspecific communication in this millipede and may play a role as an alarm pheromone.

Beauveria bassiana (Balsamo) Vuillemin - a Promising Microbial Control Agent of the Satin Moth (Lepidoptera: Lymantriidae)

A new isolate of the entomopathogenic fungus, Beauveria bassiana , was tested by laboratory bioassays for potential use as a microbial control agent of the early (third) and last (seventh) instars of the satin moth, Leucoma salicis L. Results demonstrate that this fungus is very effective against last instars of this lepidopteran pest. Although B. bassiana was cultured successfully from internal contents of all cadavers examined, vegetative hyphae emerged from intact cadavers of L. salicis infected as early (third) instar caterpillars only.

Density‐Dependent Settler‐Recruit‐Juvenile Relationships in Blue Crabs

Current theory on the population dynamics of marine species with complex life history patterns posits that a suite of physical and biotic forces (e.g., habitat structure and density—dependent predation or emigration) control survival and abundance in early life history, particularly after settlement. We have conducted a long—term sampling effort accompanied by a series of field and laboratory experiments examining the joint effects of habitat type, body size, and population density upon abundance and survival of early juveniles of the blue crab, Callinectes sapidus. In addition, the chance occurrence of a tropical storm during one set of experiments provided an opportunity to assess the impact of a physical disturbance upon newly settled blue crab survival and abundance. In the 10—yr sampling effort, we quantified relationships between sequential life history stages (juvenile crab instars) in seagrass beds, the initial nursery habitat for blue crabs in the lower Chesapeake Bay. Inter—instar relationships were defined as the densities of larger instars as dependent on the densities of smaller instars. Inter—instar relationships for the youngest instars are described by hyperbolic functions until crabs begin to emigrate to unvegetated habitats at approximately the fifth instar. Inter—instar relationships between crabs larger than the fifth instar and smaller crabs become either parabolic or linear functions and decay as the number of instars between sequential life history stages increases. While both the hyperbolic and parabolic functions are indicative of populations regulated by density—dependent processes, either predation or emigration, the decay in the functions describing the inter—instar relationships for crabs larger than the fifth instar indicates that the suite of processes regulating this segment of the population changes qualitatively. In laboratory and field experiments, the effects of vegetated and unvegetated habitats and size—specific predation on newly settled juveniles were tested. Tethering was used to quantify relative rates of predation, and a laboratory study was conducted to determine if tethering induced treatment—specific bias. We found no statistically significant interactions between the tethering treatment and the factor treatments of crab size and habitat during the laboratory study, indicating that tethering did not produce treatment—specific bias. Thus, tethering provided a relative measure of predation that allowed comparisons between treatments of habitat and crab size on crab survival. In both laboratory and field experiments, survival was significantly higher in vegetated habitats and with increasing size until the ninth instar, when survival did not differ by habitat. This difference explains the dispersal from vegetated to unvegetated habitats that occurred between the fifth and seventh instars. In addition, survival of all crabs was significantly increased both during and after Tropical Storm Danielle compared to pre—storm conditions. A model is developed that describes juvenile survival as a function of crab size and habitat type. Survival curves in both habitats are represented by similar sigmoid functions with survival higher in vegetated habitats. Subsequently, the survival of newly settled blue crabs is likely dependent on the availability of complex habitat. Thus, a suite of biotic and physical processes, both density—dependent and density—independent, control the early life history after settlement for the blue crab.

Temporal polyethism in incipient colonies of the primitive termiteZootermopsis angusticollis: A single multiage caste

Division of labor was studied in incipient colonies of the dampwood termite Zootermopsis angusticollisby recording repertoire size, behavior frequencies, and time budgets of larvae. Behavioral repertoire size increased with age: first- and secondinstar larvae were mainly inactive, whereas larvae of the third through seventh instars performed 64–100% of all tasks. The increase in repertoire size from the second to the third instar was abrupt; repertoire size and composition remained more or less constant for older instars. No correlation between age (instars III–VII) and tasks was identified, suggesting that colony labor is performed by a single functional caste that spans the third to the seventh instar without any age-based division of labor. Small colony size, low oviposition rate, simple nest architecture, a lack of spatial association of tasks, and the potential for attaining reproductive status appear to be associated with the lack of age-related behavioral specialization in Z. angusticollis.In effect, the absence of temporal polyethism in this species is likely a consequence of its nesting habits and physiological and developmental constraints.

Biology of Tricrania stansburyi, a Meloid Beetle Cleptoparasite of the Bee Osmia lignaria propinqua (Hymenoptera: Megachilidae)

A life-cycle chronology of Tricrania stansburyi (Haldeman) developed from results obtained in this study demonstrates that this meloid species is univoltine, individuals mate more than once as they emerge from host nests, dispersal is accomplished by flight, adults apparently do not feed and are short-lived (1–2 wk), fecundity is high (>900 eggs per female), parasitism is accomplished through phoresy by the first instar (triungulin), meloid larvae develop through seven instars, the entire host cell provision is consumed by the first five instars (sixth and seventh instars do not feed), and only one meloid larva survives multiple parasitism of any host cell. Results were also obtained on courtship, mating, sex ratio (female-biased), preferred egg deposition sites, new host records (7 species), preferential discrimination of triungulins to various host species, function of silken strands produced by triungulins, environmental triggers that initiate combat between triungulins, and biological traits that influence annual rates of parasitism by T. stansburyi .

Larval Instars and Growth Pattern of a Univoltine Black Fly, Prosimulium kiotoense (Diptera: Simuliidae), in Kyushu, Japan

Seven larval instars were detected for a natural population of Prosimulium kiotoense Shiraki in Kyushu, Japan, from the size frequency distribution of postgenal lengths. Growth in P. kiotoense larvae followed a geometric progression from first to sixth instars, but the size ratio between sixth and seventh instars was smaller than between other successive stadia. The linear relationship between the mean instar value and daily cumulative water temperature indicated that development between instars required 82.6 degree-days (DD). The accumulated temperature for larval development of this species was estimated to be 600 DD.

Flow-cytometric analysis of spermatogenesis in Teleogryllus commodus

The development of the testis of the cricket Teleogryllus commodus has been studied using flow cytometry. From a laboratory-reared population of insects, total testis tissue was prepared at approx. 48-h intervals for the entire development period extending from the fifth instar (28 days after eclosion) to the imaginal moult (about 60 days after eclosion). Cells were stained with DNA-specific fluorochromes and the temporal sequence of the development of the testis as well as the timing of specific meiotic events quantitatively determined. Testis development studied in this fashion is seen as changes in the relative frequency of cells with 1, 2, and 4C DNA content. Pre-spermiogenic processes of spermatogenesis (change in the frequency of cells with 2 and 4C DNA content) occur continuously during the fifth-eighth instars, while the appearance of 1C cells (initiation of spermiogenesis) occurs abruptly at the transition between the sixth and seventh instars.

Temperature Requirements for Development of the Jack Pine Bud worm (Lepidoptera: Tortricidae) and Two of Its Parasitoids (Hymenoptera)

Rates of development at various constant temperatures were determined for immature stages of jack pine bud worm, Choristoneura pinus pinus Freeman, and two parasitoids of its overwintering stage, Apanteles fumiferanae (Viereck) and Glypta fumi-feranae Viereck . Jack pine bud worm larvae ( JPB ) required 416 degree-days ( DD ) above 7.5°C for development from emergence of second instars to pupation, while the pupal stage required 129 DD above 8.0°C. The second through the seventh instars required 70.8, 54.5, 55.5, 58.7, 72.8, and 115.3DD above 7.5°C, respectively. Males developed faster than females during the fifth, sixth, and seventh instars, but females developed faster during the pupal stage. This resulted in synchronized emergence of adults of each sex. Parasitism by A. fumiferanae (AF) slowed development of JPB second, third, fourth, and fifth instars by 2.9, 4.2, 11.1, and 24.5 DD above 7.5°C, respectively. JPB parasitized by G. fumiferanae (GF) spent 5.3, 7.1, and 11.3 DD above 7.5°C longer as fourth, fifth, and sixth instars than unparasitized JPB. Larval AF required 352 DD above 7.3°C for development from emergence of second instars to parasite emergence from the host. Pupae required 108 DD above 9.7°C. GF larvae required 485 DD above 6.1°C, and pupae required 167 DD above 7.7°C. These resultssuggestthat parasitism will affect phenology of JPB in the field. Some recommendations for management of JPB populations that consider parasitoid development and conservation of natural enemies are given.

Some Observations on Chilo partellus (Lepidoptera: Pyralidae) Developmental Biology under Field and Laboratory Conditions

Observations on the growth and development of Chilo partellus (Swinhoe) larvae under laboratory and field conditions indicate sexual dimorphism as well as a general developmental polymorphism. Larvae of both sexes went through fifth, sixth or seventh instars before pupation. The mean developmental period, larval head capsule width, and the number of instars before pupation as well as pupal weight were higher in the female compared to the male larvae. These observations suggest differences in the physiological state of fifth-instar larvae in a population; some of them might be in the penultimate, while others might be in the ultimate instar.

Isolation of two cDNA clones coding for larval hemolymph proteins of Galleria mellonella

Galleria mellonella a group of four larval hemolymph proteins (LHP) (74, 76, 81 and 82 kDa), which had been earlier shown to be storage proteins, exhibit a stage-specific synthetic pattern. The 82 kDa LHP is synthesized only in day-3 to day-5 last instar larvae, while the other three LHPs are synthesized both in the penultimate (six) and the last instar larvae. None of these LHPs are synthesized in day-0 last instar. With a view to isolate one or more cDNA clones corresponding to these LHPs a cDNA library was prepared in pBR322 starting with poly(A) + RNA from day-5 last instar larval fat body. By differential screening of 714 clones with poly(A) + RNA 39 day-5 larval stage-specific clones were isolated. Two of these clones, designated as 26–38 and 17–36, had 1200–1300 base pair cDNA inserts. Their cDNA inserts did cross hybridize to each other, exhibited different restriction endonuclease digestion patterns and hybridized in northern blots to transcrips of different sizes, thereby suggesting that they represent two separate genes. In addition, the genomic fragments that hybridized in southern blots to the two cDNAs differed in their size. On translation, mRNAs hybrid selected by 26–38 and 17–36 cDNAs produced 76 and 79 kDa polypeptides respectively. Both these genes are expressed in the fat body but not in the midgut, silk glands, Malpighian tubules or carcass. While 26–38 was expressed both in the sixth and seventh (last) instars, 17–36 was expressed only in the last instar. On the basis of tissue and developmental stage specificity of their expression and the sizes of their hybrid selected translation products, these clones are tentatively identified as two LHP-specific cDNA clones. The genes coding for these LHPs appear to be single copy genes.

A population study of the coconut pest Segestidea uniformis (Willemse) (Orthoptera: Tettigoniidae) on an equatorial island

AbstractA population of the coconut pest Segestidea uniformis (Willemse) was monitored on a small island 2° from the equator in Papua New Guinea between 1973 and 1978. Totals of 54 000 first-instar nymphs were caught on sticky traps on palm trunks and 8750 other nymphs and adults were recovered from the crowns of palms. Generations were completely overlapping, and there was no evidence of seasonality in population fluctuations. The sex ratio was 50:50 in the first six instars, but 90% of seventh instars and 30% of adults were female. Explanations for these variations are given. The population declined from an annual mean of 24 individuals of all ages per palm crown in 1973 to 9 in 1976 and increased again to 29 in 1978. Most post-hatching mortality occurred as first instars climbed from the ground to the crown of palms, probably due to the lizard Gehyra oceanica and rainfall. The number of adults was more sensitive to mortality occurring after the first instars had arrived in the crowns. This mortality appeared to be related to the duration of periods without rainfall, supporting earlier observations that damaging outbreaks of S. uniformis populations do not occur in places which experience a regular dry season. Production of coconuts appeared to be inversely related to the population density of S. uniformis, which did not rise above a level estimated to cause 20% defoliation of the palms during the study. Nut production also seemed to be related to the number of hours of sunshine received in the preceding 12 months. Biological control aimed at nymphs and adults in palm crowns is suggested as an option for controlling S. uniformis which deserves investigation.