Francisco S. Ramalho

Effect of feeding on three Eucalyptus species on the development of Brontocoris tabidus (Het.: Pentatomidae) fed with Tenebrio molitor (Col.: Tenebrionidae).

Brontocoris tabidus (Heteroptera: Pentatomidae) is an important predator of defoliating Lepidoptera in Brazil, which has been mass produced and released against defoliating caterpillars in Eucalyptus plantations. We aimed to improve the mass production of this predator by providing eucalypt seedlings, in addition to an alternative prey, for its development. The effect of three Eucalyptus species on the development of B. tabidus fed with Tenebrio molitor L. (Coleoptera: Tenebrionidae) pupae, was studied at a temperature of 25.0 - 2.5 o C; a relative humidity of 70.0 - 10.0% and a photophase of 12:12 hours (light:dark). Pupae of T. molitor were provided in each of the following feeding treatments: treatment 1, Eucalyptus urophylla seedlings; treatment 2, Eucalyptus camaldulensis seedlings; treatment 3, Eucalyptus grandis seedlings; and treatment 4, no seedling (only pupae of T. molitor ). Duration of the nymphal phase of the predator was similar in all treatments with plant and prey. It was observed that adults developed from nymphs fed on T. molitor only, had deformed wings and a small abdomen. B. tabidus fed during their nymphal and adult stages with prey together with Eucalyptus seedlings, had improved longevity, higher egg viability and a larger number of eggs and nymphs, than those insects fed only with prey. Therefore, it seems advisable to rear B. tabidus with prey and seedlings of Eucalyptus species, to improve the mass production of this predator for biological control of defoliating caterpillars of eucalypt plantations.

Ultrastructure of the Digestive Cells in the Midgut of the Predator Brontocoris tabidus (Heteroptera: Pentatomidae) after Different Feeding Periods on Prey and Plants

ABSTRACT Brontocoris tabidus (Signoret) (Heteroptera: Pentatomidae) is an obligate zoophytophagous predator because its population can be maintained in the laboratory when fed on both prey and plants. We evaluated ultrastructural changes in the midgut digestive cells of adult B. tabidus, subjected to different treatments (starvation or feeding on plant material and prey) for different periods. Their midguts were dissected, divided into anterior, medium and posterior sections, processed, and analyzed with light and transmission electron microscopy. The anterior region of the midgut of B. tabidus, starved or fed on eucalyptus leaves, contained no glycogen. B. tabidus fed on plant material showed multivesicular bodies in this region, and spherocrystals after 6 h of feeding on prey. The microvilli of the medium midgut were longer than those of the anterior and posterior midgut. The posterior midgut differed from the other two regions by an abundance of mitochondria, rough endoplasmatic reticulum and double membrane vesicles in the apical region, 6 h after feeding. The ultrastructural features of the digestive cells in the anterior, medium and posterior regions of the midgut suggest that they play a role in digestive enzyme synthesis, ion and nutrient absorption, and storage and excretion of substances.

Midgut morphology and enzymes of the obligate zoophytophagous stinkbug Brontocoris tabidus (Signoret, 1863) (Heteroptera: Pentatomidae)

The predatory bug, Brontocoris tabidus (Signoret, 1863), is an obligate zoophytophagous species; it cannot survive for long periods in the absence of plant resources. Understanding its digestive process will help elucidate the ecological and economical significance of this species. This is a study of the morphology and enzymes of the midgut of B. tabidus. The midgut is divided into four distinct regions like other heteropteran insects. In the anterior region, digestive cells are columnar with dilated apices containing unstained granules that contain some Fe and Ca accumulations; a short brush border is evident. In the central region of the midgut, digestive cells contain many cytoplasmic granules with many Fe and Ca. In this region there is a short brush border and the dilated cell apices seem to discharge into the midgut lumen. In the posterior region of the midgut, the cells are cubic and contain few cytoplasmic granules that contain low amount of Ca and Fe. At the end of the midgut is a midgut-hindgut transitional region. Biochemical analyses showed the presence of a trypsin-like enzyme, amylase and lipase in all three midgut regions. These are discussed in relation to the feeding habits and evolution of the Hemiptera.

Ultrastructure and heteromorphism of spermatozoa in five species of bugs (Pentatomidae: Heteroptera)

Pentatomidae is one of the largest Heteroptera families, comprising about 10% of the species estimated for the suborder. In spite of existing studies, doubts remain regarding the systematics of Pentatomomorpha. In this study, five species of Pentatomidae spermatozoa were examined to achieve characteristics that enable inferences in the phylogeny of the group and in behavioral issues associated with the presence of polymorphisms. Spermatozoa polymorphisms, characterized by two classes of sizes, are found in Podisus nigrispinus, Podisus distinctus, and Brontocoris tabidus, whereas Thynacanta marginata (Dallas) and Supputius cincticeps have single-size spermatozoa. The head region consists of an acrosome, a nucleus, and part of the centriolar adjunct. In the more anterior region, the nucleus is parallel to the centriolar adjunct. In the nucleus-flagellum transition region, the nucleus overlaps the anterior region of the mitochondrial derivatives, just above the axoneme. The mitochondrial derivatives and the axoneme run the entire extent of the flagellum. In species in which the spermatozoa are polymorphic, the larger spermatozoa have derivatives mitochondrial approximately 3-fold larger than the smaller spermatozoa. Characteristics derived from the morphology of spermatozoa indicate synapomorphies and are promising for systematic studies.

Estimative of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) development time with non linear models

The objective of this study was to evaluate the precision of the non linear models of Davidson (1942, 1944), Stinner et al. (1974), Sharpe & DeMichele (1977), and Lactin et al. (1995) to describe relationship between developmental rate of different stages of Podisus nigrispinus (Dallas) and temperature. Lower values of R2 for the models of Davidson (0.1593 to 0.2672, and 0.1406 to 0.2804 for males and females, respectively) and of Stinner et al. (0.2136 to 0.6389, and 0.1417 to 0.3045 for males and females, respectively) showed that these models were not adequate to estimate developmental rate of P. nigrispinus as function of temperature. However, high values of R2 for the models of Sharpe & DeMichele (0.9226 to 0.9893, and 0.8818 to 0.9914 for males and females, respectively), and of Lactin et al. (0.9485 to 0.9997, and 0.8961 to 0.9997 for males and females, respectively) showed that these models are suitable to estimate developmental rate of P. nigrispinus as function of temperature. Females of P. nigrispinus showed high tolerance to high temperature which is represented by high values of HH for immature stage of this insect obtained with the Sharpe & DeMichele model. According to this model females of P. nigrispinus present thermal stress at 33.3oC, which indicates that maximum thermal estimated by this model was close to the real one.

The Biology and Thermal Requirements of the Fennel Aphid Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae)

The relationship between the insect development rate and temperature was established very early and represents an important ecological variable for modeling the population dynamics of insects. The accurate determination of thermal constant values and the lower and upper developmental thresholds of Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae) on fennel (Foeniculum vulgare Miller (Apiales: Apiaceae)) crops would obviously benefit the effective application of control measures. This paper is a study of the biology and thermal requirements of H. foeniculi. Winged insects were collected from fennel crops at the Embrapa Algodão in Campina Grande, Paraíba. Nymphs (age ≤24 h) produced by winged insects were subjected to constant temperatures of 15, 20, 25, 28, 30 or 33°C, a photophase of 12 h and a relative humidity of 70±10%. The results of the study showed that at temperatures between 15 and 30°C, H. foeniculi nymphs were able to develop normally. The four instars were found at all temperatures tested. However, temperatures of 3 and 33°C were lethal to the nymphs. The nymph stage development time varied from 5 (30°C) to 19 (15°C) days. The influence of temperature on the development time is dependent on the instar. The base temperature (Tb) and the thermal constant (K) for the nymph stage were estimated at 11.2°C and 107.5 degree-days, respectively. The shortest nymph development stage was observed at 30°C, and the highest nymph viability (85.0%) was observed at 28°C. This information can be used for developing phenological models based on the temperature and development rate relationships so that outbreaks of H. foeniculi in the fennel crop can be predicted, therefore improving the application of control programs targeting this fennel pest.

Feeding of fall armyworm, Spodoptera frugiperda, on Bt transgenic cotton and its isoline

Studies on insect food intake and utilization are important for determining the degree of insect/plant association and host species’ resistance, and also for helping design pest management programs by providing estimates of potential economic losses, techniques for mass breeding of insects, and identifying physiological differences between species. We studied the feeding and development of fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), on transgenic (Bt) and non‐transgenic (non‐Bt) cotton. The larvae of S. frugiperda fed on Bt cotton had a longer development period (23.0 days) than those fed on non‐Bt cotton (20.2 days). Survivorship of S. frugiperda larvae fed on Bt cotton (74.1%) was lower than that of larvae fed on non‐Bt cotton (96.7%). Pupal weight of larvae fed on Bt cotton (0.042 g) was lower than that of larvae fed on non‐Bt cotton (0.061 g). The cotton cultivar significantly affected food intake, feces production, metabolization, and food assimilation by S. frugiperda larvae. However, it did not affect their weight gain. Intake of Bt‐cotton leaf (0.53 g dry weight) per S. frugiperda larva was lower than the intake of non‐Bt‐cotton leaf (0.61 g dry weight). Larvae fed on Bt‐cotton leaves produced less feces (0.25 g dry weight) than those fed on non‐Bt‐cotton leaves (0.37 g dry weight). Weight gain per S. frugiperda larva fed on Bt‐cotton leaves (0.058 g dry weight) was similar to the weight gain for larvae fed on non‐Bt‐cotton leaves (0.056 g dry weight). The cotton cultivar significantly affected the relative growth, consumption, and metabolic rates, as well as other nutritional indices: the figures were lower for larvae fed on Bt‐cotton leaves than for larvae fed on non‐transgenic cotton leaves.

Mortality of the defoliator Euselasia eucerus (Lepidoptera: Riodinidae) by biotic factors in an Eucalyptus urophylla plantation in Minas Gerais State, Brazil

Euselasia eucerus (Hewitson, 1872) (Lepidoptera: Riodinidae) is a Brazilian native species commonly found in Eucalyptus plantations. Biotic mortality factors of this defoliator were studied in a Eucalyptus urophylla plantation in Minas Gerais State, Brazil aiming to identify natural enemies and their impact on this insect. Euselasia eucerus had biotic mortality factors during all development stages. The most important were Trichogramma maxacalii Voegelé and Pointel, 1980 (Hymenoptera: Trichogrammatidae) during egg stage (48.9%), a tachinid fly (Diptera: Tachinidae) during larval stages (10%) and Itoplectis sp. (Hymenoptera: Ichneumonidae) during pupal stage (52.2%). The parasitism rate was higher in the basal part of the plant canopy (37.8%).

Toxic effects of the neem oil (Azadirachta indica) formulation on the stink bug predator, Podisus nigrispinus (Heteroptera: Pentatomidae).

This research investigated the effects of neem oil on mortality, survival and malformations of the non-target stink bug predator, Podisus nigrispinus. Neurotoxic and growth inhibitor insecticides were used to compare the lethal and sublethal effects from neem oil on this predator. Six concentrations of neem oil were topically applied onto nymphs and adults of this predator. The mortality rates of third, fourth, and fifth instar nymphs increased with increasing neem oil concentrations, suggesting low toxicity to P. nigrispinus nymphs. Mortality of adults was low, but with sublethal effects of neem products on this predator. The developmental rate of P. nigrispinus decreased with increasing neem oil concentrations. Longevity of fourth instar nymphs varied from 3.74 to 3.05 d, fifth instar from 5.94 to 4.07 d and adult from 16.5 and 15.7 d with 0.5 and 50% neem doses. Podisus nigrispinus presented malformations and increase with neem oil concentrations. The main malformations occur in wings, scutellum and legs of this predator. The neem oil at high and sub lethal doses cause mortality, inhibits growth and survival and results in anomalies on wings and legs of the non-traget predator P. nigrispinus indicating that its use associated with biological control should be carefully evaluated.

Diet affects reproduction and number of oocytes per ovary of the predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae)

The effect of the type of diet consumed on the reproduction of Podisus nigrispinus (Dallas) was studied. Females of P. nigrispinus fed on an artificial diet had a longer preoviposition period than those fed on 3rd or 5th instar cotton leafworm larvae [Alabama argillacea (Hubner)] or mealworm (Tenebrio molitor L.) larvae. P. nigrispinus females fed on 3rd or 5th instar cotton leafworm larvae or mealworm larvae had a longer oviposition period than females on an artificial diet. The numbers of egg masses per female and of egg masses per female per day were higher when P. nigrispinus was fed on 3rd or 5th instar cotton leafworm larvae than when fed on an artificial diet. Podisus nigrispinus females fed on 5th instar cotton leafworm larvae produced a greater number of eggs per female, eggs per egg mass, and eggs per female per day, had a higher nymphal hatch rate than those fed other diets and had higher numbers of oocytes per central ovariole or per ovary than those fed on 3rd instar cotton leafworm larvae, artificial diet, house fly (Musca domestica L.) larvae or mealworm larvae.