Number Of Instars Research Articles

Larval Instars and Adult Flight Period of Monochamus saltuarius (Coleoptera: Cerambycidae)

Monochamus saltuarius is a vector of Bursaphelenchus xylophilus in Japan, South Korea, and the middle temperate zone of China. However, there are only a few reports on this species in China, and its biological characteristics are still unclear. In this study, we aimed to elucidate the larval development and adult flight period of M. saltuarius to provide a theoretical basis for the effective control of pine wilt disease in the middle temperate zone of China. Seven morphological variables of larvae were measured to determine the number of larval instars, and the adult specimens of M. saltuarius were collected from traps in forests to study the flight period of adults in Fushun, Liaoning, the epidemic center of pine wilt disease in the middle temperate zone of China. The results revealed that the full larval period of M. saltuarius was 279.6 d, and the larvae had five instar stages, with an average duration of 7.4, 14.3, 49.8, 83.6, and 124.5 d, respectively. Additionally, 78.4% of the overwintering larvae were fourth instar, and 21.6% were fifth instar larvae. We also found that the adults began to emerge from early May to late June, and the period was from early May to mid-August in the forest. During the investigations period from 2018 to 2020, the total number of adults captured was minimal at 744, and precipitation was highest at 291.54 mm in 2019. We characterized the larval instars and adult flight period of M. saltuarius, which is a prerequisite for developing appropriate management strategies. The results of this study will provide an important reference for the formulation of strategies to control M. saltuarius and pine wilt disease.

Captive breeding of odonate larvae: Effects of type of water, handling, and sex

AbstractBasic information on life histories, ecology, and behaviour for aquatic stages in many species of insects is difficult to obtain in the field. Here, a method to breed and monitor individual Odonata larvae in captivity is proposed. In total, 3788 individuals of six Odonata species – Rhionaeschna marchali (Rambur), Erythrodiplax abjecta (Rambur), Sympetrum gilvum (Selys), Ischnura chingaza Realpe, Ischnura cruzi De Marmels, and Mesamphiagrion laterale (Selys) – were reared individually in water‐filled plastic containers, whose size was increased to fit larval growth, at ambient temperature (12–34 °C, 12 h light per day, ca. 300 lux, and ad libitum food). We tested the effects of water type (habitat water, dechlorinated tap water, and drinking water), handling method, and sex on larval developmental time and number of instars. The number of instars was calculated as the mean number of moults for the individuals that successfully emerged as adults. Life cycle length was calculated by averaging the days over individuals that completed their development until emergence. The probability of achieving the adult stage was not significantly affected by the type of water, sex, or handling method. On the other hand, the number of instars was affected by species identity, and type of water, with fewer instars in water from the natural habitat, but not affected by sex or handling method. The duration of the life cycle was bimodal in most species, and was affected by type of water, but in an idiosyncratic, species‐specific way. The methodology proposed here allows monitoring and breeding large numbers of odonate larvae.

Development of Azalea Lace Bug, Stephanitis pyrioides, on Susceptible and Resistant Rhododendron species in Western Washington.

The invasive azalea lace bug, Stephanitis pyrioides (Scott) (Tingidae: Hemiptera), is an important pest of Rhododendron (L.) (Ericales: Ericaceae). Feeding by nymphs and adults removes chlorophyll, reduces rates of photosynthesis and transpiration, and causes leaf stippling, which reduces the aesthetic value of infested plants. Rhododendron spp. are a major component of landscapes in the Pacific Northwest. Previous studies on the seasonality of S. pyrioides in North America are largely from the southeastern United States, which could have limited applicability in the Pacific Northwest. To quantify S. pyrioides seasonality in western Washington, we sampled ~200 leaves from 18 Rhododendron plants 1-2 times per wk from April to October over 2 yr, and microscopically counted the number of eggs, early instars, late instars, and adults. We developed a degree-day model for first generation S. pyrioides, which we used to estimate that S. pyrioides undergoes two full and a partial third generation in western Washington. Our model estimates 5 and 50% early instar occurrence, after hatching from overwintering eggs, at 69 and 171 accumulated degree-days from 1 January, respectively, when using a base threshold of 10.2°, which can be used to optimize the timing of management decisions. We also observed faster development and adult emergence when S. pyrioides nymphs feed on susceptible host plants relative to more resistant host plants, which may influence the timing of management decisions and potentially increase the probability of a full third generation. This research enhances our knowledge of an emerging invasive species in the Pacific Northwest.

The Prepupa of Calindoea trifascialis (Lepidoptera, Thyrididae)

A prepupa is a non-feeding stage that occurs between the final feeding larval instar and the pupa. It is less common in Lepidoptera because most species pass relatively directly from feeding cessation to pupation. This paper describes the occurrence of such a stage in the thyridid moth, Calindoea trifascialis (Moore). The prepupa is primarily a functional designation based on attributes associated with an extended wandering phase. The distinctness of this stage was demarcated by observed changes in the integument at the transition point to the prepupa. It was also corroborated by morphometric comparisons of length and mass with the final feeding instar. Measures of head capsule width indicated a potential stage-based departure from the Brooks-Dyar rule. The model fit changed with the number of instars assigned to the life cycle and depending on whether the prepupa was considered as a distinct instar. In the latter case the deviation was marked; but with the prepupa excluded, the growth curves still hinted at compensatory adjustments to growth increment prior to the non-feeding period. Molting was cryptic as a result of the use of leaf shelters and the consumption of exuviae after ecdysis.

Head Capsule Width, Body Weight and Length Measurements for Instar Determination in Mason Bee (Osmia cornifrons) Larvae

Osmia cornifrons is a cavity-nesting solitary species used as an apple pollinator in Korea. We collected Osmia spp larvae to examine potential correlations of larval stage. The head widths of from 1<SUP>st</SUP> to the 5<SUP>th</SUP> instar ranged from 0.4±0.1 to 1.3±0.3 mm, and growth rate of each instar was significantly highest between 1<SUP>st</SUP> and the 2<SUP>nd</SUP> instar. The fitness regression model for the head capsule width was analyzed. The head capsule width plotted against the number of instars resulted in a regression line of y=0.146x+0.551, R²=0.838. The body weights of the larvae increased with larval developmental stage, and the coefficient of variation of larval weights was high. However, the calculated regression line was y=5.122x² -12.154x+11.444, R²=0.900. The growth ratio of the larval length was clearly maximal between the 3<SUP>rd</SUP> and 4<SUP>th</SUP> instars, while that of 5<SUP>th</SUP> instar larvae was decreased. The calculated regression line is y=2.595x+0.472, R²=0.920. The result suggests that measurements of head capsule width, weight and length may be useful as a method to determine larval instar.

Epicuticular Wax Rice Mutants Show Reduced Resistance to Rice Water Weevil (Coleoptera: Curculionidae) and Fall Armyworm (Lepidoptera: Noctuidae).

Plant structural traits can act as barriers for herbivore attachment, feeding, and oviposition. In particular, epicuticular waxes (EWs) on the aerial surfaces of many land plants offer protection from biotic and abiotic stresses. In rice (Oryza sativa L.), mutations that reduce EWs have been previously reported. However, whether such mutations affect rice water weevil (Lissorhoptrus oryzophilus Kuschel) and fall armyworm (Spodoptera frugiperda Smith) performance has not been investigated yet. These pests cause significant economic problems in important rice-producing areas of the United States. The aim of our study was to characterize the EWs of EW mutants and wild-type rice plants by gas chromatography–mass spectrometry and compare the resistance of mutant and wild-type plants against rice water weevil and fall armyworm. We hypothesized that mutants with reduced EWs would have weaker resistance to pests than wild-type plants. Three mutant lines (6-1A, 7-17A, and 11-39A) and their wild-type parent (cv. ‘Sabine’) were used to test this hypothesis. Levels of EWs were significantly lower in mutant lines than in the wild-type, and qualitative differences in EW composition were also observed. Reduction in EWs significantly affected performance of insects in experiments conducted under greenhouse conditions. Experiments with rice water weevils were conducted in arenas in which females were given a choice of the mutants and the wild-type for oviposition. Number of first instars emerging from the three EW mutants (an indication of oviposition preference) was higher on the three EW mutants than on wild-type plants with normal wax levels. Similarly, in no-choice experiments using whole plants or detached leaves, weight gains of armyworms on leaves were higher on the mutant lines than on the wild-type. These results indicate that EW traits are involved in rice resistance to weevils and armyworms. Understanding the plant traits that contribute to resistance to rice pests will be helpful for the development of resistant varieties for reducing pest insect damage.

Subtle life cycle differences between two sympatric Mesosemia (Lepidoptera: Riodinidae) butterflies

ABSTRACT The natural history and morphology of two sympatric species of Rubiaceae-feeding metalmark butterflies, Mesosemia m. machaera and Mesosemia philocles jeziela, are described and illustrated using both light and scanning electron microscopy. These species use the same Rubiaceae host plant species and have similar life cycles. Single eggs are laid on old leaves, caterpillars are solitary, and pupation occurs off the host plant. Differences occur during ontogeny with caterpillars using different host plant parts, M. m. machaera feeds on the abaxial leaf surface and M. philocles jeziela on the new leaves and adaxial surface. There is also variation in the number of instars, size and number of setae and details in larval and pupal color patterns. Caterpillars are non-myrmecophilous and have defense-related tentacle nectary organs (TNOs), the functionality of this organ in pupae is recorded for the first time. These results show that although similar, subtle differences exist in the Mesosemia life cycles.

Naupliar development of Facetotecta (Crustacea: Thecostraca) and the nature of the first nauplius instar in the Crustacea - pro et contra the Hexanauplia concept

From a number of partial moult series obtained by laboratory culture of plankton-caught specimens, we described all naupliar instars of the facetotectan species, Hansenocaris itoi. It reveals seven naupliar instars, instead of the five that were previously supposed for the Facetotecta. This number of naupliar instars is unique not only for Facetotecta, but also for Thecostraca and Hexanauplia as well. We studied the external morphology of each naupliar instar in detail with light microscopy and SEM. Nauplius 1 is entirely non-feeding and differs from subsequent instars in having a smooth, unsculptured cuticle and undeveloped armament of the labrum and the limbs. The subsequent naupliar development is characterized by an increase in size and in the number of cuticular plates and by the appearance of different armament of the limbs. We compare nauplius 1 across all Thecostraca and discuss its nature in relation to the larval development of Crustacea. We also discuss the presence of seven naupliar instars in Facetotecta and the concept of Hexanauplia.

EFFECTS OF ARTIFICIAL DIETS ON THE BIOLOGICAL CYCLE OF Condylorrhiza vestigialis

The objective of this work was to determine the influence of different artificial diets on biological parameters related to the life cycle of C Condylorrhiza vestigialis aiming to determine the most suitable diet for the rearing of a population of this insect. Four diet formulations were tested. Ten repetitions were used, with 30 caterpillars per repetition. All stages of C. vestigialis life cycle were followed to evaluate biological parameters: viability of larvae, pre pupa, pupa and adults, as well as the sex ratio. The number of larval instars, the pupal mass and the total number of eggs per day and per female day were also calculated. The four diets tested allowed the development of C. vestigialis caterpillars. All diets were considered adequate for the purpose of the work, which is the production of baculovirus used in the control program of this pest. It was the diet 2 that provided the best results, the largest pupal mass, and the quantity and viability of the eggs produced by C. vestigialis females fed in this larval phase.

Direction, ontogeny, and mechanism of the temperature-size rule operating in a large marine crab, Chionoecetes opilio

Abstract The classic temperature-size rule (TSR) states that ectotherms mature smaller in warmer than in colder conditions; the reverse TSR is the opposite response. We combined field observations with laboratory experiments and published information to synthesise the response of snow crab (Chionoecetes opilio), a marine brachyuran with determinate growth, to temperature. Size at onset of physiological maturation/maturity and after terminal moult (TM) were positively related to temperature, thus indicating the reverse TSR. Moult increment varied little with temperature, but crabs were larger at instar in colder than in warmer water due to an initial difference in settlement size that propagated to higher instars, suggesting classic TSR prior to settlement. The pattern of increasing TM size with temperature was caused by crabs moulting more times before TM in warmer than in colder water. Intermoult period (IP) declined exponentially with temperature, and lower instars were more temperature sensitive than higher instars. Temperature effects on IP were strong enough to explain changes in size and instar number at TM under a possible time-invariant maturation schedule. Skip moulting was observed in the smallest crabs reared in the laboratory and resulted in high mortality. The reverse TSR in snow crab seems to be adaptive to coping with ectotherm predation.

Instar determination for sugarcane internode borer Chilo sacchariphagus indicus (Kapur) (Lepidoptera: Crambidae)

• Sugarcane internode borer (INB) passes through five larval instars to become a pupa. • Frequency distribution of head capsule widths is reliable in instar fixation in INB. • Dyar’s ratios and regression analyses confirmed that no instar has been overlooked. • The probability of misclassifying an INB instar into another is remote (0.16–1.97%). Internode borer (INB), Chilo sacchariphagus indicus has been a serious threat to sugarcane cultivation for more than six decades. We have determined the number of instars for INB through frequency distribution analysis of cast head capsule widths. This is the first report, which proves that the INB of sugarcane passes through five larval instars to attain its pupal stage. The number of instars determined by kernel density estimation was in corroboration with the number of instars observed in the laboratory. The mean Dyar’s ratios for both the instar-wise observed data on head capsule widths and the theoretical data derived from the frequency distribution analysis were one and the same (1.46). Linear regression (R 2 > 0.998) between the instar numbers and their corresponding mean head capsule widths reaffirmed that no instar has been overlooked. Further, the theoretical misclassification probabilities of 0.16–1.97% indicates that the chance of misidentifying an INB instar into its preceding or succeeding one is very remote. Since the determination of the exact number of instars in a pest species is a pre-requisite for developing appropriate management strategies, the outcome of this study holds great promise in managing the most notorious Crambid borer of sugarcane.

A new direction to understand the life cycle of the Japanese pine sawyer considering the selection strategy of instar pathways

The Japanese pine sawyer, Monochamus alternatus Hope (Coleoptera: Cerambycidae), transfers the pine wood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer) that causes pine wilt disease (PWD), especially in Asian countries. The key for the control of PWD is primarily focused on vector management. Thus, understanding the exact life history of M. alternatus is required. Since the late 1980s, the life cycle of M. alternatus has been accepted under the assumption that the final larvae pass four instars in the field. This study is revising the previous error for the life cycle hypothesis of M. alternatus by finding various instar pathways, which pathway is defined as the number of instars that larvae pass through prior to pupation. We confirm experimentally that the overwintered fourth or fifth instar larvae directly pupate to emerge as adults, indicating the presence of four and five instar pathways, respectively. The selection of instar pathway might be determined primarily by habitat temperature. This information will be useful to explain the variation of life history in M. alternatus populations worldwide based on the thermal environments, and also can be served to predict the northern distribution limit by applying the threshold degree-days for the completion of four instar pathway.

Per‐stage growth rates of head and body sizes in scarab larvae (Coleoptera: Scarabaeidae) decrease across ontogeny following a species‐specific pattern

AbstractIt has been widely assumed that the stepwise increase in the exoskeleton size of larval insects approximately follows a geometric progression from instar to instar, known as Dyar's Rule. However, it is not clear whether the per‐instar increase in body size follows this rule. In insects, Dyar's Rule has been identified either by regressing the log‐scaled size on the instar number (log‐linear regression analysis) or by comparing the postmolt/premolt size ratio between instars (growth rate analysis). A previous study on the body mass of caterpillars showed the methodological pitfall that Dyar's Rule was statistically supported by log‐linear regression analysis, but not at all by growth rates analysis. I considered this concern here by examining the per‐stage growth rates of head and body sizes for larvae of the beetle Trypoxylus dichotomus using both methods and compared the resulting growth rates for body size within and between taxonomic orders. Dyar's Rule was statistically supported by the log‐linear regression analysis but not by growth rate analysis for both the head and body sizes in T. dichotomus. The body size growth rate in T. dichotomus decreased as the instar progressed. This developmental pattern was also found in reported data for the other six scarabs, but not in data for Lepidoptera or Hymenoptera. These findings confirm that the per‐stage growth rate of body size does not follow Dyar's Rule in a wide range of insects, and suggest that developmental change in the body size growth rate varies among insect groups.

Sublethal Effects of Malathion on Biology and Population Growth of Khapra Beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae)

Khapra beetle, Trogoderma granarium Everts is a serious pest that affects stored grains and oilseeds. The current work was carried out to investigate the effect of malathion sublethal concentrations (LC10 and LC40) exposed to first and fourth larval instars on biological aspects and population growth of T. granarium. Results indicated that exposure of 1-st instar to either LC10 or LC40 had a destructive effect and treated larvae failed to complete their larval stage. While 4-th instar exposed to the same sublethal concentrations completed their life cycle with considerable impacts on biological aspects and life table parameters. Treatments increased the number of instars molting reaching seven or eightinstars. In contrast, larval, pre-adult, and total longevity periods were decreased in treatments compared with control. Concerning life table parameters such as net reproductive rate (R0), intrinsic rates of increase (r), finite rate (λ), fecundity and mean generation time (T) were decreased compared to control. The current study clarified thatsublethal concentrations of malathion induce strong adverse effects and suppress the population growth of T. granarium. Our results would be useful to assess the overall effects of malathion on T. granarium and can contribute effectively in pest management.

Rearing enhancement of Ovalipes trimaculatus (Crustacea: Portunidae) zoea I by feeding on Artemia persimilis nauplii enriched with alternative microalgal diets

The southern surf crab Ovalipes trimaculatus (de Haan, 1833) presents a high potential for aquaculture. In this study, we analyze the benefits of different dietary treatments on its molt success and fitness of larval stages. Artemia persimilis nauplii were enriched with monospecific (Nannochloropsis oculata, Tetraselmis suecica, Dunaliella salina, Isochrysis galbana and Chaetoceros gracilis) and multispecific (Mix) microalgal diets twice a day over a 48-h period. Mean total length (TL), growth instar number (I) and gut fullness rate (GFR) of nauplii showed significant differences between dietary treatments at several sampling times, optimal results being observed in those providing Mix. Artemia nauplii grown under most experimental dietary treatments reached the capture size limit for Ovalipes trimaculatus zoea I (700 µm) within 24 h. After that time interval, Mix-enriched nauplii were amongst those with higher protein contents. Ovalipes trimaculatus zoea I fed on Artemia nauplii enriched during 24 h under different dietary treatments showed significant differences in survival, inter-molt duration, molting success to zoea II and motility. Optimal results were observed in zoea I fed on Mix-enriched Artemia nauplii. This work not only represents a first step towards the dietary optimization for O. trimaculatus zoeae rearing but also provides the first results on the use of enriched A. persimilis.

Notes on Brood Morphology and the Development of the Neotropical Eusocial Wasp Mischocyttarus cerberus (Hymenoptera, Vespidae, Polistinae)

Mischocyttarus cerberus stands out among the most investigated species of the eusocial paper wasp, in Brazil. While the adult characteristics were relatively well reported in the earlier studies, very meager information was available regarding their immature stages. This study provides a description of the immature morphology of the general brood of M. cerberus, by studying the number of instars and analyzing the degree of influence exerted by some of the environmental factors on the individuals in the immature phases. This work involves a detailed study of 72 wasp colonies from Rio Claro and Ribeirão Preto. Using the larvae drawn from 41 nests, the number of instars was calculated; besides, the degree to which a few environmental factors could affect the immature brood development was assessed in 31 nests. Eggs showed patterns similar in terms of form and size to that of the species described earlier. The two ventral lobes, characteristic of the Mischocyttarus larvae, were fully developed only in the fifth instar. The measurements of the larval heads in the five instars found concurred with the earlier reports for most of the social wasps. Furthermore, the larval stages took longer to develop, which could be related to the greater susceptibility of the larvae to the prevailing environmental factors. From the results of our study, we concluded that the M. cerberus showed the typical developmental pattern in the immature stages of its genus.

Development of Helicoverpa armigera (Hübner, 1805) and Spodoptera frugiperda (SMITH, 1797) in winter forages

Helicoverpa armigera (Hübner, 1805) and Spodoptera frugiperda (Smith, 1797) are polyphagous pests of great agricultural importance in subtropical and temperate climate regions. The usual management of production areas in the southern region of Brazil occurs after the harvesting of summer crops, and the areas are sown with pasture. Thus, forages recommended for grazing are azevém (Lolium multiflorum Lam.) and cornichão (Lotus corniculatus L.) due to their nutritional benefits, good palatability, regrowth, and hardiness. Considering the high degree of polyphagia of H. armigera and S. frugiperda, and the impact of maintaining continuous feeding areas (green bridges) in the management of these species, this work aimed to evaluate the development of H. armigera and S. frugiperda fed leaves of azevém and cornichão under laboratory conditions. The insects were collected in the city of Capão do Leão/RS in corn and soybean plantations. For each forage species, 130 newly hatched caterpillars were each placed in autoclaved glass tubes, with one-third of the tube length containing forage. The tubes were capped with waterproof cotton and placed in a climate-controlled room at 25 ± 1°C, 70 ± 10% relative humidity, and a 12-h photophase. The food was replenished daily until the caterpillars entered the pupae stage. The pupae were sexed and weighed, and the newly emerged adults were placed in pairs in PVC cages, lined with white A4 sulfite paper. The papers used as a laying substrate were removed and changed daily, and eggs were counted. The number of instars was determined by the linearized Dyar rule model. The complete randomization design was employed for the variables biological cycle length and viability of egg, caterpillar, pre-pupa, pupa, adult, and pre-oviposition phases and weight of caterpillars on the 14th day and pupae after 24 h. Based on the results obtained, a fertility life table was prepared. H. armigera did not complete the cycle, with only three instars and a duration of 22.1 and 24.6 days in azevém and cornichão, respectively. When evaluated in S. frugiperda caterpillars, development in forage species was observed, with five and six instars and duration of 51.7 and 45.1 days in azevém and cornichão, respectively. The azevém was distinguished by interference in the development cycle of the species, reducing the effect of the green bridge. In addition, surviving insects were susceptible to the effects of the agroecosystem due to the low-quality food source.

Biology and Life Stages of Pine Spittle Bug Ocoaxo assimilis Walker (Hemiptera: Cercopidae)

The first records of outbreaks of the Pine Spittle bug Ocoaxo assimilis Walker were recently identified from Puebla, Mexico, which promoted more than 2600 ha of forest foliar fall. Beyond the taxonomic and distribution information of this species, the basic traits of its biology remain unknown. This study aims to describe some biological aspects of O. assimilis, in a natural pine forest at Nicolás Bravo, Puebla (NB). Using morphological characteristics and a phylogenetic analysis of a fragment of cytochrome oxidase subunit I mtDNA (COI), immature instars with adults were studied; the instar number was determined by means of a multivariate analysis of 19 morphological characteristics of 121 specimens. The systematic sampling to evaluate the occurrence of nymphal specimens during a year, plus host selection experiments, allowed for determination of the abundance over time, voltism, and host preferences. Phylogenetic analysis of the COI supported that both nymphs and adults collected in NB correspond to O. assimilis. Principal coordinate analysis supported the existence of five nymphal stages. Field sampling and host selection experiments indicated that this species displays a single generation per year, is associated with the rainy season, and that specimens from the three first nymphal stages feed on roots of eight host species (one grass, four herbaceous species, one bush, and two trees). From the fourth instar, the insects feed on pine roots to complete their development, and when they are adults, they migrate to needles of young or mature pine stands of Pinus pseudostrobus to feed and reproduce.

Host Plant and Thermal Stress Induce Supernumerary Instars in Caterpillars.

Environmental stressors may induce variation in the number of larval instars of holometabolous insects. Host plant quality and ambient temperature can both induce this life history shift in the silver-spotted skipper, Epargyreus clarus (Cramer 1775) (Lepidoptera: Hesperiidae). To better understand this phenomenon, we raised larvae on high-quality (kudzu) or low-quality (wisteria) host plants in growth chambers under three temperature regimes (20, 26, and 32°C) that were either constant or diurnally fluctuating (T ± 5°C), and recorded survival and incidence of supernumerary instars. Larvae feeding on the low-quality host and/or experiencing thermal stress were more likely to show supernumerary development (SD). A subset of treatments yielded a mix of SD and TD (typical development) individuals, allowing for comparisons between phenotypes. Under the most stressful treatment (20 ± 5°C, wisteria), development time was 9 days longer in SD than in TD individuals; by contrast, at typical summer temperatures (26 ± 5°C), also on wisteria, total development time did not differ between these two phenotypes. Head capsules of both second and third instars were smaller in SD individuals. A retrospective logistic regression analysis indicated that third-instar head capsule size could be used to predict expression of the SD phenotype. By the ultimate instar, however, there were no detectable differences in head capsule size, and SD and TD individuals did not differ in pupal mass, strongly suggesting that the SD phenotype functions as a compensatory mechanism allowing E. clarus larvae to achieve the same size at metamorphosis (a strong fitness correlate) as TD larvae.

The life cycle of the Atlantic Beach-Cricket, Pseudomogoplistes vicentae Gorochov, 1996

The Atlantic Beach-Cricket, Pseudomogoplistes vicentae, inhabits shingle beaches, with a range that extends from the UK to the Canary Islands. Little is known about the natural history of this species, which is listed by the IUCN as Vulnerable. In the present study, a combination of field sampling (by pitfall trapping and direct searching) in spring, summer, autumn and late winter at two different sites in the UK, together with culturing eggs and nymphs in captivity, was used to determine the life cycle. Eggs laid in August in captivity showed no visible embryonic development until May and hatched the following July. There was no difference in the time taken to hatch between eggs maintained over winter at either 4 or 11 °C. Nymphal instars present in the field indicated that the majority of eggs hatch from June to early August. From October to February in the field, the majority of nymphs were estimated to be at the 7th instar. Development appeared to resume by April and nymphs reached adulthood by July to August in the field, two years after the eggs from which they hatched were likely to have been laid. The number of nymphal instars ranged from 10 to 11 (mode: 11) in males and 11 to 13 (mode: 12) in females. In captivity, most adult males died by the end of November, while 35% of females survived until March. Females preferred to oviposit in driftwood rather than in sand in the laboratory. This fact, together with the early embryonic diapause, suggests that the species might be able to disperse by rafting at the egg stage.