Nymphal Development Time Research Articles

Effects of serine protease inhibitors on growth and development and digestive serine proteinases of the Sunn pest, Eurygaster integriceps.

In the current study the effects of serine proteinase inhibitors (TLCK, TPCK, SBTI, and a combination of SBTI and TPCK) with concentrations of 1% and 4% of dietary protein in artificial diets were tested against growth of the Sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae), development, and its gut serine proteinase targets. Analysis of variance indicated that protease inhibitors affected nymphal development time, adult weight, and survival. Mean development time of third instar nymphs in control, SBTI (1%), TLCK (1%), and TPCK was 7.18, 9.74, 9.97, and 8.52 days, respectively. The highest mortality (100 % mortality) was observed when a combination of TPCK and SBTI, both at 4% of dietary protein, was used followed by TPCK (4%) that produced 95% mortality. There were significant differences in proteinase activity between treatments and controls when BApNA and SAAPFpNA were used as substrates for trypsin and chymotrypsin, respectively. Reduction of trypsin activity in insects fed with low doses of SBTI (1%), TLCK (1%), and both doses of TPCK (1% and 4%) was 40, 26, 23, and 17%, respectively. Inhibition of chymotrypsin activity was seen in the insects fed on SBTI (1%), TLCK (1%), and TPCK (4%) where inhibition was 14, 9, and 36%, respectively. Maximum inhibition of chymotrypsin activity was observed in the insects fed on diets containing high doses of TPCK (4%). In gel assays, the greatest effects were observed when E. integriceps were fed on high doses of SBTI and TPCK. Therefore, TPCK followed by SBTI proved to be the most effective proteinase inhibitors of E. integriceps.

흑다리긴노린재[Paromius exiguus (Distant)] 온도발육 모형

흑다리긴노린재 [Paromius exiguus (Distant)]의 온도에 따른 발육 시험을 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, <TEX>$35{\pm}1^{\circ}C$</TEX>의 9개 항온, 광주기 14L:10D, 상대습도 20-30% 조건에서 수행하였다. 알은 <TEX>$15^{\circ}C$</TEX>에서 발육하지 못하였으며 <TEX>$17.5^{\circ}C$</TEX>에서 발육기간이 28.2일로 가장 길었고 온도가 증가함에 따라 짧아져 <TEX>$35^{\circ}C$</TEX>에서 5.9일이 소요되었다. 약층은 <TEX>$17.5^{\circ}C$</TEX>와 <TEX>$35^{\circ}C$</TEX>에서 1령 약층을 넘기지 못하고 모두 사망하였으나, <TEX>$20-32.5^{\circ}C$</TEX> 범위에서는 온도가 증가할수록 발육기간이 짧아지는 경향을 보였고, 4령을 제외한 모든 영기에서 <TEX>$32.5^{\circ}C$</TEX>에서의 발육기간이 <TEX>$30^{\circ}C$</TEX>와 같거나 더 길어져 발육속도가 둔화되는 경향을 보였다. 온도와 발육율과의 관계를 설명하기 위해 선형 및 3개의 비선형(Briere 1, Lactin 2, Logan 6) 모형을 사용하여 분석하였다. 선형모형을 이용하여 추정한 알과 전체 약층발육의 발육영점온도는 <TEX>$13.8^{\circ}C$</TEX>와 <TEX>$15.3^{\circ}C$</TEX>였으며 발육 유효적산온도는 각각 109.9, 312.5DD였다. 3가지 비선형 모형 종 Logan-6 모형이 모든 발육단계에서 온도와 발육율과의 관계를 가장 잘 설명하였다 (<TEX>$r^2$</TEX>=0.94-0.99). 알 및 유충의 발육단계별 발육완료 분포는 3-parameter Weibull 함수를 사용하였으며 모든 발육단계에서 높은 <TEX>$r^2$</TEX> (0.91-0.99) 값을 보여 양호한 모형 적합성을 보였다. The developmental time of immature stages of Paromius exiguus (Distant) was investigated at nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, <TEX>$35{\pm}1^{\circ}C$</TEX>), 20-30% RH, and a photoperiod of 14:10h (L:D). Eggs did not develop at <TEX>$15^{\circ}C$</TEX>, and their developmental time decreased with increasing temperatures. Its developmental time was longest at <TEX>$17.5^{\circ}C$</TEX> (28.2 days) and shortest at <TEX>$35^{\circ}C$</TEX> (5.9 days). The first nymphs failed to reach the next nymphal stage at 17.5 and <TEX>$35^{\circ}C$</TEX>. Nymphal developmental time decreased with increasing temperatures between <TEX>$20^{\circ}C$</TEX> and <TEX>$32.5^{\circ}C$</TEX>, and developmental rate was decreased at temperatures above <TEX>$30^{\circ}C$</TEX> in all stages except for the fourth nymphal stage. The relationship between developmental rate and temperature fit a linear model and three nonlinear models (Briere 1, Lactin 2, and Logan 6). The lower threshold temperature of egg and total nymphal stage was <TEX>$l3.8^{\circ}C$</TEX> and <TEX>$15.3^{\circ}C$</TEX>, respectively. The thermal constant required to reach complete egg and the total nymphal stage was 109.9 and 312.5DD, respectively. The Logan-6 model was best fitted (<TEX>$r^2$</TEX>=0.94-0.99), among three nonlinear models. The distribution of completion of each development stage was well described by the 3-parameter Weibull function (<TEX>$r^2$</TEX>=0.91-0.99).

Desarrollo post-embrionario, fecundidad y consumo de alimento de Dichroplus exilis (Orthoptera: Acrididae) bajo condiciones controladas

Dichroplus exilis is a widely distributed species in Southern South America. Although there have been reports of D. exilis as an agricultural pest, some recent observations suggest that the damage attributed to D. elongatus may actually have been caused by D. exilis. This study was conducted to determine the postembryonic life cycle stages, fertility and food consumption of this species under controlled conditions (30 degrees C, 14L-10D, 40% RH). Individuals employed belong to the laboratory-hatched first generation (F1), from adults (n = 64, female = 28, male = 36) collected in natural grasslands near Rafaela, Santa Fe province in North-Eastern Argentina. Three cohorts of 16, 17 and 20 individuals were monitored independently in acetate tubes on a daily basis, until death of the last insect. Average fecundity was 381.84, 38.54 eggs per female. Egg-pod incubation time was 14.4, 1.08 days and six nymphal instars were recorded. Nymphal development time was 41.38, 0.71 days (I = 8.73, 0.20; II = 6.38, 0.24; III = 5.64, 0.33; IV = 7.15; 0.43; V=9.76, 0.54; IV = 7.85, 0.95). The recorded food consumption was 9.89, 1.08 (mg/ind/day) for nymphs IV, 18.04, 0.73 (mg/ind/day) for nymphs V-IV, 16.76, 1.06 (mg/ind/day) for pre-reproductive males, 28.09, 1.81 (mg/ind/day) for pre-reproductive females, 7.71,0.91 (mg/ind/day) for reproductive males and 13.06, 0.71 (mg/ind/day) for reproductive females, while the average adult food consumption, regardless of sex and reproductive status, was 16.41, 4.32 mg/day. Average food consumption of adult females was 17.47, 1.15 mg, and was significantly higher than that of males (10.83, 0.91mg). Data obtained in this study showed that D. exilis exhibits at least some of the biological attributes needed to configure an actual or potential agricultural pest, albeit not yet recognized as such. Field monitoring of grasshopper communities in areas where damage by D. exilis is suspected is envisaged in order to determine its possible status as a pest.

The effects of different temperatures and relative humidity on the development, mortality and nymphal predation of Anthocoris minki

Mass rearing techniques are a necessity in developing a suitable and economic biological control method. Anthocoris minki Dohrn (Heteroptera: Anthocoridae), which is successfully reared for use in biological control, is a promising indigenous Anthocoris species for biological control of Agonoscena pistaciae Burckhardt and Lauterer (Homoptera: Psyllidae) in pistachio orchards. Development time of nymphal instars, mortality percentage and prey consumption of A. minki fed on Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs were studied at three constant temperatures (20, 25 and 30 ± 1°C) and two relative humidity levels (40 and 65 ± 5%) under laboratory conditions. Temperature and r.h. significantly affected development time and nymphal prey consumption of A. minki. Duration of incubation and total nymphal development time decreased significantly with each increase in temperature. Total nymphal development time of A. minki at 40% and 65% r.h. was 18.6 and 18.6 days at 20°C; 13.7 and 14.6 days at 25°C; and 10.8 and 11.8 days at 30°C, respectively. The shortest nymphal development time and highest nymphal mortality percentage were recorded at 30°C and 40% r.h. The lowest nymphal mortality was 30.1% and 32.1% at 40% and 65% r.h., respectively, at 25°C; the highest nymphal mortality was 51.5% and 52.1% at 20° and 30°C, respectively, and 40% r.h. The highest average number of E. kuehniella eggs consumed was 123.1 at 20°C and 65% r.h., and the lowest was 86.4 at 30°C and 40% r.h. during nymphal development time of A. minki.

New soybean variety, Agakong, as a host of Riptortus pedestris (Fabricius): Study on field occurrence and biological attributes in the laboratory

A new variety of soybean, Agakong, has good nutritious values, thus is expected to be grown widely in the near future. To evaluate Agakong as a new soybean host of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae), we assessed the biological attributes of the stink bug fed on Agakong and its field (Fabricius) occurrence in comparison with other varieties, Cheongjakong and Daewonkong. In laboratory studies, the nymphal development time and fecundity of R. pedestris was unaffected by the soybean varieties. However, nymphal mortality of R. pedestris fed on Agakong was significantly lower than those fed on Daewonkong. Furthermore, adult females become significantly larger when they fed on Agakong. R. pedestris preferred Cheongjakong seeds to Daewonkong or Agakong seeds in Petri dish choice experiments. The population dynamics of eggs, nymphs, and adults on the three soybean varieties planted in a 3 × 3 Latin square design were assessed by direct counting from 13 July to 22 September, 2007 at 10 days intervals. R. pedestris was the most abundant stink bug species on all the tested soybean varieties. The occurrence of R. pedestris eggs and nymphs was not significantly different among the three varieties. However, the seasonal density of R. pedestris adults was lower on Agakong than on Cheongjakong. Although higher R. pedestris populations were not observed in the field, the possibility of R. pedestris becoming a pest on this newly developed soybean variety can't be ruled out since some of its biological attributes were positively affected by feeding on Agakong seeds.

Wheat Antixenosis, Antibiosis, and Tolerance to Infestation by &lt;I&gt;Delphacodes kuscheli&lt;/I&gt; (Hemiptera: Delphacidae), a Vector of “Mal de Río Cuarto” in Argentina

"Mal de Rio Cuarto", is the most important virus disease of corn, Zea mays L., in Argentina. It is caused by the Mal de Rio Cuarto virus (family Reoviridae, genus Fijivirus. MRCV), which is a persistent virus transmitted by Delphacodes kuscheli (Fennah 1955) (Hemiptera: Delphacidae). Because corn is not a natural host of D. kuscheli, it has little protection from this pest. In contrast, wheat, Triticum aestivum L., is one of the main hosts of this vector and a reservoir of MRCV. The aim of this work was to identify genes involved in antixenosis, antibiosis, and tolerance of infestation by D. kuscheli in wheat, which might be used to reduce the population level of this vector on corn. A set of recombinant dihaploid (RDH) lines for chromosome 6A derived from the F1 cross between 'Chinese Spring' (CS) X 'Chinese Spring (Synthetic 6A)' (S6A) substitution line, was used for mapping. The S6A parental line is resistant to the MRCV vector. Antixenosis, antibiosis, and tolerance were evaluated using conventional tests in controlled environmental conditions. Most of the RDH and S6A showed higher levels of antixenosis against D. kuscheli than the parental line CS. The RDH lines showed highly significant antibiosis in terms of the duration of first, third, and fifth nymphal instars, developmental time (days), survival and fecundity. There were highly significant differences in the tolerance to D. kuscheli based on the chlorophyll content of the first and second leaves, foliar area, and aboveground fresh and dry weights. The duration of the fifth nymphal instar and the developmental period were significantly associated with Xgwm1017 marker loci, located at 48 cM on 6AL. Another quantitative trait locus accounting for the variation in chlorophyll content of the first leaf was associated with the interval between loci Xgwm459 and Xgwm334a, located in the telomeric region of the 6AS chromosome arm. The alleles with positive effects came from S6A. Antibiotic resistance of RDH could be useful for controlling the population increase of the MRCV vector on wheat, because prolonging the duration of development increases the period between two subsequent generations, so reducing the abundance of infective populations colonizing corn.

Role of symbiotic gut bacteria in the development ofAcrosternum hilareandMurgantia histrionica

AbstractThe green stink bug,Acrosternum hilare(Say), and the harlequin bug,Murgantia histrionica(Hahn) (both Heteroptera: Pentatomidae), are pests of many economically important crops. Although both species have been studied extensively, until recently their relationships with symbiotic gut bacteria have remained unknown. The endosymbionts may be important, as other pentatomomorphan species harbor vertically transmitted gut bacteria that play an important role in the biology of their host insects. We report the role of gut symbiotic bacteria on the development and fitness ofA. hilareandM. histrionicaby comparing control insects with individuals that hatched from surface sterilized egg masses. We studied the life history ofA. hilareandM. histrionicaunder laboratory conditions at 23 ± 2 °C and L16:D8, measuring nymphal mortality and development time, and estimating other demographic parameters. We also evaluated egg masses, nymphs, and adults of both species with diagnostic PCR primers for the presence of specific gut symbiotic bacteria for both treatments. Our results show that egg mass surface sterilization eliminates or reduces the prevalence of this bacterium‐insect symbiosis in both species.Acrosternum hilare’s development time, survivorship, and other demographic parameters were negatively affected by surface sterilization of egg masses. Conversely,M. histrionica’s survivorship was marginally increased by clearing its symbiont infection during the first generation; however, mean generation time was significantly longer. Our data indicate that the degree of mutualism in this association for pentatomid species is variable, given thatA. hilarerequires its symbiont for adequate development and survival, whereasM. histrionica’s symbiont may not be required for development and survival under the experimental conditions used.

Impact of certain corn cultivars on some ological parameters of Rhopalosiphum maidis (Fitch) tera: Aphididae)

The development, survival rate, reproduction and biological parameters of the corn leaf aphid, Rhopalosiphum maidis (Fitch), on five corn cultivars were evaluated at 25°C under laboratory conditions. The corn leaf aphid had a longer nymphal developmental time of 4.99, 4.98, 4.73, 4.46, and 5.60 day of Ada9516, K. Arifiye, PrimerG626, Pegaso and TTM815, respectively. The corn leaf aphid reared on K. Arifiye had the highest fecundity (69.65 offspring/aphid). The lower percentage survival rates were observed on TTM815 than that of the others. Net reproductive rate (Ro) was lowest (67.35 offspring/aphid/generation) on TTM815. The intrinsic rate of increase (rm) was lower on TTM815 than that of the other corn cultivars. TTM815 showed resistance to the pest.

Nymph and adult biology of Dichelops melacanthus (Dallas) (Heteroptera: Pentatomidae) feeding on cultivated and non-cultivated host plants

The biology of the pentatomid Dichelops melacanthus (Dallas) feeding on cultivated and non-cultivated plants was studied in the laboratory. Nymph mortality varied from approximately 60 on corn (seed mature) to 77% on wheat (ear immature); no nymphs survived on seedlings of corn or wheat. Nymph developmental time on soybean, corn or wheat (seed, pod or ear) varied from 25.5 to 32.8 days. Body weight at adult emergence was similar and greater on most foods than on wheat ear. Nymphs fed preferentially on soybean (pod immature). On non-cultivated hosts, nymphs showed high mortality (73%) on crotalaria (pod immature); on tropical spiderwort (stem) all nymphs died. Nymphs took longer time to develop on crotalaria and/or on spiderwort than on soybean. Body weight at adult emergence did not differ on crotalaria or soybean. Survivorship decreased with time on most foods, with approximately 50% of adults alive at day 30. On corn and wheat seedlings approximately 80% of adults were dead on day 20. Adult longevity ranged 31-43 days, except on corn and wheat seedlings < 15 days. Females % ovipositing peaked ( approximately 76%) on soybean (pod or seed immature), and was minimum ( approximately 9%) on wheat ear (immature); no females reproduced on seedlings of corn or wheat. Preoviposition period was shorter ( approximately 12 days) on soybean (immature pod or seed) and longer ( approximately 37 days) on wheat (ear immature). Fecundity was similar and higher on all foods than on wheat (ear immature). Body weigh gain occurred on all foods, but on corn and wheat seedlings. Adults fed preferably on soybean (pod immature and seed mature); wheat (seedling) was the least preferred food.

Nymph developmental time and survivorship, adult longevity, reproduction and body weight of Dichelops melacanthus (Dallas) feeding on natural and artificial diets

The biology of nymphs and adults of the neotropical pentatomid, Dichelops melacanthus (Dallas), feeding on the natural foods, soybean, Glycine max (L.) Merrill immature pods, and corn, Zea mays L. immature seeds, and on an artificial dry diet, was studied in the laboratory. Nymph developmental time was shorter on the natural foods (ca. 21-22 days) than on the artificial diet (28 days), and most nymphs reached adulthood on the food plants (55% on soybean and 73% on corn) than on the artificial diet (40%). Fresh body weight at adult emergence was similar and higher for females raised as nymphs on the natural foods, compared to females from nymphs raised on the artificial diet; for males, weights were similar on all foods. Mean (female and male) survivorship up to day 20, decreased from 55% on soybean to 40% on corn, down to 0% on the artificial diet. Total longevity for females was higher on soybean, while for males was similar on all foods. About three times more females oviposited on soybean than on corn, but fecundity/female was similar on both foods. On the artificial diet, only one out of 30 females oviposited. Fresh body weight of adults increased significantly during the first week of adult life, and at the end of the 3rd week, weight gain was similar on all foods.

Mechanisms of resistance in cotton to whitefly Bemisia tabaci (Homoptera: Aleyrodidae): antibiosis

The antibiotic effects of 12 different cotton genotypes on Bemisia tabaci (Gennadius) were studied during June–July and August–September 2003, with the objective to determine the biological parameters which are important to study the mechanism of antibiosis and to identify the genotypes in which antibiosis is operating. The detailed biology of whitefly, i.e. developmental period, survival, fecundity, longevity and sex ratio were studied under ‘no choice’ conditions, by confining the whiteflies in leaf cages. The study revealed that incubation period, nymphal developmental time, total developmental time, nymphal survival, total survival, fecundity and female longevity are the most important biological parameters for detecting the presence of antibiosis in resistant cotton genotypes against whiteflies. On the other hand, pupal period and survival, male longevity and sex ratio do not seem to play important roles in antibiosis. The combined effect of these parameters indicated that Gossypium arboreum genotype PA 183 was the most resistant while Bt 6304, TX Maroon 2–78 and F846 were the most susceptible ones. Other genotypes with moderate resistance include Supriya and LD 694.

Effects of the susceptibility of rice varieties to Sogatella furcifera on nymphal development and reproduction of Microvelia horvathi through a food chain

AbstractThe effects of four rice varieties highly susceptible (‘Xiang‐Zao‐Xian31’ and ‘Jia‐Yu164’), moderately susceptible (‘Wei‐You402’), and resistant (‘Zhu‐Liang‐You02’) to the whitebacked planthopper Sogatella furcifera on the nymphal development, reproduction and survival of Microvelia horoathi were investigated through a food chain using Sogatella furcifera as herbivore prey. Significant longer nymphal developmental time were observed in the 1st, 4th, 5th instar and whole nymphal stage of M. horvathi raised on S. furcifera fed ‘ZLY02’ and ‘WY402’ than those of the other two varieties. M. horvathi raised on S. furcifera fed resistant ‘ZLY02’ showed a significant lower survival of whole nymphal stage than those fed other three susceptible varieties. Moreover, M. horvathi raised on S. furcifera fed resistant ‘ZLY02’ had shorter female longevity and lower lifetime fecundity than those of on susceptible ‘XZX31’. Our results suggest that the S. furcifera‐resistant rice variety ‘ZLY02’ had a negative effect on the growth and development of the predator M. horvathi through a food chain.

Effect of Photoperiod on the Life History of the Predatory Bug, Macrolophus Caliginosus Wagner [Hemiptera:Miridae

Laboratory experiments were carried out to study the effect of photoperiod on the life history of the predator Macrolophus caliginosus Wagner [Hemiptera: Miridae] fed on eggs of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) [Homoptera: Aleyorodidae]. Day-length had no significant effect on either nymphal mortality, development time or adult longevity of M. caliginous. The absence of light had no negative effect on the consumption rate of M. caliginous. However, the number of T. vaporariorum eggs consumed by the predator increased with decreasing photoperiod. Light was of significance for the development of the predator embryos during incubation period as no hatching occurred under continuous darkness, but hatching was reduced at 8L:16D in comparison to hatching at 16L:8D.

The brine shrimp Artemia sp. as alternative prey for rearing the predatory bug Macrolophus caliginosus

Abstract The predatory bug Macrolophus caliginosus , which is widely used in greenhouse crops, is limited in its application by its high price. An important factor in the cost is the high price of Ephestia kuehniella eggs, the prey used in their mass rearing. In order to reduce their price, alternatives to moth eggs are currently being investigated. The brine shrimp Artemia sp. is produced in large quantities in saline lakes and is fed as live food source to the larvae of a variety of marine and freshwater organisms. In this study, we tested Artemia sp. as prey for rearing M. caliginosus from two strains. We evaluated developmental and reproduction parameters of the predator when fed nauplii, enriched nauplii with a fatty acid, dry cysts and hydrated cysts, and were compared with those obtained when the predator was fed with E. kuehniella eggs. Nauplii had a significant reduction in survivorship, a delay in development of nymphs and a low reproduction of adults. Nauplii enriched with docosahexaenoic acid (DHA, 22:6 n − 3), a common practice for larviculture of some marine fish species, resulted toxic to M. caliginosus nymphs and survival was quite low. On the contrary, either dry or hydrated cysts from the two strains tested of the brine shrimp produced the same nymphal survivorship, nymphal development time and weight and fecundity of adults as those obtained with E. kuehniella eggs. Demographic parameters of the eighth generation of the predator reared with cysts of the two strains, either dry or hydrated, were as good as those of moth eggs. We concluded that Artemia sp. cysts were a good substitution prey for the mass rearing of M. caliginosus .

Bacteria in the Gut of Southern Green Stink Bug (Heteroptera: Pentatomidae)

Laboratory studies with the southern green stink bug, Nezara viridula (L.), indicated the presence of bacteria Klebsiella pneumoniae (Schroeter) and Enterococcus faecalis (Andrewes & Horder) in the crop/stomach (ventriculus 1-3; V1-V3), and possibly Pantoea sp. in the gastric caeca (ventriculus 4; V4). Culturable bacteria were most abundant in V1-V3, and their abundance was drastically reduced in V4. The variable pH in the gut did not affect the presence of bacteria. Elimination of bacteria from the gut, by using the antibiotic kanamicin, did not affect nymphal developmental time or cause mortality, but it did cause reduced weight at adult emergence.

Population dynamics, growth and production of Sigara selecta (Fieber, 1848) (Hemiptera, Corixidae) in a Mediterranean hypersaline stream

Summary1. This is the first study on the life cycle, growth and production of Sigara selecta, a Palearctic corixid species typical of brackish and saline waters, at the warmest limit of its European distributional range. The study combines field and laboratory approaches.2. The S. selecta population studied was multivoltine, producing four asynchronous cohorts from early spring to December and overwintering in the adult state. Development time from egg to first adult ranged from 2 to 3 months. A minimum temperature threshold of 10 °C and diel amplitude of ≥10 °C were observed for reproduction and oviposition.3. Maximum density and biomass were reached in mid spring and early autumn. The sex ratio was unbalanced, females dominating during most of the year, except in spring, when the sex ratio was balanced or dominated by males during the first adult emergence.4. Laboratory rearing experiments at constant temperatures (18, 22 and 26 °C) pointed to a significant effect of temperature on egg development and nymphal growth. In the range of temperatures tested, both egg and nymphal instar duration decreased with increasing temperature. Mean nymphal development time varied from 43 days at 26 °C to 71 days at 18 °C, with a mean of 57 days. Survivorship was independent of temperature.5. A reduction in nymphal and adult length was observed with increasing temperature.6. Growth rates decreased with increasing body mass and increased as temperature increased. The first nymphal instar had the highest length increments and growth rates in all temperature treatments.7. Satisfactory agreement was found between the field and laboratory degree‐days required for complete development from egg to first adult. At constant and variable thermal regimes, degree‐days decreased with increasing temperature.8. Rate of growth in the field could be predicted with reasonable accuracy from a simple model obtained as a function of body mass. The model explained 67% of the variability in growth rates.9. Annual production and production/biomass ratio (P/B) of S. selecta estimated by the Instantaneous Growth method were 1.28 g m−2 year−1 and 13.71, respectively. Spring and autumn cohorts contributed 32% and 54%, respectively, of total annual production. Maximum production corresponded to intermediate temperature periods, although summer production may have been underestimated because of the longer sampling interval relative to cohort interval production. The Size Frequency method underestimated production by at least 18% with respect to the Instantaneous Growth method.

Secondary metabolite variation affects the oviposition preference but has little effect on the performance of Boreioglycaspis melaleucae: A biological control agent of Melaleuca quinquenervia

Variation in plant quality frequently impacts the biology of herbivorous insects. This variability can affect the outcome of biological control projects, especially during colonization of incipient populations and mass production. The invasive species Melaleuca quinquenervia is a weed of Florida that decreases biodiversity of natural areas. At least two chemical variants of M. quinquenervia occur in Florida, each differing in their foliar terpenoid profiles dominated by either viridiflorol or E-nerolidol. Biological control efforts against this weed resulted in the introduction of two insect species. The second agent released was a psyllid, Boreioglycaspis melaleucae. Described herein are results describing changes in the levels of secondary metabolites from plants of each chemotype when fertilized at three levels. Additionally, the results of psyllid feeding studies are presented describing the influence of these factors on the performance and oviposition choice. The results indicate that despite generally lower nitrogen content and increased secondary metabolite concentration in the viridiflorol chemotype, little change in psyllid biology was observed when fed leaves of this chemotype. Chemotype differences primarily influenced oviposition preference, where more than twice the number of eggs were laid on the viridiflorol chemotype. Nymphal development time was also delayed 0.7-day when fed leaves of the viridiflorol chemotype. Regardless of chemotype, nymphal survival increased, and development time decreased when fed leaves from the higher fertilizer level. The difference in susceptibility between the psyllid B. melaleucae and the weevil Oxyops vitiosa may be explained by differences in feeding behavior, whereby the psyllid feeds selectively inside leaves and avoids secondary metabolites stored in oil glands.

Plant quality, progeny sequence, and the sex ratio of the sycamore aphid, Drepanosiphum platanoidis

AbstractThe reproductive sequence of sexuparae of the sycamore aphid, Drepanosiphum platanoidis (Schrank) (Homoptera: Callaphididae), observed in the field and glasshouse was examined to elucidate the relationship between host nutrition and sex ratio. The observations were made in autumn when the transition from parthenogenetic to sexual reproduction occurred. A switch occurred in the reproductive sequence of the sexuparae. The production of apterous sexual females (oviparae) was followed by alate males, after a brief reproductive pause lasting 2.5–4.0 days. The switchover period was relatively constant across treatments and years. On poor hosts, the first appearance of the oviparae was a day later, whereas the first appearance of males was a day earlier than those on good nutrition. The primary sex ratio (i.e., proportion of males) was numerically female biased. Under semi‐natural field conditions it was 0.22, but altered to 0.18 and 0.29, respectively, under poor and good host nutrition in the glasshouse. In both the field and glasshouse, nymphal development time was significantly longer in oviparae (ca. 22 days) than in males (ca. 18 days). The time from birth to adult was significantly shorter on good hosts (oviparae: 20 days; males: 17 days) than on poor hosts (oviparae: 23 days; males: 19 days). The proportion of nymphs surviving to the adult moult was not dependent on sex in both the field and glasshouse, but the chances of survival were slightly enhanced under good (88%) compared with poor (82%) host nutritive status. In conclusion, the order of morph production and differences in maturation times ensured the synchronisation of the sexes so that mating and oviposition opportunities were optimised before the onset of winter. The female‐bias in the sex ratio maximised the fitness of sexuparae, and reduced the chances of local mate competition by economising in members of the competing sex.

Carcass analysis to improve a meat-based diet for the artificial rearing of the predatory mirid bugDicyphus tamaninii

Improvement of an existing meat-based diet has been obtained for rearing the generalist predator Dicyphus tamaninii (Heteroptera: Miridae). The approach followed, different from the classical addition/deletion method, was performing biochemical analysis of adult carcasses in order to have information about the nutritional status of the predator. Comparison of total, free amino acids and lipid composition of meat-reared and conventionally reared females allowed detecting some nutritional deficiencies. A reformulated diet with new sources of proteins and lipids was tested again with the predator. Some biological parameters of bugs that were inferior in the initial meat diet when compared with those of the conventionally reared insects, such as nymphal development time and fresh weight, have been improved with the reformulated diet.

The effect of past condition on a multicomponent sexual signal.

Sexual-selection theory predicts that multiple signals may reveal male condition at different stages of life, thus allowing females to make a more reliable assessment of male quality. While the effect of current condition on signal design is well established, few studies have experimentally investigated the effects of past condition. We therefore manipulated the nutritional condition of male nymph field crickets Gryllus campestris and assessed the enduring effects on multiple components of the adult calling song. Food-restricted males had longer nymphal development times and smaller adult body sizes than nymphs with ad libitum food access. Nymphal feeding conditions specifically affected the allometric relationship between body size and harp size, as food-restricted males developed comparatively small harps, leading to a calling song of higher carrier frequency than that produced by similar-sized control males. Other calling-song components, notably chirp rate and chirp intensity, were not affected by the nymphal food treatment, exposing carrier frequency as the key component indicating past condition. In a previous study we established chirp rate as the sole indicator of current condition. The combined results represent experimental evidence of a multicomponent sexual signal that provides distinct information on male condition during different stages of life.