Role of Challenger pesticide and plant extracts on some physiological parameters of the cotton leafworm,Spodoptera littoralis (Boisd.)

Fourth instar larvae of cotton leafworm, Spodoptera littoralis (Boisd.), fed on castor bean leaves treated with sub-lethal concentrations of both alcohol and hexane extracts of Egyptian conyza and Challenger 36% SC insecticide as well to study their effects on mortality, food consumption and utilisation of food. The tested insecticides exhibited relatively high mortality in alcoholic extract of Egyptian conyza (5.0% concentration) followed by Challenger (1.0% concentration). Results showed a slight reduction in the consumption index for larvae treated with both alcoholic extract and Challenger at low concentrations, while hexane extract (5%) recorded significant increase. The approximate digestibility (AD) was reduced in all treatments of alcoholic extract and the relative growth rate insignificantly decreased at 5% concentration, whereas AD increased for larvae fed on Challenger 0.25% concentration. The lower concentration of alcoholic extract of conyza and all treatments of Challenger pesticides induced insignificant decrease in the efficiency of conversion of the ingested food, while hexane extract exhibited insignificant increase. Challenger at all tested concentrations achieved insignificant decrease in the efficiency of the conversion of digested food with respect to the control.     

Ectopically expressed leaf and bulb lectins from garlic (<Emphasis Type="Italic">Allium sativum</Emphasis> L.) protect transgenic tobacco plants against cotton leafworm (<Emphasis Type="Italic">Spodoptera littoralis</Emphasis>)

The insecticidal activity of the leaf (ASAL) and bulb (ASAII) agglutinins from Allium sativum L. (garlic) against the cotton leafworm, Spodoptera littoralis Boisd. (Lepidoptera: Noctuidae) was studied using transgenic tobacco plants expressing the lectins under the control of the constitutive CaMV35S promoter. PCR analysis confirmed that the garlic lectin genes were integrated into the plant genome. Western blots and semi-quantitative agglutination assays revealed lectin expression at various levels in the transgenic lines. Biochemical analyses indicated that the recombinant ASAL and ASAII are indistinguishable from the native garlic lectins. Insect bioassays using detached leaves from transgenic tobacco plants demonstrated that the ectopically expressed ASAL and ASAII significantly (P < 0.05) reduced the weight gain of 4th instar larvae of S. littoralis. Further on, the lectins retarded the development of the larvae and their metamorphosis, and were detrimental to the pupal stage resulting in weight reduction and lethal abnormalities. Total mortality was scored with ASAL compared to 60% mortality with ASAII. These findings suggest that garlic lectins are suitable candidate insect resistance proteins for the control of S. littoralis through a transgenic approach.     

Untersuchungen zur Veränderung der Unkrautflora bei mehrmaligem Getreidenachbau auf einer Tonschwarzerde des Thüringer Beckens

The latent effects of precocenes I and II (PI and PH) and juvenile hormone I (JHI) when topically applied to the last three instars of Spodoptera littoralis (Boisd.) larvae have been studied. Application of both PI or PII resulted in morphogenetic abnormalities resemble some effects induced by administration of JHI, e.g., larval‐pupal intermediate, partial or severe cases of untanned pupae and imperfect moths. In PII‐treatments, the effect was instar‐dose‐dependent. The intermediate dose (55 μg) was more effective on S. littoralis larvae than other doses. The effectiveness of both doses of 40 or 70 μg in production of deformed larvae and pupae decreased when applied as repeated doses instead of single ones. In Pi‐treatments, the lower dose (25 μg) was more harmful to Spodoptera larvae than the higher dose (70 μg). Repeated application by either lower or higher doses did not enhance the production of imperfect insects. Application of JHI induced symptoms ranging from supernumerary instars, larval‐pupal intermediate, untanned pupae and deformed adults. The effect was dose‐dependent. In all tested compounds, there apparently was a latent or delayed effects. Although the insects were treated while they were larvae the complete effects were not apparent until after the insect had become a pupa or an adult. More efforts will be needed to understand how does precocene interferes with the process of tanning or sclerotization?     

Potency of Bacillus thuringiensis and Bacillus subtilis against the cotton leafworm,Spodoptera littoralis (Bosid.) Larvae

The biological activities of two species of bacteria isolated from soil of cotton fields identified as Bacillus subtilis strain NRC313 (BS NRC313) and Bacillus thuringiensis strain NRC335 (BT NRC335) were evaluated against the third larval instar of the cotton leafworm, Spodoptera littoralis (Boisd.). The different entomopathogenic bacteria of BS NRC313and BT NRC335 contained 10 × 10⁸ cell/ml, and caused mortality of 100 and 97.3% for the above mentioned strains, respectively. Concentrations of 2.5 × 10⁸ to 10 × 10⁸ cell/ml of strains BS NRC313 and BT NRC335 were applied to the larvae: LC₅₀ were 3.3 × 10⁸ and 3.9 × 10⁸ cell/ml respectively. The influence of exposure to toxin concentrations manifested in terms of decreasing the adult emergence and prolongation of the generation period. The percentage of larvae that survived and succeeded to pupate increased by decreasing the concentration. The longevity of adult emergence that resulted from larvae treated with Bacillus subtilis were 6.0 ± 0.51 and 9.0 ± 0.63 days at 5 × 10⁸ and 2.5 × 10⁸ cell/ml, respectively compared with 9.8 ± 0.47 in control. The results indicated that Bacillus subtilis was more potent than Bacillus thuringiensis. Field applications of B. thuringiensis, B. subtilis and Reldan achieved 55.6, 67.4 and 89.4% reduction of the cotton leafworm larvae Spodoptera littoralis in clover plants under field conditions.     

A possible therapy by juvenile hormone I to Spodoptera littoralis (Boisd.) larvae previously treated by precocene II

An effective constant dose (55 μg) of precocene II (PII) was topically tested against the last three instars of Spodoptera littoralis (Boisd.) larvae. Application of PII induced morphogenetic abnormalities typical of juvenile hormone (JH) excess. The resultant imperfect insects included larval‐pupal mosaic and partial or severe cases of untanned pupae. The sixth‐instar larvae were more sensitive to PII administration than the two preceding instars. However, sensitivity of the last larval instar to PII varied with the timing of dose application relative to the developmental status of the larvae. Whereas the newly ecdysed (0‐day old) larvae were more sensitive, the older larvae of the same sixth‐instar showed sharp decrease in their sensitivity to PII with a concomitant increase of their age. Application of a single dose (5 μg) of JH I to PII pre‐treated larvae significantly (P < 0.001) reduced the production of imperfect insects where many PH‐treated larvae developed successfully to apparent normal pupae. Although a single dose of PII was more effective on S. littoralis larvae than repeated daily doses, the effectiveness of JHI‐therapy to PH pre‐treated larvae by repeated doses was less effective in producing perfect insects than JH‐therapy to PII pre‐treated larvae by single doses. The reversal of any of these by applied JHI is quite interesting but the mechanisms remain to be unraveled.     

Biological performance of quercetin on the cotton leaf-worm larvae, Spodoptera littoralis Boisd. (Lep., Noctuidae) and prevailing natural enemies in the Egyptian cotton fields

The Egyptian cotton (Gossypium barbadense L.) accounts for 65 % of the world production of long stable cultivars. Taking into consideration the competition of other cotton producing countries, it should be of great importance to control pests, which attack the cotton plants to improve the yield and its quality. The main objective of this study is to develop new approaches for the management of the cotton leafworm Spodoptera littoralis Boisd. within an IPM program, that include synthetic insecticides rationalization, and maximiziation the role of the biological control agents. Sunflower plants Helianthus annuus (Asterales: Asteraceae) raised in rows surrounding plots of cotton were used as trap plants to attract some biological agents, which subsequently lead to check the build-up of the cotton leafworm population. This scientific phenomenon was attributed to the main chemical constituent of sunflower plants, which has been proved to be the polyhydroxy flavone "quercetin". Field data of the two successive seasons 2004 and 2005 revealed that: (a) the total number of insect predators, Coccinella undecimpunctata, Paederus alfierli, Chrysopa vulgaris, Orius laevigatus, Scymnus synacus, and true spiders in the cotton plots surrounded by either one or two rows of sunflower plants significantly exceeded the corresponding numbers in the cotton plots without sunflower plants., (b) the least number of cotton leafworm Spodoptera littorolis larvae infestation was recorded simultaneously in the cotton plots surrounded by sunflower plants. Moreover, laboratory studies assured the antifeeding properties of quercetin against the 4th instar larvae of Spodoptera littoralis. Quercetin at a concentration rate of 4000 ppm, showed abnormal behaviour represented in feeding stop, growth inhibition and development retardation. Deformation of pupae, moths, and reduction up to 50% in egg laying was also noticed after quercetin application to the larvae.     

Transgenerational effects modulate density-dependent prophylactic resistance to viral infection in a lepidopteran pest

There is an increasing appreciation of the importance of transgenerational effects on offspring fitness, including in relation to immune function and disease resistance. Here, we assess the impact of parental rearing density on offspring resistance to viral challenge in an insect species expressing density-dependent prophylaxis (DDP); i.e. the adaptive increase in resistance or tolerance to pathogen infection in response to crowding. We quantified survival rates in larvae of the cotton leafworm (Spodoptera littoralis) from either gregarious- or solitary-reared parents following challenge with the baculovirus S. littoralis nucleopolyhedrovirus. Larvae from both the parental and offspring generations exhibited DDP, with gregarious-reared larvae having higher survival rates post-challenge than solitary-reared larvae. Within each of these categories, however, survival following infection was lower in those larvae from gregarious-reared parents than those from solitary-reared, consistent with a transgenerational cost of DDP immune upregulation. This observation demonstrates that crowding influences lepidopteran disease resistance over multiple generations, with potential implications for the dynamics of host–pathogen interactions.     

Laboratory evaluation of a new strain CCM 8367 of Isaria fumosorosea (syn. Paecilomyces fumosoroseus) on Spodoptera littoralis (Boisd.)

Laboratory experiments were conducted to assess the efficiency of the new strain CCM 8367 of Isaria fumosorosea on different stages of the Egyptian cotton leafworm, Spodoptera littoralis (Boisd.), including soil treatments with pre-pupal and pupal stages. Treatments of larval instars showed a high susceptibility with 3rd, 5th and last instars to suspension of this fungus with concentration 5?×?10⁷ spores/ml. Larval mortality was over 90%. There were no significant differences (P?=?0.7929, F?=?0.2346) between instar treatments. The commercial fungus, PreFeRal® strain Apopka 97 of I. fumosorosea, which was used in comparison with this new strain caused mortality rates of between 63.33 and 90%. Statistically, differences between the effects of CCM 8367 strain and Apopka 97 were highly significant on the last instar (P?=?0.0064, F?=?6.479) and extremely significant on the 3rd instar (P?<?0.0001, F?=?13.29). No significant differences were recorded between the two strains on the 5th instar (P?=?0.0597, F?=?3.233). Fungal treatments with the late stage insects (end of the last instar or pupal stage) in soil yielded interesting results: the mortality rate on end of final instar larvae was 16.66% when treated with Apopka 97 and 83.33% when treated with CCM 8367. Soil containing pupae of S. littoralis that were inoculated with CCM8367 resulted in a high number of malformed adults, and the mortality rate was 64.52% (32.27% of malformed adults died and 32.25% of pupae fully infected by fungus). Only 3.23% of samples produced morphologically normal adults in this test. The results conclude that the strain of I. fumosorosea CCM 8367 has strong insecticidal effects on S. littoralis and has the potential to be implemented as a novel biocontrol agent.     

Fungi associated with the Egyptian cotton leafwormSpodoptera littoralis Boisdoval

A total of 28 species representing 15 fungal genera were found to be associated with the all different stages of the Egyptian cotton leafworm,Spodoptera littoralis Boisd., its faeces and the air of the containers where it was reared on Czapek Dox agar medium at 28°C.Aspergillus was the most common genus and was frequently isolated from all substrates.A. flavus was the only fungus associated with all insect stages. At least two well known facultative pathogens were obtained:Beauveria alba andCephaliophora tropica. Nearly all fungi recovered from insect faeces or its environment were also encountered from different insect stages. Forty-two isolates were tested for their abilities for growth on a synthetic medium (nitrogen- and carbon-free) containing partially purified chitin. Most (76.2%) had moderate growth rates.     

Sensibilité des larves deSpodoptera littoralis [Lep.: Noctuidae] aux hyphomycètes entomopathogènesNomuraea rileyi etPaecilomyces fumoso-roseus

Résumé L'étude de la sensibilité des chenilles deSpodoptera littoralis Boisd. à des doses croissantes de spores deNomuraea rileyi (F.)Samson, montre que le 6^e et dernier stade est plus résistant que le 1^er et surtout les 4^e et 5^e stades larvaires. La virulence du pathotypeN. rileyi n^o 5 à l'égard des larves de cette noctuelle est élevée puisque le temps léthal 50 % (TL 50) est de 6 j en moyenne. Pendant l'incubation de la maladie les chenilles continuent de s'alimenter mais l'infection peut réduire jusqu'à 60 % la prise alimentaire par rapport à la consommation des larves des lots témoins. Toutes conditions égales par ailleurs, la mortalité provoquée parN. rileyi n^o 5 après traitement des larves nouvelles-nées est supérieure lorsque les insectes sont maintenus à 25°C par rapport à celle constatée à 20°C. Cependant pour une dose d'inoculum élevée, les conditions thermiques (20°, 25° ou 28°C), ne modifient pas sensiblement la réponse à l'infection parN. rileyi n^o 5 alors qu'elles limitent l'efficacité d'un pathotype moins virulent:Paecilomyces fumoso-roseus Wize no^o 39.

---

Summary Laboratory studies were conducted to determine the susceptibility of various larval instars of the cotton leafworm,Spodoptera littoralis Boisd. to different spore doses ofNomuraea rileyi (F.)Samson to investigate the influence of temperature on the infection by this fungus and byPaecilomyces fumosoroseus Wize. Contaminations were obtained by direct spraying on larvae in tower apparatus or by feeding of larvae on treated pieces of leaf during 48 h or 72 h. The influence of cryptogamic infection on food consumption was studied by measuring surfaces of standard cabbage leaf disces submitted to treated and control larvae. Angular values mortality rates were submitted to the 2- or 3-way analysis of variance and comparisons of means were made by theDuncan's test. In some cases we have also considered the time-mortality and the dose-mortality curves. The 6th instar was more resistant than all other tested instars. TL50 were found to be 6 days in most cases. During incubation of the disease, larvae continued to feed, but food consumption could be reduced at 40 % of controls. Larval mortality due toN. rileyi N^o 5, recorded after 8 days of incubation, was higher at 25°C than at 20°C. Nevertheless, at high dosage, efficiency ofN. rileyi N^o 5 was not affected by temperature at 20°, 25° and 28°C. The other pathotype,P. fumoso-roseus N^o 39 was more effective at 20°C than at 25° and 28°. At 32°C, the temperature, unfavourable to fungal growth, limited mortality at non significant rates.

---

---

Avec la collaboration technique deH. Vermeil de Conchard.     

Age-related cannibalism and horizontal transmission of a nuclear polyhedrosis virus in larval Spodoptera frugiperda

1. Experiments were carried out to investigate the incidence of cannibalism throughout the larval development of the noctuid moth Spodoptera frugiperda, and to examine the risk of infection from consuming conspecifics infected with a nuclear polyhedrosis virus (SfNPV). 2. Cannibalism was observed commonly even when food was not limiting, but occurred more frequently at low food quantities and/or high rearing densities. The sex of the larvae had no effect on the incidence of cannibalistic behaviour, however the probability of cannibalism occurring was affected by larval stage. The frequency of cannibalism was significantly higher among fifth- and sixth-instar larvae than among earlier instars, and larvae were more likely to consume younger conspecifics than larvae of the same stage. 3. Fifth-instar larvae offered fourth-instar victims fed equally on healthy larvae, virus-infected larvae (2 days post-infection), uninfected corpses, and virus-killed corpses (6 days post-infection). Horizontal transmission of SfNPV was only recorded in larvae offered virus-killed corpses, however, and total mortality in this treatment was only 32%. 4. In a similar experiment, fourth-instar larvae avoided cannibalising virus-killed corpses. Horizontal transmission of SfNPV was recorded in fourth-instar larvae that consumed 2-day post-infected larvae. The low incidence of cannibalism observed in fourth-instar larvae, however, suggests that this is unlikely to provide an important route for the transmission of SfNPV.     

Prediction studies on number of teratocytes and eggs of Microplitis rufiventris Kok. (Hym., Braconidae) parasitoid in superparasitized host larvae

Microplitis rufiventris Kok. (Hym., Braconidae) is an internal solitary parasitoid of many noctuid caterpillars including the cotton leafworm Spodoptera littoralis (Boisd.) ( Kokujev 1914 ; Hammad et al. 1965 ; Gerling 1969 ), the lesser cotton worm S. exigua Hbn. ( Meier 1929 ; Thompson 1946 ; El-Minshawy 1963 ); S. latebrosa Lederer ( Hammad et al. 1965 ) and American bollworm Heliothis armigera Hbn. ( Meier 1929 ; Ibrahim & Tawfik 1975 ). When the egg of M. rufiventris hatches in its host, S. littoralis, spherical cells from the serosa that envelope the parasitoid embryo are released into the host’s haemolymph. Approximately 400 cells are liberated from an egg of the parasitoid. These cells increase in size, reaching a maximum average diameter of 137 μm at the completion of parasitoid development ( Khafagi 1997 ). These cells are most frequently called ‘teratocytes’ ( — 1968 , 1971; Vinson 1970 ). It is reported that the presence of large numbers of the teratocytes is indicative of superparasitism but their number does not give an indication to the exact number of parasitoid eggs from which the cells have been derived ( —, — Khafagi et al. 1998 ) . Therefore, it was of interest to initiate prediction studies on egg and teratocyte numbers in superparasitized host larvae.     

Protection of potato crop against Phthorimaea operculella (Zeller) infestation using frass extract of two noctuid insect pests under laboratory and storage simulation conditions

The oviposition deterrent effect of water extract of Spodoptera littoralis and Agrotis ipsilon larval frass on Phthorimaea operculella adult females was studied using two types of larval food “Natural host and Semi-artificial diet” under laboratory and storage simulation (semi-field) conditions. Extracted frass of fed larvae on semi-artificial diet showed complete oviposition deterrent effect at treatments with 4th, 5th and 6th instars of S. littoralis, also at treatments with 1st–3rd and 6th instars of A. ipsilon, while the same effect was observed when the larvae fed on castor oil leaves as a natural host only at treatment with frass extract of A. ipsilon 6th instar larvae. Presence of low amounts of phenols and flavonoids in water extract of A. ipsilon larval frass resulted in relatively more effect as oviposition deterrent to fertile adult females on treated oviposition sites, while the opposite effect was obtained in S. littoralis larval frass experiments. At semi-field experiments, the percentage reduction of laid eggs reached 100% after two?days at treatments with frass extracts of 4th and 5th S. littoralis larval instars and A. ipsilon 6th instar larvae fed on semi-artificial diet and/or castor oil leaves. Percentage reduction of laid eggs for untreated sacks reached 93.24 and 48.95% after 2 and 30?days, respectively, when placed between treated sacks, in comparison with the mean number of laid eggs for isolated control.     

The effects of host age and superparasitism by the parasitoid, Microplitis rufiventris on the cellular and humoral immune response of Spodoptera littoralis larvae

To study the dynamics of stage-dependent immune responses in Spodoptera littoralis (Boisd.) larvae (Lepidoptera: Noctuidae), single and superparasitism experiments were carried out using the parasitoid Microplitis rufiventris Kok. (Braconidae: Hymenoptera). Compared to younger (preferred) host larvae, the older (non-preferred) host larvae displayed a vigorous humoral response that often damaged and destroyed the single wasp egg or larva. Superparasitism and host age altered both the cellular and humoral immune responses. Younger host larvae showed a stronger encapsulation response compared to older host larvae. Moreover encapsulation rates in younger hosts (e.g., second instar) decreased with increasing numbers of parasitoid eggs deposited/larvae. In older larvae, the encapsulation rate was low in fourth, less in fifth and absent in sixth instar hosts. Conversely, the order and magnitude of the cellular immune response in S. littoralis hosts were highest in second instar larvae with the first instar larvae being a little lower. The immune response steadily decreased from the third through to the fifth instar and was least obvious in the sixth instar. In contrast, the general humoral immune response was most pronounced in sixth instar larvae and diminished towards younger stages. The results suggest that both cellular and humoral responses are stage-dependent. Wasp offspring in younger superparasitized host larvae fought for host supremacy with only one wasp surviving, while supernumerary wasp larvae generally survived in older superparasitized larvae, but were unable to complete development. Older instars seem to have a method for immobilizing/killing wasp larvae that is not operating in the younger instars.     

Bioefficacy of cadmium and lead on cotton leafworm Spodoptera littoralis (Lepidoptera: Noctuidae) larvae

The sensitivity of Spodoptera littoralis second and fourth instar larvae to the heavy metals cadmium (Cd) and lead (Pb) was investigated under laboratory conditions. Both Cd and Pb, even, at very low concentrations, had relatively high toxic effects on S. littoralis larvae. Cd was more toxic to S. littoralis larvae than Pb. In addition, the mean percentage feeding deterrence (FDI%) of Cd and Pb was concentration-dependent. The nutritional indices (consumption index, growth rate, efficiency of converted ingested and digested food, and approximate digestibility) of S. littoralis second and fourth instar larvae were more affected in Cd-treatments compared with those of Pb-treatments. Therefore, the presence of such heavy metals in the environment would exert an adverse impact on S. littoralis larvae and their development.     

Temporal and spatial variation in palatability of soybean and cotton leaves following wounding

Summary Leaves of soybean (Glycine max (L.) Merr.) and cotton (Gossypium hirsutum L.) were mechanically damaged with a single hole and offered to Spodoptera littoralis Boisd (Lep., Noctuidae) larvae in laboratory bioassays at intervals of between 0 and 7 days from damage. The subsequent within-leaf grazing patterns of damaged and undamaged areas were compared using an image-analysing computer, and estimations were made by eye of percentage, areas grazed at three spatial scales. Reduction in palatability of damaged areas of both plant species was detected, at time intervals ranging from 0 to 7 days after damage. This effect was strongest for the longer time intervals and the effect became weaker with increasing distance from the site of damage. These results are discussed in relation to possible defensive roles of wound-induced changes.     

Fitness consequences of cannibalism in the fall armyworm, Spodoptera frugiperda

We investigated the consequences of cannibalism for some correlatesof fitness in the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae).The benefits gained by cannibals were ascertained by comparing survival,development rate, and pupal weight of larvae that had the opportunityto cannibalize with those that did not, at two levels of food availability.Larvae in the cannibalism treatments were provided with a conspecificone instar younger than themselves on five dates throughoutlarval development. Cannibalism was frequent; given the opportunityall larvae predated at least one younger conspecific. The frequencyof cannibalism was not affected by the sex of the cannibal orby the availability of alternative food. However, cannibalssuffered a significant reduction in survival at both high andlow food availability. Furthermore, cannibals had a lower pupal weightin the high food treatment and a reduced development rate inthe low food treatment. The only detectable fitness benefitassociated with cannibalism was a positive correlation betweenthe number of victims consumed and development rate under conditionsof low food availability. On balance, cannibalism appears tobe costly; alternative explanations for its occurrence in thisspecies are discussed.     

Functional response of the spiderChiracanthium mildei [Arachnida: Clubionidae] to prey density

Laboratory experiments demonstrated that the spiderChiracanthium mildei L. Koch. shows a functional response to increasing density of its prey: larvae ofSpodoptera littoralis (Boisd.). A sigmoid curve was found to represent the preying rate.     

A novel tyrosine kinase activity in the cotton leafworm,Spodoptera littoralis

A rapid, highly-specific ELISA for tyrosine kinases readily detects such activity in crude extracts prepared from rat mammary epithelial and fibroblastic cells that have been stimulated with epidermal growth factor or basic fibroblast growth factor. Tyrosine kinase activity is also found in extracts of pupae of the cotton leafworm, Spodoptera littoralis. Both the mammalian and the insect tyrosine kinases are ATP-dependent. Both cytosol and membrane-associated (Triton-X-100-soluble) fractions of Spodoptera littoralis pupae contain tyrosine kinase activity. The growth factor-stimulated tyrosine kinase activities in extracts of growth factor-stimulated rat mammary cells are inhibited by genistein and an analogue of erbstatin: methyl 2,5-dihydroxycinnamate. However, the tyrosine kinase activities present in pupae of Spodoptera littoralis are not sensitive to these inhibitors, suggesting that the major tyrosine kinases of Spodoptera littoralis pupae may be distinct from the growth factor-stimulated mammalian tyrosine kinases.     

Effects of diet on development of Podisus nigrispinus (Dallas) (Het., Pentatomidae), a predator of the cotton leafworm

Abstract:  The effects of diet on development of Podisus nigrispinus (Dallas) (Het., Pentatomidae) were studied at 25°C, relative humidity of 60 ± 10%, and photoperiod of 14 h light : 10 h dark. Development times of P. nigrispinus nymphs were similar when fed with third or fifth instar larvae of cotton leafworm ( Alabama argillacea Hübner) (Lep., Noctuidae) or Tenebrio molitor L. (Col., Tenebrionidae). When fed with housefly larvae ( Musca domestica L.) (Dipt., Muscidae) or artificial diet, the predator had a longer development time. Independent of diet, instar or sex, the females of P. nigrispinus showed a longer longevity than the males. The total survival of the nymphal stage, on the different diets, varied from 22.46 (fed with housefly) to 77.33% (fed with T. molitor larvae). P. nigrispinus males were heavier when fed with third or fifth instar cotton leafworm larvae than when fed with artificial diet. The weight of the females varied from 37.91 (with artificial diet) to 64.68 mg (with fifth instar cotton leafworm larvae). Independently of the diet, newly emerged females of P. nigrispinus were heavier than the males. Females of P. nigrispinus which were fed with fifth instar cotton leafworm larvae had heavier ovaries than those fed other diets.