Average Pupal Weight Research Articles

Resistance Realized Heritability and Fitness Cost of Cyproflanilide in Rice Stem Borer, Chilo suppressalis (Lepidoptera: Pyralidae)

The rice stem borer (RSB) Chilo suppressalis is a devastating rice pest with resistance to a number of insecticides. Recently, the new meta-diamide insecticide cyproflanilide has been considered an effective insecticide to control RSB. However, its resistance risk has not been reported. In the present study, we aimed to assess the resistance risk and evaluate the fitness cost after the RSB was exposed to cyproflanilide. After five generations of selection, the resistance level of RSB increased by 1.5-fold. When h2 was 0.125, a 10-fold resistance increase in the LD50 values was expected in fourteen and thirty-one generations at the selection intensity of 90% and 50%, respectively. The selected population (RSB-SEL) had significant differences in the developmental duration of eggs, 1st, 2nd, 3rd, and 6th instar larvae, and female pupae compared to the unselected population (RSB-UNSEL). Besides, the adult longevity was shortened, and the average pupal weight of males, the emergence rate, the sex ratio, the oviposition, the mean fecundity, and the full life cycle rate were decreased in RSB-SEL. The intrinsic rate of increase (r), the net reproductive rate (R0), and the finite rate of increase (λ) of RSB-SEL were significantly lower than those of RSB-UNSEL, while the mean generation time (T) of RSB-SEL was significantly longer than that of RSB-UNSEL. Based on the results of the prediction of the generations required for a 10-fold resistance increase in the LD50, a potential risk of resistance development exists in RSB after continuous and excessive use of cyproflanilide. These results will be useful in designing the dose of cyproflanilide to control C. suppressalis in field.

Plant quercetin degradation by gut bacterium Raoultella terrigena of ghost moth Thitarodes xiaojinensis.

Associated microbes of several herbivorous insects can improve insect fitness. However, the contribution of specific insect gut bacterium to plant toxin toxification for its host fitness remains scarce. Here, a gut bacterium Raoultella terrigena from the ghost moth Thitarodes xiaojinensis larvae was identified. This bacterium grew unhindered in the presence of Polygonum viviparum, which is a natural food for ghost moth larvae but showed significant growth inhibition and toxicity against Spodoptera litura. S. litura reared on artificial diets containing 5, 15 and 25% P. viviparum powder after 7 days coculture with R. terrigena were found to have shorter larval and pupal durations than on the diets containing P. viviparum powder but without R. terrigena coculture. HPLC analysis revealed that the content of quercetin in mineral medium containing 15% P. viviparum powder after 7 days coculture with R. terrigena was significantly decreased (79.48%) as compared with that in P. viviparum powder without R. terrigena coculture. In vitro fermentation further verified that R. terrigena could degrade 85.56% quercetin in Lucia-Bertani medium. S. litura reared on artificial diets containing 0.01, 0.05 and 0.1 mg/g quercetin after 48 h coculture with R. terrigena were also found to have shorter larval, prepupal and pupal durations, as well as higher average pupal weight and adult emergence rate than on the diets containing quercetin, but without R. terrigena coculture. In addition, R. terrigena was detected in the bud and root tissues of the sterilized P. viviparum, indicating that T. xiaojinensis larvae might acquire this bacterium through feeding. These results demonstrate that the gut bacteria contribute to the degradation of plant toxic molecules to improve the development of herbivorous insects and provide fundamental knowledge for developing effective methods for beneficial insect rearing and pest control.

Effect of Artificial Diet on Immature Stage of the Great Eggfly, Hypolimnas bolina (Lepidoptera: Nymphalidae).

&lt;b&gt;Background and Objective:&lt;/b&gt; One of the Nymphalidae butterfly species found in West Sumatra in &lt;i&gt;Hypolimnas bolina&lt;/i&gt;. Currently, research on the artificial diet for the Nymphalidae butterfly is relatively rare in Padang, West Sumatra. The objectives of this study were to analyze the preferences of &lt;i&gt;H. bolina&lt;/i&gt; larvae, duration of the immature stage and mortality of &lt;i&gt;H. bolina&lt;/i&gt; in artificial diet treatment. &lt;b&gt;Materials and Methods:&lt;/b&gt; Some biological aspects of &lt;i&gt;H. bolina&lt;/i&gt; in corresponding to artificial diet and its effect were investigated in the laboratory. &lt;b&gt;Results:&lt;/b&gt; The result showed that there was no significant difference in the frequency of visits of the larvae in the two diet treatments namely natural (&lt;i&gt;Laportea interrupta&lt;/i&gt; leaves) and artificial diets (Sig = 0.289, p>0.05) but the duration of the visit of &lt;i&gt;H. bolina&lt;/i&gt; larvae was significantly different (Sig = 0.000, p<0.05). The visit duration of the immature stage of &lt;i&gt;H. bolina &lt;/i&gt;was significantly different, except the prepupa and pupal stage. There was no mortality of instar larvae and prepupa stage observed in both of the two-diet treatments. However, the mortality of pupae in an artificial diet was 4%. Of the total of 24 individual larvae fed with artificial diet, all of them successfully emerged, consisted of 12 males and 12 females but there was one male with abnormal wings. The average living period in the artificial diet of imago was 14.82 days for males and 16.77 days for a female. The average larval weight was no significant difference (Sig = 0.981, p>0.05) but the average pupal weight of the natural diet was slightly higher than the artificial diet. &lt;b&gt;Conclusion:&lt;/b&gt; The formulation of an artificial diet is suitable for &lt;i&gt;H. bolina&lt;/i&gt; larvae based on the results of immature mortality and adult emergences. Therefore, the formulation of an artificial diet is suitable for &lt;i&gt;H. bolina&lt;/i&gt; with its composition almost similar to &lt;i&gt;L. interrupta&lt;/i&gt; leaves (natural diet).

Unravelling the role of host plant expansion in the diversification of a Neotropical butterfly genus.

BackgroundUnderstanding the processes underlying diversification is a central question in evolutionary biology. For butterflies, access to new host plants provides opportunities for adaptive speciation. On the one hand, locally abundant host species can generate ecologically significant selection pressure. But a diversity of host plant species within the geographic range of each population and/or species might also eliminate any advantage conferred by specialization. This paper focuses on four Melinaea species, which are oligophagous on the family Solanaceae: M. menophilus, M. satevis, M. marsaeus, and finally, M. mothone. We examined both female preference and larval performance on two host plant species that commonly occur in this butterfly’s native range, Juanulloa parasitica and Trianaea speciosa, to determine whether the different Melinaea species show evidence of local adaptation.ResultIn choice experiments, M. mothone females used both host plants for oviposition, whereas all other species used J. parasitica almost exclusively. In no choice experiment, M. mothone was the only species that readily accepted T. speciosa as a larval host plant. Larval survival was highest on J. parasitica (82.0 % vs. 60.9 %) and development took longer on T. speciosa (14.12 days vs. 13.35 days), except for M. mothone, which did equally well on both host plants. For all species, average pupal weight was highest on J. parasitica (450.66 mg vs. 420.01 mg), although this difference was least apparent in M. mothone.ConclusionWe did not find that coexisting species of Melinaea partition host plant resources as expected if speciation is primarily driven by host plant divergence. Although M. mothone shows evidence of local adaptation to a novel host plant, T. speciosa, which co-occurs, it does not preferentially lay more eggs on or perform better on this host plant than on host plants used by other Melinaea species and not present in its distributional range. It is likely that diversification in this genus is driven by co-occurring Müllerian mimics and the resulting predation pressure, although this is also likely made possible by greater niche diversity as a consequence of plasticity for potential hosts.

Bumblebee pupae contain high levels of aluminium.

The causes of declines in bees and other pollinators remains an on-going debate. While recent attention has focussed upon pesticides, other environmental pollutants have largely been ignored. Aluminium is the most significant environmental contaminant of recent times and we speculated that it could be a factor in pollinator decline. Herein we have measured the content of aluminium in bumblebee pupae taken from naturally foraging colonies in the UK. Individual pupae were acid-digested in a microwave oven and their aluminium content determined using transversely heated graphite furnace atomic absorption spectrometry. Pupae were heavily contaminated with aluminium giving values between 13.4 and 193.4 μg/g dry wt. and a mean (SD) value of 51.0 (33.0) μg/g dry wt. for the 72 pupae tested. Mean aluminium content was shown to be a significant negative predictor of average pupal weight in colonies. While no other statistically significant relationships were found relating aluminium to bee or colony health, the actual content of aluminium in pupae are extremely high and demonstrate significant exposure to aluminium. Bees rely heavily on cognitive function and aluminium is a known neurotoxin with links, for example, to Alzheimer’s disease in humans. The significant contamination of bumblebee pupae by aluminium raises the intriguing spectre of cognitive dysfunction playing a role in their population decline.

Bionomics of overwintering generation of Chilo suppressalis (Walker) in Hunan Province

Chilo suppressalis (Walker) is a serious and destructive rice pest in Hunan Province, China. The diapause larvae of C. suppressalis can successfully overwinter in Hunan Province and the number of overwintering larvae corresponds to the amount of destruction caused in the following year. To properly manage C. suppressalis, it is crucial to survey the number of overwintering larvae and overwintering host plants. Populations of overwintering larvae and overwintering host plants were observed in field surveys from December 2012 to March 2013. Surveys were conducted on grasses, such as Oryza L. (rice) and Zizania latifolia (Griseb.) Turcz. ex Stapf, as well as on weeds and shrubs growing in a rice cultivation area in 14 prefecture-level city in Hunan Province. C. suppressalis larvae were collected from different host plants, including Oryza, Z. latifolia, Zea mays L., Xanthium sibiricum Patr, Miscanthus floridulus (Labnll.) Warb and Coix lacryma-jobi L. These collections were made at different latitudes in Yueyang, Xiangtan, Hengyang and Chenzhou prefecture-level cities in Hunan Province. The pupae were weighed, assessed for differences in overwintering adult fecundity and second generation hatching rate. We found that during this year there were more overwintering larvae in Loudi, Xiangtan and Changsha than other sites in Hunan Province. The largest populations were 15,366 and 11,230 (per 667 m2) overwintering larvae, recorded in Xiangtan and Yueyang, respectively. The larvae's December survival rate ranged between 75.38% and 93.87%, and decreased slightly over the next few months, which fluctuated between 70.26 and 89.27. Eleven different plant species in Hunan Province, such as rice, Z. latifolia, and field ridges were chosen by larvae as hibernaculum. This study is the first record of X. sibiricum, M. floridulus, Nelumbo nucifera Gaertn., C. lacryma-jobi, Ambrosia artemisiifolia Linn. and Bidens pilosa Linn. as hibernaculum for C. suppressalis in Hunan Province. The developmental progression of larvae was highly synchronous in that most larvae were at the 4th instar stage in December and January, while half of the larvae were in the 5th stage in February and 60% of the larvae reached the 6th stage in March. There were no significant differences in pupal weight among the 14 prefecture-level cities surveyed in Hunan Province, but there were temporal differences in larval development. In southern Hunan Province (Hengyang, Youzhou and Chenzhou) the 50% pupal (April 6th–12th), adult emergence (April 17th–May 24th) and peak hatching (May 1st–5th ) stages occurred 10 days earlier than they did in populations in the northwestward sites (Jishou and Zhangjiajie). However, significant differences in C. suppressalis pupal weight were observed when they were contrasted according to their hibernacula. Average pupal weights were highest on Zizania caduciflora (64.21 mg) and Oryza (51.52 mg). However, neither the hibernacula nor the latitude corresponded to significant differences in overwintering adult fecundity and second generation hatching rates. Our results indicate that many C. suppressalis choose rice stubble as a hibernaculum and treatment of rice stubble on a large scale would be a useful component to the integrated control of this pest. Besides rice stubble, the diversity of overwintering host plants may serve as trap crops to control populations of C. suppressalis in rice fields and there should be further research in this area. In the meantime, our results suggest that prefecture-level city plant protection station staff should invest in surveys of overwintering C. suppressalis larvae population sizes and overwintering host plants as reasonably accurate forecasts of C. suppressalis populations for the coming year. These surveys can act as a basis for planning local cropping systems and selecting the proper varieties of rice to plant.

Desenvolvimento e reprodução da mosca-do-mediterrâneo em caquizeiro, macieira, pessegueiro e videira

O objetivo deste trabalho foi descrever o desenvolvimento e reprodução de Ceratitis capitata (Diptera: Tephritidae) em frutos de caqui 'Fuyu', maçã 'Gala', pêssego 'Maciel' e uva 'Itália'. Foram feitas avaliações quanto a: duração e viabilidade do ovo, duração do estágio larval, peso de pupa, duração e viabilidade da pupa, duração do período ovo-adulto, razão sexual, período de pré-oviposição e oviposição, fecundidade diária e total e longevidade de machos e fêmeas. A maior duração do período ovo-adulto ocorreu em maçã, em consequência do aumento do estágio larval, seguido por uva, caqui e pêssego. Larvas que se alimentaram de pêssego apresentaram maior peso médio de pupa. A maior viabilidade pupal foi registrada em pêssego, equivalente à de uva e caqui. O período de pré-oviposição foi maior para fêmeas provenientes de maçã e uva. Fêmeas provenientes de pêssego apresentaram período de oviposição mais longo, além de maior fecundidade média diária e fecundidade total. A longevidade de adultos foi superior em insetos criados em pêssego. Frutos de pessegueiro são mais adequados para o desenvolvimento de C. capitata, em comparação aos de caqui, maçã e uva.

Occurrence and biology of Tolype innocens (Burmeister) on blueberry

Tolype innocens (Burmeister, 1878) is reported for the first time damaging blueberry (Vaccinium ashei) plants in Brazil having the caterpillars feeding on leaves and new shoots. T. innocens biology was studied on blueberry leaves in laboratory conditions and then a fertility life table was elaborated. Developmental time and viability of egg, larval and pupal stages and egg-adult period were 15.0 and 35.3, 33.3 and 84.5, 20.6 and 100, and 69.2 days and 45%, respectively. Average pupal weight was 0.840g for the females and 0.580g for the males. The sex ratio was 0.5. Pre-oviposition and oviposition time lasted 6.34 and 12.1 days, respectively. Mean fecundity was 251 eggs per female. Eggs were laid either individually or in masses. Longevity was 19.0 and 20.0 days for males and females, respectively. T. innocens population increased 47 times per generation, with a mean generation time of 77 days, and a finite rate of increase of 1.02. This data on biological parameters will be useful for establishing control strategies.

INFLUENCE OF HERBAL TONIC ALLOE ON THE OVERALL PERFORMANCE OF THE MULBERRY SILKWORM, BOMBYX MORI L.

ABSTRACT The influence of the dietary supplementation of the herbal tonic “Alloe” containing principally the extract of Aloe vera Linne. on the growth and the cocoon characteristics of the mulberry silkworm Bombyx mori L. commercial cross breed race L x CSR2 during its fifth instar was experimented. This, in general, elicited better response of the growth and the cocoon characteristics of this silkworm. Specifically, the Aloe vera tonic at 2.0 per cent concentration resulted higher larval growth and increased the weight of cocoon. The mean larval weight, relative growth rate, effective rearing rate, larval consumption index of the final instar larvae of B. mori increased with this supplementation of Aloe vera tonic. The average pupal weight and mother moth weight also increased as a result of this supplementation. Maximum shell weight and shell ratio were noted in the experimental sets treated with the A. vera tonic. In addition, the fibroin content of the cocoon shell produced by this silkworm in response to the dietary supplementation of Aloe vera tonic treatment also showed significant increase over the control The overall performance of Bombyx mori in response to this A. vera tonic treatment observed in the present study and the evaluation index values worked out showed that the growth and the cocoon parameters could be improved with the supplementation of A. vera commercial preparations.

Growth Inhibitory Activity of Fatty Acid Methyl Esters in the Whole Seed Oil of Madagascar Periwinkle (Apocyanaceae) Against &lt;I&gt;Helicoverpa armigera&lt;/I&gt; (Lepidoptera: Noctuidae)

Crude hexane and water extracts of Catharanthus roseus Linn. (Syn: Vinca rosea) (Apocyanaceae) stem, leaf, and seed exhibited pesticidal activity against Helicoverpa armigera (Hübner) (Lepidoptera Noctuidae). The extracts differed significantly in their efficacy, with the crude hexane extract of whole seed being the most effective in curtailing pupal survivorship to 18% followed by the hexane extracts of leaf (21%) and stem (24%). Average pupal weight (68.2 mg) and length (1.5 cm) in the whole seed treatment were drastically reduced, compared with the controls (415.2 mg and 2.72 cm), subsequently reducing adult emergence to 15.7%. SiO2 column purification yielded eight fractions of which fraction 1 exhibited 90% larval mortality, with severe reduction of the larvae weight (12.7 mg) and length (1.5 cm). Gas chromatographic-mass spectrometric analysis of fraction 1 suggested the presence of 16 compounds, among which oleic, linoleic, palmitic, and margaric acids were detected as major constituents. Presence of the alkane hydrocarbons triacontane, tetracosane, and heptacosane also was noted.

Host plant resistance in romaine lettuce affects feeding behavior and biology of Trichoplusia ni and Spodoptera exigua (Lepidoptera: Noctuidae).

Lettuce quality and yield can be reduced by feeding of several lepidopterous pests, particularly cabbage looper, Trichoplusia ni (Hübner), and beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Host plant resistance to these insects is an environmentally sound adjunct to conventional chemical control. In this study we compared the survival, development, and feeding behavior of cabbage looper and beet armyworm on two romaine lettuce cultivars, resistant 'Valmaine' and susceptible 'Tall Guzmaine'. Larval mortality of both species was significantly higher on resistant Valmaine than on susceptible Tall Guzmaine. The average weight per larva after feeding for 1 wk on Tall Guzmaine plants was 6 times (beet armyworm) and 2 times (cabbage looper) greater than that of larvae feeding on Valmaine plants. Significant reduction in larval growth on Valmaine compared with that on Tall Guzmaine resulted in a 5.9- (beet armyworm) and 2.6-d (cabbage looper) increase in larval duration and almost a 1-d increase in pupal duration. Average pupal and adult weights and successful pupation of cabbage looper and beet armyworm were reduced on Valmaine compared with Tall Guzmaine. The sex ratio of progeny did not deviate from 1:1 when larvae were reared on either Valmaine or Tall Guzmaine. The fecundity of cabbage looper and beet armyworm adults that developed from larvae reared on Valmaine was about one-third that of adults from Tall Guzmaine, but adult longevity did not significantly differ on the two lettuce cultivars. The two insect species showed different feeding preferences for leaves of different age groups on Valmaine and Tall Guzmaine. Cabbage loopers cut narrow trenches on the leaf before actual feeding to block the flow of latex to the intended site of feeding. In contrast, beet armyworms did not trench. The different feeding behavior of the two species on Valmaine may explain the superior performance of cabbage looper compared with beet armyworm.

Comparison of Common Milkweed and Honeyvine Milkweed (Asclepiadaceae) as Host Plants for Monarch Larvae (Lepidoptera: Nymphalidae)

Abstract Two species of milkweed (Asclepiadaceae) are especially abundant in portions of eastern North America. Common milkweed, Asclepias syriaca L., is most abundant in the northern United States and southeastern Canada, while honeyvine milkweed, Cynanchum laeve (Michaux), is most abundant at central latitudes in the eastern half of the United States. The former is frequently cited as an important host plant for larvae of the monarch butterfly, Danaus plexippus L. (Lepidoptera: Nymphalidae), while the latter is rarely mentioned in this regard. We compared the performance of monarch larvae on these two plant species. Larvae developed significantly faster on honeyvine milkweed than on common milkweed. Average pupal fresh weights appeared to be slightly greater for individuals reared on common milkweed than those reared on honeyvine milkweed, but the difference was not statistically significant. Similarly, larval survival was about 14% higher on common milkweed, but the difference was not significant. Our ...

The Botanophila–Epichloë association in cultivated Festuca in Oregon: evidence of simple fungivory

AbstractWe investigated the Botanophila (Diptera: Anthomyiidae)–Epichloë (Ascomycetes: Clavicipitaceae) interaction in cultivated Festuca spp. (fine fescue) in Oregon in western USA. Epichloë spp. are endophytic fungi of grasses in the subfamily Pooideae. They develop a felt‐like stroma on the surface of grass culms and a dense mycelium within the culms that typically prevents seed head emergence. As a result, seed yields are suppressed, and hence the disease is known as choke. Studies of Epichloë spp. on wild grasses indicate that the fly–fungus interaction is an obligatory mutualism. During oviposition, Botanophila transfers Epichloë spermatia between stromata of opposite mating types, and the perithecia that develop after fungal fertilization serve as food for Botanophila larvae. In the current study, we surveyed 19 cultivated fields of Festuca spp. in Oregon, and observed choke caused by Epichloë festucae Leuchtmann, Schardl and Siegl in 10 of these. However, perithecia were observed in only four fields, and on only 1.0–2.6% of stromata. Perithecial development was also low, and rarely covered 50% of the stroma surface. Despite the absence or low frequency of fertilized stromata, Botanophila lobata Collin larvae were present in all choke‐infested fields. Infestation levels ranged from 2.5 to 70.7%, based on an examination of 175–200 stromata from each field. Only eight (= 2%) of the 450 stromata with B. lobata had perithecia, and the greater majority of B. lobata larvae completed development and exited from unfertilized stromata. This is the first report of the B. lobata–E. festucae association in the USA, and of B. lobata larvae developing successfully on unfertilized Epichloë stromata. The average pupal weight (0.0032 g) did not differ significantly from pupae (0.0030 g) originating from larvae that had developed on fertilized stromata of E. typhina on Dactylis glomerata in a neighboring field. This result indicates that in cultivated fine fescue fields in Oregon, B. lobata forages on E. festucae, but fly development is not dependent on the fertilized stromata of Epichloë.

Postlarval fitness of transgenic strains of Cochliomyia hominivorax (Diptera: Calliphoridae).

Eight transgenic strains of Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) were compared with the wild-type parental laboratory strain (P95) in colony. Measurements of average weight of pupae, percentage of adults emerging from pupae, ratio of males to total emerged adults, and mating competitiveness were analyzed. The parental strain colony was subcultured and exposed to handling procedures equivalent to transgenic strains for valid comparison of overall colony fitness. None of the transgenic colonies exhibited significantly lower fitness characteristics than the control parental colony. One transgenic colony had a higher ratio of adults emerging from pupae, and five colonies had higher average pupal weight; because fitness cost would only be indicated by lower values, the statistical variations were not significant. Males of one transgenic strain were shown to mate with equal frequency compared with males of the parental strain. Hence, the presence of the transgene used to produce the strains tested did not incur a fitness cost to the colonies of laboratory-reared C. hominivorax.

Postlarval Fitness of Transgenic Strains of Cochliomyia hominivorax (Diptera: Calliphoridae)

Eight transgenic strains of Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) were compared with the wild-type parental laboratory strain (P95) in colony. Measurements of average weight of pupae, percentage of adults emerging from pupae, ratio of males to total emerged adults, and mating competitiveness were analyzed. The parental strain colony was subcultured and exposed to handling procedures equivalent to transgenic strains for valid comparison of overall colony fitness. None of the transgenic colonies exhibited significantly lower fitness characteristics than the control parental colony. One transgenic colony had a higher ratio of adults emerging from pupae, and five colonies had higher average pupal weight; because fitness cost would only be indicated by lower values, the statistical variations were not significant. Males of one transgenic strain were shown to mate with equal frequency compared with males of the parental strain. Hence, the presence of the transgene used to produce the strains tested did not incur a fitness cost to the colonies of laboratory-reared C. hominivorax.

The role of host plant phenology in the development of the oak leafroller moth, Tortrix viridana L. (Lepidoptera: Tortricidae)

Phenological coincidence between the insect and its host plant was studied in natural environment. Two phenological events were controlled: degree to which larval eclosion coincided with budburst in oaks, and synchrony between the duration of the insect development and growth of host plant leaves. Both factors varied from one season to another, and among the early, normal and late-flushing trees. These two phenological factors were compared in respect to their effect on the herbivore, using average pupal weights and densities as estimations of the insect success. Developmental synchrony to host plant appeared to be of a decisive importance for the successful development of the insect larvae. In contrast, the synchrony between eclosion and budburst did not influence strongly pupal weights and densities in given case, when variation in bud-flushing dates (about 10 days) did not exceed the T. viridana ability to resist starvation under the spring conditions. Two distinct peaks of larval eclosion from the eggs, collected in winter, were registrated under constant laboratory conditions. The larvae tended to hatch earlier on the trees with higher rates of average leaf growth (2-year data). Thus, two sympatric populations of the herbivore, differing in the dates of egg hatching, coexist in the same area.

INSECTS AND TEMPERATURE—DIFFERENTIAL EFFECTS OF EXPERIMENTAL CONDITIONS ON GROWTH AND DEVELOPMENT

AbstractCohorts of Pieris rapae (L.) (Lepidoptera: Pieridae) were reared at different temperatures on three substrates: plants in growth chambers, plants in field cages, and artificial medium. Pupal weight and larval development times were measured. The data were analyzed to determine the effect of temporal changes in substrate on pupal weight. When cohorts were reared on whole plants, average pupal weight declined with increasing time to pupation. For cohorts on potted plants in growth chambers, the rate of decline decreased as temperature increased from 15 to 27 °C. But, for cohorts on plants in field cages, the rate of decline increased as temperature increased from 16 to 25 °C. We speculate that the former trend resulted from plant deterioration, especially at low temperatures, and the latter from larval competition at high temperatures. When larvae were reared on potted plants to the late II or early III instar and then transferred to artificial medium, deterioration of the medium at temperatures below 20 and above 27 °C caused pupal weight to decline significantly with increasing time to pupation, whereas between 20 and 27 °C, pupal weight was constant or increased with increasing time to pupation. Development times of larvae from cohorts reared on plants in growth chambers showed no consistent differences from those of larvae from cohorts reared on artificial medium, at any temperature (overall averages: 187 and 184 day-degrees above 10 °C, on plants versus medium). Pupal weights are determined by the ratio of growth rate to development rate (Appendix). Therefore, the observed differences in pupal weight reflect differences in growth rates rather than differences in development rates. The results show that, depending on temperature, substrate deterioration may seriously affect laboratory studies of herbivore growth and that there are important interactions between temperature and host-plant growth conditions that may make extrapolation of laboratory estimates of herbivore growth to field conditions tenuous.

Survival and development of Chilo partellus (Swinhoe) on sorghum cultivars

AbstractSurvival and development of Chilo partellus were studied on five sorghum cultivars (IS-18363, IS-18520, ICS-1, ICS-2 and IS-4660) in the laboratory at Mbita Point Field Station, Kenya, at 26 ± 2°C and 65 ± 5% RH. Larval developmental period differed significantly on different cultivars. Number of instars was numerically greater for the females than for the males on all cultivars. Average pupal weight varied with sex; females were twice as heavy as males. The pupal period was longer for males than for females on all cultivars, with the exception of ICS-1, where the pupal period of males was equal to that of females. Ovipositional period was significantly longer on IS-18520 (5.18 ± 0.30 days) than on other cultivars. The shortest ovipositional period (3.70 ± 0.27 days) was recorded on IS-4660. There were no statistically significant differences in adult longevity. Sex ratio of the moths also did not affect the adult longevity of C. partellus reared on the five sorghum cultivars. The variations found in the development of C. partellus on different cultivars were attributed to the nutritional value of the food source.

Relationship between selected bacteria and the growth of immature house flies, Musca domestica, in an axenic test system.

To investigate the relationship between immature (maggot) house flies, Musca domestica, and bacteria, we compared the development of sterile first-instar maggots in each of 10 pure blood agar cultures of bacteria with growth on sterile blood agar (negative control) and on standard house fly rearing medium (positive control). Nine species of bacteria representing gram-negative and gram-positive rods, coccoid, and micrococcoid cell types supported house fly growth on blood agar. One bacterium, a strain of Bacillus cereus, inhibited maggot growth. The percent pupation for maggots that developed in the presence of eight of nine bacteria (range, 41-69%), was significantly greater than in sterile blood agar (0-5%), and did not differ significantly from maggot growth in the rearing medium (50-90%). Average pupal weight for maggots that developed on blood agar with bacteria ranged from 19 to 21 mg, a reflection of favorable growth conditions. Average pupal weight in the presence of three bacteria (19.9, 19.4, and 19.4 mg) was significantly less than respective pupal weights in house fly rearing medium (24.0, 22.3, and 22.1 mg), but there was no difference in average pupal weight with six bacteria and the house fly rearing medium. These findings illustrate that bacteria or their metabolic products are essential as nutrients for house fly maggot growth in blood agar; a wide variety of adventitious bacteria can contribute to the suitability of an organic substrate for maggot growth; and a naturally occurring isolate of B. cereus limits house fly maggot growth in blood agar, a relationship that has not been reported previously.

Reduced Larva Growth of Two Lepidoptera (Noctuidae) on Excised Leaves of Soybean Infected with a Mycorrhizal Fungus1

Soybean roots were infected by the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum or were left noninoculated and fertilized with phosphorus (P). Detached leaves of infected plants were fed to neonate larvae of corn earworm, Heliothts zea (Boddie), or fall armyworm, Spodoptera frugiperda (J. E. Smith). Average weights of larvae after 14 days were reduced by 40% relative to larvae fed P-fertilized (control) soybean leaves. Larvae of both species fed leaves from VAM plants took longer to pupate, average pupal weights were lower, and mortality was greater than for larvae that received control leaves. Growth reduction for larvae fed VAM leaves was not correlated with leaf nitrogen, amino acid, carbohydrate, micronutrient, or phenolic content. The extent of VAM-fungal infection of soybean roots varied between cultivars, and percent fungal infection was positively correlated with delays in pupation and negatively correlated with growth differences. We could not discern whether the basis of the mycorrhizal effect was due to induction of an anti-feedant, a toxic factor, or due to changes in the nutritional quality of the host plant’s leaves.