Pronotum Length Research Articles

A new species of Sulcana (Hemiptera: Cicadellidae: Gyponini) from the Brazilian Atlantic Forest

Sulcana cunicula sp. nov. is described and illustrated based on four specimens from municipality of Sao Jose dos Pinhais, state of Parana, Brazil. This species can be distinguished from others in the genus by the following characters: (1) head produced, slightly shorter than median length of pronotum; (2) aedeagus bearing a pair of acute ventral processes at mid-length of shaft and extended dorsally. A new record to Sulcana brevis DeLong & Freytag and a key to the three species of the genus are also presented.

Environmentally driven variability in size-selective females’ mating frequency of bush-cricket Pholidoptera griseoaptera

Reproduction in less favourable conditions requires genetic adaptation and/or behavioural plasticity of the organism. In order to determine the effects of these mechanisms on environment-associated variability in polyandry, a phenomenon related to reproductive success, we explored the frequency of copulations in females of nuptial gift-giving bush-cricket Pholidoptera griseoaptera (Orthoptera: Tettigoniidae) using a laboratory experiment. In a factorial design, we reared two populations originating from contrasting altitudes in two temperature treatment conditions. After 3 weeks for possible copulations in established mating groups, females (n = 108) contained between 0 and 15 spermatodoses (a proxy for the number of copulations) in their spermatheca. The mean number of spermatodoses per female did not differ either between lowland and highland populations or between warm and cold treatments. Thus, we did not observe main effects of these two factors on adaptation or plasticity. In contrast, the frequency of copulations was significantly affected by female size as log(number of spermatodoses) increased by 0.41 ± 0.27 per each 0.1 mm of pronotum length. However, interactions between the body size (the trait that predicts females’ quality for reproduction) with environmental factors revealed that larger females originating from the highland population and larger females reared in cold treatment copulated more often than smaller ones, whereas females’ size did not affect copulation frequency in the lowland population or in warm treatment. It suggests stronger competition among females in harsher environmental conditions, whereas effect sizes of interaction terms showed that observed mating behaviour expressed a similar extent of genetic and plastic responses to female size. This first observation of environment-associated body size-dependent mating behaviour suggests the interplay of sexual and natural selection in a nuptial gift-giving species.

Darwinian balancing selection: predation counters sexual selection in a wild insect.

The potential viability costs of sexually selected traits are central to hypotheses about the evolution of exaggerated traits. Estimates of these costs in nature can come from selection analyses using multiple components of fitness during the same time frame. For a population of tree crickets (Oecanthus nigricornis: Gryllidae), we analyzed viability and sexual selection on male traits by comparing Oecanthus prey of a solitary wasp to those that survived, and comparing mating individuals to solitary males. We measured forewing width (sexually size dimorphic and used for singing), head width, pronotum length, and size of hind jumping legs as potential targets of selection. Supporting the hypothesis that sexually selected traits have viability costs, we found that significant directional sexual selection for wider heads was opposed by significant viability selection for narrower heads. Nonlinear selection revealed that individuals with wide heads and small legs were most attractive, but individuals with narrow heads, large legs, and intermediate pronotum length were most likely to survive. Successful mating may put males at greater risk of predation, especially if copulation per se is risky. Such balancing selection in tree crickets may have constrained the evolution of sexual dimorphism in head size-a condition seen in other gryllids and orthopterans.

Evaluating indices of body condition in two cricket species.

Body mass components (dry mass, lean dry mass, water mass, fat mass) in each sex correlate strongly with body mass and pronotum length in Gryllus texensis and Acheta domesticus. Ordinary least squares (OLS) regression underestimates the scaling relationship between body mass and structural size (i.e., pronotum length) in both cricket species compared with standard major axis (SMA) regression. Standardized mass components correlate more strongly with scaled mass index () than with residual body mass (R i). R i represents the residuals from an OLS regression of log body mass against log pronotum length. Neither condition index predicts energy stores (i.e., fat content) in G. texensis. R i is not correlated with energy stores in A. domesticus whereas is negatively correlated. A comparison of condition index methods using published data showed that neither sex nor diet quality affected body condition at adulthood in G. texensis when using the scaled mass index. However, the residual index suggested that sex had a significant effect on body condition. Further, analysis of covariance (ANCOVA) suggested that diet quality significantly affects body mass while statistically controlling for body size (i.e., body condition). We conclude that the statistical assumptions of condition index methods must be met prior to use and urge caution when using methods that are based on least squares in the y -plane (i.e., residual index ANCOVA).

Attempt to define morphological parameters enabling sex determination of Ips typographus (Linaeus, 1758) (Coleoptera: Curculionidae: Scolytinae) using PCA and CLU

There are only two known methods for determining the sex of Ips typographus (L.) – dissection that can­not be used with live beetles and by distinguishing between the density of the hairs on the head, a less reliable method that requires experienced personnel. As a result, we have sought to find a more reliable method of sex determination for I. typographus which can be used with live specimens but is still reliable and easy to conduct. The aim of the article is to explore the inner structure in data from measurements of morphological parameters of spruce bark beetles and to find correlations which could be used for sex determination. The number of beetles in our sample was 110, all from the first trapping of one pheromone trap. The statistical methods of principal components analysis (PCA) and cluster analysis (CLU) were used to support any correlation between the sex parameter and other morphological parameters (weight, elytra length, elytra width, pronotum length, pronotum width). As no correlation was found in the case of sex, we can claim that it is not possible to determine sex according to the examined morphological parameters. However, we have found an interesting inner structure in the data and it was confirmed that even weight is slightly correlated with other morphological parameters.  

Estimation of dry mass of caddisflies Phylloicus elektoros (Trichoptera: Calamoceratidae) in a Central Amazon stream

Aquatic invertebrate biomass estimations are often important in ecological and biological studies. Biomass may be determined by regression models between body and case dimensions and dry mass. Using linear, exponential and power regressions we analyzed the relationship between body and case dimensions and the biomass of Phylloicus elektoros Prather, 2003. Furthermore, we used cross-validation to evaluate the predictions of our models and of the models developed for Phylloicus sp. from southeastern Brazil. We measured four body dimensions (head capsule width, interocular distance, body and pronotum length) of 152 larvae and two case dimensions (width and length) of 45 cases. Case width provided better fit with biomass than case length in all model classes. Body length provided the best biomass prediction. Biomass predictions using models proposed in the literature were 75% lower than the observed values. The power model provided the best fit between body and case dimensions with biomass. However, exponential models also provided good biomass estimates. We observed a close fit between body and case dimensions and biomass, but the predictive power of the models was low (~40%). The predictive power of models proposed in the literature was much worse than those built from local data and thus we do not recommend their use to predict the biomass of organisms from different regions.

Developmental Patterns inStagmomantis limbata(Mantodea: Mantidae): Variation in Instar Number, Growth, and Body Size

Development affects many components of life history and fitness, including body size. The present study examined the influence of developmental pattern, specifically the number of nymphal instars, on body size (pronotum length) in the praying mantid Stagmomantis limbata Hahn. Mantids were reared in the laboratory from hatching, on standardized diet, to examine variation in instar number. These lab data were then used to assess developmental patterns forfield-collected female nymphs. Laboratoryreared males and females varied in number of instars. Most females required 6 nymphal instars to reach adulthood (64%), whereas 36% underwent 7 instars. Seven-instar females reached the 4th, 5 th, and 6th instars faster than six-instar females, but had shorter pronota than the six-instar females at each of these stages. Seven-instar females were longer than six-instar females at adulthood. Interestingly, the total developmental period from hatching to adulthood was similar for lab-reared seven-instar and six-instar females. In the lab, most males (91%) underwent 6 instars, with the remaining 9% following a five-instar pattern. By the 4th instar, differences between the sexes began to appear. From the 4th instar onwards, females typically took less time than males to reach each instar. From the 5th instar onwards, females were longer than the males, and were longer as adults. Variation in developmental pattern (number of instars) was evident among siblings from the same ootheca; such intra-clutch variability in number of instars may be a bet-hedging strategy by ovipositing females in a variable environment. The laboratory data allowed for the detection of six-instar and seven-instar patterns among the field-collected females. The field-collected data suggest that females undergoing 6 nymphal instars reach adulthood later in the season, and at smaller body size, than seven-instar females.

Consequences of Intraspecific Variation in Female Body Size inStagmomantis limbata(Mantodea: Mantidae): Feeding Ecology, Male Attraction, and Egg Production

Body size is an important feature of organisms, influencing many components of life history and fitness, such as feeding success and reproductive output. Body size is considered especially salient for solitary predators, whose food intake hinges on individual predation success, which in turn is often driven by the relative sizes of predator and prey. The current study examined intraspecific variation in adult female length and its fitness consequences in a solitary predator, the praying mantid Stagmomantis limbata Hahn. Through a 5-yr integration of observational and experimental work in the field and captivity, we investigated the relationship between female pronotum length and prey size, diet breadth, male attraction, and measures of egg production (fecundity and ootheca mass). We found that longer females ate longer prey in the field and showed greater breadth of prey size than shorter females. Longer females did not necessarily feed at higher rates in the field, as measured by the rate of abdominal expansion. Female length failed to show significant effects on male attraction or on the incidence of cannibalism. Longer females had higher fecundity (mature eggs in body at death) and laid heavier oothecae than shorter females. In nature, longer females consistently emerged as adults earlier in the season than shorter females. Shorter female adults emerged when feeding rates were higher in the field, suggesting an incidental ecological benefit of shorter adult size.

Female Bush-Crickets, Pholidoptera griseoaptera, that have Received Smaller Ejaculates Show a Higher Mating Rate in the Field

Females of numerous insect species are known to be polyandrous, but there have been relatively few studies of factors associated with the degree of polyandry in females in the field. Number of copulations by females is negatively associated with ejaculate size across bush-cricket species. Assessing intraspecific variability is important when looking for and interpreting trait evolution. Therefore the aim of this study was to test the association between ejaculate size (i.e. volume of spermatodose-spermatophore- like structure formed within the spermatheca) and mating rate (i.e. number of spermatodoses) of females of Pholidoptera griseoaptera, while accounting for female body size (pronotum length) and age (number of hind leg's cuticular bands). The results based on field-caught individuals suggested that there were statistically significant nega- tive association between smallest and mean spermatodose volume, respectively, and number of copulations in this nuptial gift-giving bush-cricket species. This is in accor- dance with interspecific associations between ejaculate size and polyandry. However, lower slope of the intraspecific relationship may suggest lower importance of the ejaculate size in explaining females' mating rate variability in this nuptial gift-giving species.

Dietary choices and their implication for survival and development of omnivorous mole crickets (Orthoptera: Gryllotalpidae)

Omnivory is a common feeding strategy in terrestrial arthropods, and omnivores that partake of a mixed diet often gain developmental and reproductive advantages. We determined the palatability and preference of plant and animal foods for two omnivorous mole crickets, Scapteriscus vicinus Scudder and Scapteriscus borellii Giglio-Tos. Adults of both species fed more readily on carrots than bermudagrass blades, rhizomes, and roots. When given a choice, S. vicinus preferentially fed on carrots (plant diet) whereas S. borellii preferred mealworms (animal diet). Nymphs of both species were reared on animal, plant, or mixed (plant–animal rotation) diets. S. borellii fed mealworms developed faster, with greater body mass and survival, and a longer pronotal length compared to individuals fed only carrots. Nymphs of S. vicinus, however, performed slightly better when fed mealworms, and poorer when given a mixed diet. Omnivory among Scapteriscus mole crickets may be a beneficial adaptation for insects in low nitrogen, grassland environments. This work suggests that these two species respond differently to plant and animal diets. S. borellii has a survival and developmental advantage by ingesting animal tissue. Diet will influence the age distribution of field populations, and this may influence interactions with their grass host and natural enemies.

Morphometric Analysis ofOryctes rhinoceros(L.) (Coleoptera: Scarabaeidae) from Oil Palm Plantations

Morphometric analysis was performed on the oil palm pest Oryctes rhinoceros (L.) as part of a study to determine the possibility of a cryptic species complex occurring in this organism. Six beetle populations, each with a sample of 30 individuals, were examined. The morphometric variables measured were total body length, elytral length, pronotal length, pronotal width, and length of the cephalic horn. Principal component analysis and canonical discriminant analysis indicated no distinct discontinuity or clustering of populations. The morphology of individuals from different populations was observed to overlap on one another. These results indicate that O. rhinoceros show stability in morphometric character variance across a wide geographical range.

Instar Determination of Blaptica dubia (Blattodea: Blaberidae) using Gaussian Mixture Models

Abstract Instar determination is fundamental to both basic entomological research and its application. The cockroach, Blaptica dubia Serville (Blattodea: Blaberidae), is a popular pet and an excellent feeder insect for many reptiles and amphibians. A new method using Gaussian mixture models to determine the number of instars in this species is developed. Application of the method is illustrated by analysis of data collected on B. dubia. The analysis indicates that there are seven instars in B. dubia and that the growth ratio follows the Brooks—Dyar rule. The growth ratio of pronotal length, pronotal width, and head width are 1.26, 1.24, and 1.19, respectively. Because B. dubia shares a similar growth pattern with other paurometabolous insects, this method may be applicable to other species as well.

Morphometrics of the final instar exuviae of five cicada species occurring in urban areas of central Korea

Cicadas produce loud calling songs for mate attraction that can be a nuisance to city dwellers in Korea. Exuviae of final instars can be used to estimate population density. We investigated the morphological characteristics of final instar exuviae for five cicada species that are abundant in central Korea: Cryptotympana atrata, Hyalessa fuscata, Graptopsaltria nigrofuscata, Meimuna opalifera, and Meimuna mongolica. The characters analyzed were pro-mesonotum length, pronotum width, pronotum length, head width, abdominal circumference, body length, wing length, and femoral tooth angle. The results of a general linear model showed that species and sex were significant for morphological characters, and the result of post hoc analyses revealed that the mean values of most of the morphological characters measured were significantly different among the five cicada species. Three groups, Cryptotympana atrata, H. fuscata/G. nigrofuscata, and M. opalifera/M. mongolica, were distinctively identified based on most morphological characters. The distributions of femoral tooth angles did not overlap between H. fuscata and G. nigrofuscata, and the distributions of abdominal circumference did not overlap between M. opalifera and M. mongolica. Thus, the exuviae of all five cicada species could be easily distinguished based on morphological characters. We also provide a morphological key for the exuviae of all five cicada species in Korea.

Density‐dependent polyphenism and geographic variation in size among two populations of lubber grasshoppers (Romalea microptera)

Abstract.1. Density‐dependent phase polyphenism occurs when changes in density during the juvenile stages result in a developmental shift from one phenotype to another. Density‐dependent phase polyphenism is common among locusts (Orthoptera: Acrididae).2. Previously, we demonstrated a longitudinal geographic cline in adult body size (western populations = small adults; eastern populations = large adults) in the eastern lubber grasshopper (Romalea microptera) in south Florida. As lubbers are confamilial with locusts, we hypothesised that the longitudinal size cline was partly due to density‐dependent phase polyphenism.3. We tested the effect of density, population, and density×population interaction on life‐history traits (pronotum length, mass, cumulative development time, growth rate) of, and proportion surviving to, each of the five instars and the adult stage in a 2 × 3 factorial laboratory experiment with two lubber populations, each reared from hatchling to adult at three different densities.4. The effect of density on life history and survival was independent of the effects of population on life history and survival. Higher densities led to larger adult sizes (pronotum, mass) and lower survivorship. The western population had smaller adult masses, fewer cumulative days to the adult stage, and higher survivorship than the eastern population.5. Our data suggest that lubber grasshoppers exhibit density‐dependent phase polyphenism initiated by the physical presence of conspecifics. However, the plastic response of adult size to density observed in the laboratory is not consistent with the relationship between phenotypes and adult density in the field. Genetic differences between populations observed in the laboratory could contribute to size and life‐history differences among lubber populations in the field.

Male Weaponry in a Fighting Cricket

Sexually selected male weaponry is widespread in nature. Despite being model systems for the study of male aggression in Western science and for cricket fights in Chinese culture, field crickets (Orthoptera, Gryllidae, Gryllinae) are not known to possess sexually dimorphic weaponry. In a wild population of the fall field cricket, Gryllus pennsylvanicus, we report sexual dimorphism in head size as well as the size of mouthparts, both of which are used when aggressive contests between males escalate to physical combat. Male G. pennsylvanicus have larger heads, maxillae and mandibles than females when controlling for pronotum length. We conducted two experiments to test the hypothesis that relatively larger weaponry conveys an advantage to males in aggressive contests. Pairs of males were selected for differences in head size and consequently were different in the size of maxillae and mandibles. In the first experiment, males were closely matched for body size (pronotum length), and in the second, they were matched for body mass. Males with proportionately larger weaponry won more fights and increasing differences in weaponry size between males increased the fighting success of the male with the larger weaponry. This was particularly true when contests escalated to grappling, the most intense level of aggression. However, neither contest duration nor intensity was related to weaponry size as predicted by models of contest settlement. These results are the first evidence that the size of the head capsule and mouthparts are under positive selection via male-male competition in field crickets, and validate 800-year-old Chinese traditional knowledge.

Analysis of body size and fecundity in a grasshopper

We used linear regression, nonlinear regression and principal component analysis to examine the relationships among morphology, fecundity, and mating variables for lab-reared adult female Romalea microptera (Beauvois) (fam. Romaleidae) grasshoppers. Morphological variables included head width, pronotum length, femur length, adult eclosion mass, maximum mass reached before the 1st oviposition, and maximum mass reached before the 2nd oviposition. Fecundity (= reproductive) variables included clutch size Pod 1, clutch size Pod 2, total eggs Pods 1 2, mass Pod 1, mass Pod 2, time between adult eclosion and Pod 1, time between Pod 1 and Pod 2, and time between eclosion and Pod 2. Mating variables included number of matings and age of 1st mating. Most morphological variables were strongly positively correlated, and morphological variables (especially femur length, eclosion mass, and maximum body mass reached prior to oviposition) predicted many fecundity variables. Maximum body mass reached prior to laying Pod 1 was highly correlated with maximum body mass reached prior to laying Pod 2 (r =0 .93), and clutch size Pod 1 predicted clutch size Pod 2 (r = 0.72). However, time to oviposit (= interval between adult eclosion and oviposition) was generally unrelated to body size, body mass, or clutch size or mass. Hence, clutch size and pod mass are strongly determined by body size and mass at adult eclosion, but timing of oviposition is independent of body size and mass at eclosion. The results also suggest that early mating speeds oviposition, but that excessive mating reduces female fecundity, as measured by clutch size.

Rhynchophorus ferrugineus and Rhynchophorus palmarum

<i>Rhynchophorus ferrugineus </i>and<i> Rhynchophorus palmarum</i>

Laboratory Assessment of Altered Atmospheric Carbon Dioxide on Filamentous Green Algae Phenolic Content and Caddisfly Growth and Survival

ABSTRACT To test global change effects on lentic ecosystems, we examined I) if algae phenolic content was influenced by CO2 treatments, and 2) if algivores fed CO2-treated algae were impacted. Four common Chlorophytes (Cladophora glomerata, Spirogyra grevilleana, Ulothrix, fimbriata, and Zygnema sp.) were grown under three atmospheric carbon dioxide environments (200, 360, and 3000 mg/L). Algivore (the microcaddisfly Hydroptila waubesiana [Trichoptera: Hydroptilidae]) feeding assays, using identically treated algae (C. glomarata and U. fimbriata) as a food source, were run in parallel. Generally, Folin-Denis reactive phenolics were highest among algae grown under high CO2 treatments, intermediate at ambient CO2, and lowest under low CO2 treatment. Differential species responses in reactive phenolics were observed, with U. fimbriata being most responsive (∼6 %) to CO2 enrichment, and C. glomarata being unresponsive (<1%). Regardless of algal species or CO2 treatment, developmental rates of H. wauhesiana larvae to mid and late instars were statistically identical. Percent survival for larvae given U. fimbriata and C. glomerata were similar; however, survival rates were higher when larvae were fed low CO2 treated U. fimbriata. For larvae fed C. glomerata, the general trend was that larvae fed algae grown at high CO2 levels had the greatest head capsule width; those fed algae at low CO2 levels had the greatest head capsule length and pronotal length. In contrast, larvae fed U. fimbriata had the largest head capsule widths under ambient CO2 levels, the largest head capsule widths under high levels, and had equal pronotal lengths at all CO2 levels. Larvae fed C. glomerata grown under ambient conditions produced portable cases of the greatest length at the experiment's conclusion, but no distinct trend was seen for larvae fed U. fimbriata. Overall, CO2 induced production of reactive phenolics in chlorophytes did not appreciably influence herbivorous microcaddisfly development or survival.

Morphometric analysis of population samples of soldier caste of Odontotermes obesus (Rambur) (Isoptera, Termitidae, Macrotermitinae)

In order to study morphometric variations in Odontotermes obesus (Rambur), samples from nineteen nests were statistically analyzed for mean, standard deviation, standard error, coefficient of variability and confidence interval (95%) and analysis of variance (Model II ANOVA), The mean values of the different population samples were compared with the student t-test, following the Minitab version and Sokal &amp; Rohlf (1973). In the study of external characters, measurements form a very important component, particularly for identification of species. However, the reliability of the measurements depends on the extent of variability which the structures show within and between colonies. For each individual soldier, the following nine parameters were measured: i) length of head; ii) width of head at mandibles; iii) width of head at the posterolateral ends of antennal carinae; iv) maximum width of head; v) length of left mandible; vi) tooth of left mandible from tip; vii) length of pronotum; viii) width of pronotum; ix) length of postmentum; and x) width of postmentum.

Multiple Morphological Measurements as Larval Indicators for &lt;I&gt;Saperda vestita&lt;/I&gt; (Coleoptera: Cerambycidae)

Ten sclerotized morphological structures were measured to determine the number of instars of the linden borer, Saperda vestita Say (Coleoptera: Cerambycidae). Linear regression analysis revealed a significant relationship between maximal cranial width and the other structures measured, including length of the terminal labial palpomere, length of the first thoracic spiracle, width of the first thoracic spiracle, length of clypeolabral suture, length of frontoclypeal suture, cranial width measured at antennal insertions (from outside edges), maximal prothoracic width, mesal pronotal length, and length from apical margin of labrum to distal end of the prothorax. Linden borer instar number was determined through the use of frequency distribution diagrams. Mean, standard error of the mean, Dyar’s ratio, and Crosby’s ratio were calculated and evaluated for each instar designation to confirm that none of the five to six instars of S. vestita was overlooked.