Anthocoridae Research Articles

Intraguild predation of Orius tristicolor by Geocoris spp. and the paradox of irruptive spider mite dynamics in California cotton

Abstract It is paradoxical when a community of several natural enemies fails to control a pest population when it can be shown experimentally that single members of the natural enemy community are effective control agents when tested individually. This is the case for spider mites, Tetranychus spp., in California cotton. Spider mites exhibit irruptive population dynamics despite that fact that experiments have shown that there are at least four predators ( Galendromus occidentalis , Frankliniella occidentalis , Orius tristicolor , and Geocoris spp.) that, when tested singly, can suppress mite populations. One possible explanation for the paradox is intraguild predation, wherein one predator consumes another. Here, I evaluate the hypothesis that intraguild predation is a strong interaction among spider mite predators. I report manipulative field experiments, focal observations of freely foraging predators in the field, and population survey data that suggest that the minute pirate bug O. tristicolor , is subject to strong predation by other members of the predator community, and in particular by Geocoris spp. These results, combined with the results of prior work, suggest that pervasive intraguild predation among spider mite predators may explain the pest status of Tetranychus spp. in cotton.

The relationship between predator density, community composition, and field predation of Colorado potato beetle eggs

Conservation biological control programs seek to increase natural enemy densities through the adoption of more benign farming practices, under the assumption that higher predator densities will lead to more effective pest suppression. However, predator–predator interference may lead to diminishing returns in improved pest control as predator densities increase. We examined the relationship between predator density and predation rates on Colorado potato beetle eggs in production potato fields. These potato fields naturally spanned a 10-fold range in predator density, due to differences in management practices. Periodically through the growing season we simultaneously measured predator densities and subjected sentinel eggs masses to predation, allowing us to correlate predator density and egg predation for each field on each sample date. Egg predation rates were significantly positively correlated with total predator densities, a correlation that was not improved when predator densities were scaled to reflect differences in feeding rates on potato beetle eggs of the constituent predator taxa. There was no correlation between per-capita egg predation rates and predator density, and so no evidence that predator interference increased with increasing predator density. We divided predators into six dominant taxa—dwarf spiders, crab spiders, minute pirate bugs, big-eyed bugs, damsel bugs, and Lygus bugs (together constituting 93% of all predators collected), and a seventh group, “other predators” that included all other, less common, taxa—and examined correlations between all predator combinations and egg predation rates. The highest correlation was between combined densities of the six most common predator taxa, excluding only the “other predators” grouping. This suggests that predators may be largely equivalent in their impact on Colorado potato beetle eggs, and that field scouts might be able to ignore uncommon predator taxa when sampling for natural enemies.

The Feeding Behavior of the Bigeyed Bug, Minute Pirate Bug, and Pink Spotted Lady Beetle Relative to Main Strawberry Pests

Laboratory assays were performed to determine the impact of three predators, the bigeyed bug, Geocoris punctipes Say, minute pirate bug, Orius insidiosus (Say), and the pink spotted lady beetle, Coleomegilla maculata fuscilabris (Mulsant), on two herbivores, the cotton aphid, Aphis gossypii Glover, and the twospotted spider mite (TSM), Tetranychus urticae Koch, using strawberry (Fragaria ananassa Duchesne) leaflets as a substrate. Both herbivores are considered important strawberry pests worldwide. Daily and hourly consumption of a single prey species studied were conducted as well as a preference for prey test. All stages of the bigeyed bug, minute pirate bug, and pink spotted lady beetle fed on the cotton aphid and TSM. The pink spotted lady beetle had a higher rate of consumption for both the cotton aphid and TSM, and therefore, may be a more effective predator of both prey species. The bigeyed bug and minute pirate bug (third instar and adult) prefer TSM over cotton aphids based on handling time. In contrast, the pink spotted lady beetle (third instar and adult) prefers aphids over mites. Results from these experiments indicated that the pink spotted lady beetle seems to be a good predator to incorporate into an existing biological control program for cotton aphid and TSM on strawberries. Better understanding of these three predators will lead to their more efficient use for biological control of aphids and TSM.

Survival of stored-product insect natural enemies in spinosad-treated wheat.

The survival of stored product insect natural enemies in wheat treated with spinosad was investigated in laboratory and pilot scale experiments. The predator Xylocoris flavipes (Reuter), the warehouse pirate bug, and the parasitoids Habrobracon hebetor (Say), Theocolax elegans (Westwood), and Anisopteromalus calandrae (Howard) were exposed to wheat treated with aliquots of water or spinosad at 0.05-1 mg ([AI])/kg. X. flavipes was the only species that survived (92% survival) in spinosad-treated wheat at 1 mg/kg. X. flavipes suppressed populations of immature Tribolium castaneum (Herbst), the red flour beetle, by nearly 90% compared with a water-treated control, but 100% suppression of immatures was achieved in wheat receiving spinosad or spinosad + X. flavipes treatments. A 3-mo pilot scale experiment to evaluate T. castaneum suppression in drums holding 163.3 kg of wheat showed that the pest populations increased throughout the study in the control treatment, but peaked after 1 mo in the X. flavipes-treated drums. By comparison, better T. castaneum population suppression was achieved in spinosad or spinosad + X. flavipes treatments. Although X. flavipes can survive and reproduce in spinosad-treated wheat, under our test conditions spinosad alone provided adequate suppression of T. castaneum populations in stored wheat.

Survival of Stored-Product Insect Natural Enemies in Spinosad-Treated Wheat

The survival of stored product insect natural enemies in wheat treated with spinosad was investigated in laboratory and pilot scale experiments. The predator Xylocoris flavipes (Reuter), the warehouse pirate bug, and the parasitoids Habrobracon hebetor (Say), Theocolax elegans (Westwood), and Anisopteromalus calandrae (Howard) were exposed to wheat treated with aliquots of water or spinosad at 0.05–1 mg ([AI])/kg. X. flavipes was the only species that survived (92% survival) in spinosad-treated wheat at 1 mg/kg. X. flavipes suppressed populations of immature Tribolium castaneum (Herbst), the red flour beetle, by nearly 90% compared with a water-treated control, but 100% suppression of immatures was achieved in wheat receiving spinosad or spinosad + X. flavipes treatments. A 3-mo pilot scale experiment to evaluate T. castaneum suppression in drums holding 163.3 kg of wheat showed that the pest populations increased throughout the study in the control treatment, but peaked after 1 mo in the X. flavipes-treated drums. By comparison, better T. castaneum population suppression was achieved in spinosad or spinosad + X. flavipes treatments. Although X. flavipes can survive and reproduce in spinosad-treated wheat, under our test conditions spinosad alone provided adequate suppression of T. castaneum populations in stored wheat.

Comparison of prey-derived and non-insect supplements on egg-laying of Orius insidiosus maintained on artificial diet as adults

The effects of proteins and lipids from insect- and non-insect sources on the oviposition rate of the insidious flower bug, Orius insidiosus (Say) fed supplemented artificial diets were evaluated. Soluble proteins were isolated from Plodia interpunctella (Hübner) eggs, desalted by column chromatography, lyophilized, and tested as a diet supplement. A total lipid extract from P. interpunctella eggs was also evaluated as a diet supplement, and the three most abundant fatty acids (palmitic, linoleic, and oleic acid) identified in the extract were tested as a combined supplement. Non-insect supplements evaluated in diet were bovine serum albumin, chicken liver, beef liver, and chicken egg albumin. O. insidiosus were fed the supplemented diets, whole P. interpunctella eggs, or unsupplemented artificial diet, and the mean total numbers of eggs oviposited per female were recorded throughout adult life. The Plodia egg proteins significantly increased egg production and mean number of oviposition days at concentrations of protein that were 83-, 557-, and 837-fold lower than the concentrations needed for beef liver, bovine serum albumin, and chicken egg albumin, respectively. We conclude that soluble proteins from P. interpunctella eggs provided superior nutritional value for reproduction in female O. insidiosus . Additional information is required to explain the higher specific activity of soluble egg proteins compared to the specific activities of the non-insect proteins. However, we speculate that the quality of egg proteins or of an unknown substance bound to the proteins may be important for reproduction in this predator.

Increased egg-laying in Orius insidiosus (Hemiptera: Anthocoridae) fed artificial diet supplemented with an embryonic cell line

The insidious flower bug, Orius insidiosus (Say) (Hemiptera: Anthocoridae), can be reared on an artificial diet absent of insect components, but yolk production is reduced and resultant rates of oviposition and egg production are poor. Supplementing the artificial diet with cells from an embryonic cell line, IPLB-(PiE) of Plodia interpunctella (Hübner), enhanced oviposition rates. Ovipositional rates were evaluated using a short 7-day bioassay. Cells were separated from Grace’s medium containing 10% fetal bovine serum, washed several times in Grace’s medium alone, and then homogenized before they were incorporated into the diet. In addition to the cell-supplemented diet, several control diets were also tested: diet supplemented with Grace’s medium alone, Grace’s medium with fetal bovine serum, and conditioned Grace’s medium (i.e., the medium the cells were cultured in). Adult predators were placed on the diets the third day after eclosion and allowed to feed for 6 days and provided with an oviposition substrate for 24 h on day 7. Egg production was significantly increased only in the cell-supplemented diet, a similar result that occurred when cumulative egg production was recorded during the life span of the females. Oviposition increased incrementally with the increase in concentration of cells added to the diet and was significantly better than control diet at 0.25 ml homogenized cells/1.2 ml diet (1.123 × 10 5 cells, 31 μg protein) to 1.0 ml cells/1.2 ml diet (1.86 × 10 6 cells, 124 μg protein). Although the cell line enhanced the rate of oviposition at a relatively low concentration of protein, we do not know if the protein or some other nutritional components of the cells were responsible for the increased oviposition rate. The cell line may be used to directly supplement the described diet for O. insidiosus and/or serve as a source of material that could simplify purification and identification of the cell component(s) responsible for stimulating oviposition. Additionally, the 7-day bioassay may be used to expedite identification of active fractions during chemical analysis of the cell line.

Effect of the red imported fire ant on cotton aphid population density and predation of bollworm and beet armyworm eggs.

The effects of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), on cotton aphid, Aphis gossypii Glover, populations and its predation of bollworm, Helicoverpa zea (Boddie), and beet armyworm, Spodoptera exigua (Hübner), (both Lepidoptera: Noctuidae) eggs were evaluated in cotton under field conditions during 2001 and 2002 in central and northern Texas. In central Texas, cotton aphid populations were approximately 5.5 times greater and predation of sentinel bollworm eggs 2 times greater in the presence of S. invicta versus in its absence, although aphid populations did not reach economic levels. Most predation of beet armyworm egg masses, measured via direct nocturnal observations, was due to S. invicta (68%) and cotton fleahopper, Pseudatomoscelis seriatus (Reuter) (21%), where S. invicta was present, and by the mite Abrolophus sp. (52%), spiders (13%), and minute pirate bug (Orius sp.) (13%) where S. invicta was absent. Predation of sentinel bollworm eggs and beet armyworm egg masses was approximately 1.5 and 4.1 times greater, respectively, in the presence of S. invicta versus in their absence. In the presence of S. invicta, the relative frequencies of minute pirate bug and cotton fleahopper were higher, and of S. invicta and native ants lower in beat bucket samples compared with their relative frequencies in nocturnal observations of predation upon beet armyworm egg masses. In the absence of S. invicta seven of eight predators sampled were similarly represented in beat bucket samples and nocturnal observations of beet armyworm egg mass predation, whereas minute pirate bug occurred at a higher frequency in beat bucket samples relative to nocturnal observations. These observations suggested that the relative frequencies of minute pirate bug, cotton fleahopper, S. invicta and native ants in beat bucket samples do not closely reflect the frequency with which these predators prey on noctuid eggs. Overall, the results of this study show that although S. invicta may promote aphid populations early in the growing season, it is an important predator of bollworm and beet armyworm eggs later in the season.

Effect of the Red Imported Fire Ant on Cotton Aphid Population Density and Predation of Bollworm and Beet Armyworm Eggs

The effects of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), on cotton aphid, Aphis gossypii Glover, populations and its predation of bollworm, Helicoverpa zea (Boddie), and beet armyworm, Spodoptera exigua (Hübner), (both Lepidoptera: Noctuidae) eggs were evaluated in cotton under field conditions during 2001 and 2002 in central and northern Texas. In central Texas, cotton aphid populations were ≈5.5 times greater and predation of sentinel bollworm eggs 2 times greater in the presence of S. invicta versus in its absence, although aphid populations did not reach economic levels. Most predation of beet armyworm egg masses, measured via direct nocturnal observations, was due to S. invicta (68%) and cotton fleahopper, Pseudatomoscelis seriatus (Reuter) (21%), where S. invicta was present, and by the mite Abrolophus sp. (52%), spiders (13%), and minute pirate bug (Orius sp.) (13%) where S. invicta was absent. Predation of sentinel bollworm eggs and beet armyworm egg masses was ≈1.5 and 4.1 times greater, respectively, in the presence of S. invicta versus in their absence. In the presence of S. invicta, the relative frequencies of minute pirate bug and cotton fleahopper were higher, and of S. invicta and native ants lower in beat bucket samples compared with their relative frequencies in nocturnal observations of predation upon beet armyworm egg masses. In the absence of S. invicta seven of eight predators sampled were similarly represented in beat bucket samples and nocturnal observations of beet armyworm egg mass predation, whereas minute pirate bug occurred at a higher frequency in beat bucket samples relative to nocturnal observations. These observations suggested that the relative frequencies of minute pirate bug, cotton fleahopper, S. invicta and native ants in beat bucket samples do not closely reflect the frequency with which these predators prey on noctuid eggs. Overall, the results of this study show that although S. invicta may promote aphid populations early in the growing season, it is an important predator of bollworm and beet armyworm eggs later in the season.

Monitoring and Trapping Insects on Poinsettia with Yellow Sticky Card Traps Equipped with Light-emitting Diodes

Insects in a commercial poinsettia (Euphorbia pulcherrima) greenhouse were monitored with yellow sticky card (YC) traps and YC equipped with 530-nm lime green light-emitting diodes (LED-YC) traps from 3 June to 25 Nov. 2002. Pest insects were: dark-winged fungus gnat (Bradysia coprophila), sweet potato whitefly (Bemisia tabaci) biotype B (= B. argentifolii), western flower thrips (Frankliniella occidentalis) and leafhopper (Empoasca sp.). Natural enemies were: minute pirate bug (Orius tristicolor), parasitic wasps (Hymenoptera), and rove beetles (Staphylinidae). Over the 24 weeks of the experiment, LED-YC traps captured more dark-winged fungus gnats, sweet potato whiteflies, leafhoppers, and rove beetles compared with YC traps. Capture of western flower thrips, minute pirate bugs, and parasitic wasps were not significantly increased on the YC traps equipped with LEDs. The results indicate that the LED-YC traps attract three major pest insects in poinsettia greenhouses and do not catch more beneficial, minute pirate bugs and parasitic wasps, but may catch significant number of rove beetles. The results suggest that LED-YC traps may be useful to monitor and reduce pest populations in greenhouses.

Discrimination among Japanese Species of the Orius Flower Bugs (Heteroptera: Anthocoridae) Based on PCR-RFLP of the Nuclear and Mitochondrial DNAs

A PCR-RFLP-based method of species identification was considered for 5 Japanese species of Orius Wolff flower bugs, Orius strigicollis (Poppius), O. minutus (Linnaeus), O. sauteri (Poppius), O. nagaii Yasunaga, and O. tantillus (Motschulsky). Nucleotide sequences of the internal transcribed spacer 1 of the nuclear ribosomal gene and a portion of mitochondrial cytochrome oxidase subunit I gene were compared among species and recognition sites of diagnostically useful restriction enzymes were examined. The PCR-RFLP analysis using 108 individuals of 26 laboratory strains confirmed that the 5 species could be correctly identified by banding patterns generated using these DNA regions. Because our PCR primers can amplify DNA fragments from DNA template extracted from both freshly killed insects and dried specimens stored at room conditions, the PCR-RFLP-based method was considered useful for analyses of field populations in which researchers store and accumulate field-collected samples before they perform laboratory examinations.

Orius insidiosus (Say, 1832) (Heteroptera, Anthocoridae): sensibilidade ao fotoperíodo e diapausa reprodutiva?

The minute pirate bugs, Orius spp., are known as predators on several pests as thrips, aphids, spider mites and whiteflies. Orius insidiosus is an important thrips predator, commercially used around the world. However, one of the main problems on biological control of thrips in temperate regions is the occurrence of reproductive diapause in Orius species. This characteristic promotes the interruption of biological control strategies when predators are exposed to short photoperiods. This research had as objective to evaluate the influence of different photoperiod conditions on eggs/nymphs and adults of O. insidiosus in laboratory. The trials were carried out through the combination of eggs/nymphs and adults reared under the photoperiods 10L:14D; 11L:13D; 12L:12D and 13L:11D, at 25±2oC and 70±10% RH. The predators were maintained during their pre-imaginal development time under one of the photoperiods and, after being emerged as adults transferred to another photoperiod regime. The predator had a tendency to present longer development time under photoperiod 13L:11D. There was no influence of the different photoperiods conditions on the reproduction of O. insidiosus. The females laid eggs normally during all their lifetime. O. insidiosus is not sensitive to photoperiod evaluated and do not enter in reproductive diapause.

Japanese species of the genus Amphiareus Distant (Heteroptera: Anthocoridae), with descriptions of two new species

AbstractJapanese species of the genus Amphiareus Distant of the lyctocorine flower bug are revised. Two new species, A. ruficollaris and A. ochraceus, are described and illustrated, and descriptions of three known species, A. constrictus (Stål), A. morimotoi (Hiura) and A. obscuriceps (Poppius), are revised. A key is provided to distinguish the Japanese species.

Kairomonal attraction of predatory bugs (Heteroptera: Anthocoridae) and brown lacewings (Neuroptera: Hemerobiidae) to sex pheromones of Matsucoccus species (Hemiptera: Matsucoccidae)

Abstract The kairomonal response of potential predators of pine bast scales Matsucoccus Cockerell was investigated using traps baited with female sex pheromones of Matsucoccus josephi Bodenheimer and Harpaz, Matsucoccus feytaudi Ducasse, and Matsucoccus matsumurae Kuwana. In addition to the attraction of conspecific males and a weak cross attraction of congener ones, two guilds of predators were attracted: flower bugs of the genus Elatophilus Reuter and brown lacewings of the genera Hemerobius L. and Sympherobius Banks. Elatophilus hebraicus Pericart, Elatophilus nigricornis Zetterstedt, Elatophilus crassicornis Reuter, Hemerobius stigma Stephens, and Sympherobius fuscescens (Wallengern) were captured in the West Palearctic region, whereas Elatophilus inimica Drake & Harris, H. stigma, and Hemerobius stigmaterus Fitch were captured in the US. E. hebraicus alone was attracted to all three pheromones, while all other species responded to one or two of the them. The Matsucoccus pheromones are ketones, sharing a common chiral ketodiene moiety. The capture pattern of both predator guilds points to a general mode of kairomonal response with some specificity due to differences in the second side chain of these pheromones. Our findings suggest that further application of Matsucoccus pheromone traps may reveal additional predators which could be used as biological control agents of the noxious pine bast scale species.

Development of a bioassay system for the predator, Xylocoris flavipes (Heteroptera: Anthocoridae), and its use in subchronic toxicity/pathogenicity studies of Beauveria bassiana strain GHA.

Microbial biocontrol agents are useful commercially only if they do not harm other natural biocontrol organisms, at recommended use rate in the environment where the microorganism is being used. To test the hypothesis that the predatory warehouse pirate bug, Xylocoris flavipes (Reuter), is not adversely affected by the entomopathogen, Beauveria bassiana (Balsamo) Vuillemin strain GHA, we developed a method using individually confined bugs during a 10-d feeding regime. Three concentrations of a conidial suspension were applied to assay surfaces (filter paper disks) to achieve 2.7 x 10(7), 2.6 x 10(6), and 2.6 x 10(5) conidia per cm2, representing 100X, 10X, and a field rate of 2.6 x 10(13) conidia per ha (+/-10%), respectively. Fifth instar X. flavipes suffered 0% infection at the field rate when confined to treated filter paper for 10 d (16% and 42% infection, respectively, at 10X and 100X the field rate). Second instar migratory grasshoppers, Melanoplus sanguinipes (F.), exposed to the same doses suffered 97, 92, and 100% mortality at the three respective doses 10 d after exposure. These data indicate that B. bassiana can be used safely at recommended application levels without significant effect on fifth instar populations of X. flavipes.

Effects of Various Insecticide Residues in Cotton on Gender and Developmental Stage of the Insidious Flower Bug (Hemiptera: Anthocoridae)

Orius insidiosus (Say) is an important predator of several economic pests in cotton. Laboratory-reared males, females and third-instar nymphs were exposed to field residues of nine insecticides applied to cotton plants. Insects were caged for 24 h and then removed to determine mortality from 0, 1, 2, 3, and 7-day-old insecticide residues. Insecticides and rates (kg ai/ha) tested were spinosad (0.09, 0.199), indoxacarb (0.78, 0.123), imidacloprid (0.027, 0.053), tebufenozide (0.14, 0.28), methoxyfenozide (0.28, 0.84), abamectin (0.01, 0.02), emamectin benzoate (0.005, 0.01), fipronil (0.042, 0.056), and λ-cyhalothrin (0.014, 0.028). Fipronil and λ-cyhalothrin were the most toxic, causing a significant reduction in survival (up to 3-day-old residues). Abamectin and emamectin benzoate caused significant mortality in predators exposed shortly after application, but survival tended to increase as residues aged. Imidacloprid and indoxacarb were intermediate, causing approximately 50% mortality in this insect. Survival was good in all treatments with 7-day-old residues with the exception of λ-cyhalothrin. Males tended to by more sensitive with lower survival than females.

Toxicity of fruit fly baits to beneficial insects in citrus

Two fruit fly baits, Nu-Lure/malathion and GF-120 (Spinosad) were evaluated in the laboratory for non-target impacts on beneficial insects. Nu-Lure/malathion proved attractive and toxic to adults and larvae of the coccinellid species, Curinus coeruleus Mulsant, Cycloneda sanguinea L. and Harmonia axyridis Pallas, a lacewing species, Chrysoperla rufilabris Burmeister. The coccinellids Olla v-nigrum Mulsant, Scymnus sp. and nymphs of the insidious flower bug, Orius insidiosus (Say) did not succumb to Nu-Lure baits, even in no-choice situations. Nu-Lure was also attractive and lethal to adults of two aphidophagous flies; Leucopis sp. and the syrphid fly Pseudodorus clavatus (F.). Both Nu-Lure and GF-120 caused significant mortality to the parasitoid wasps, Aphytis melinus De Bach and Lysiphlebus testaceipes Cresson, within 24 h of exposure. However, GF-120 caused no significant mortality to any coccinellid in either choice or no-choice situations, despite considerable consumption of baits. Adults of P. clavatus tended to avoid GF-120, although mortality was significant in no-choice tests. Although larvae and adults of the lacewing C. rufilabris consumed GF-120, mortality was delayed; adults died 48 -96 h post-exposure and those exposed as larvae died two weeks later in the pupal stage. The Nu-Lure bait did not appear palatable to any of the insects, but the high concentration of malathion (195,000 ppm) caused rapid mortality to susceptible insects. Nu-Lure bait without malathion also caused significant mortality to flies and lacewings in cage trials. Although GF-120 bait appeared more benign overall, further research efforts are warranted to increase its selectivity for target fly species and reduce its attractiveness to parasitoids and lacewings. I conclude that the Florida "fly free zone" protocol in its current form is not compatible with an IPM approach to commercial citrus production.

Intraguild Predation of Beneficial Arthropods by Red Imported Fire Ants in Cotton

The red imported fire ant, Solenopsis invicta (Buren), is an invasive species in the southern United States and is expanding its range westward to California and eastward up the Atlantic Coast. This voracious predator can reach extremely high densities and have widespread effects once it invades an ecosystem. We conducted a 2-yr sampling study and a series of greenhouse and field experiments to document the impact of red imported fire ants on beneficial insects in cotton. We found that the densities of 12 of 13 natural enemies sampled on cotton plants in 1999, and 8 out of 8 sampled in 2000, were negatively correlated with the densities of foraging fire ant workers. Red imported fire ants reduced the survival of lady beetles (Coccinella septempunctata L., and Hippodamia convergens Guerin-Meneville) (Coleoptera: Coccinellidae) by 50% and green lacewing larvae (Chrysoperla carnea Stephens) (Neuroptera: Chrysopidae) by 38% in greenhouse experiments. Fire ants did not, however, reduce the survival of spiders (Oxyopidae, Thomisidae, and Clubionidae). We used a commercially available fire ant bait to suppress fire ant populations in cotton fields during the 2000 growing season and compared the densities of beneficial arthropods in treated versus control fields. Densities of lady beetles, spiders, and big-eyed bugs (Heteroptera: Geocoridae) were significantly higher in fields with suppressed fire ant populations than in fields with relatively large fire ant populations. The effect of fire ants on minute pirate bugs (Heteroptera: Anthocoridae) was inconsistent, and populations of damsel bugs (Heteroptera: Nabidae) and hooded beetles (Coleoptera: Anthicidae) were not affected by fire ant suppression. The results of this study suggest that red imported fire ants are major intraguild predators of important beneficial arthropods in cotton.

Effects of starvation on the search path characteristics of Orius majusculus (Reuter) (Het., Anthocoridae)

Abstract: Orius majusculus (Reuter) is a polyphagous predator bug used to control western flower thrips Frankliniella occidentalis (Pergande). As physiological factors may be highly influential upon the predatory behaviour of Orius spp. we studied the possible impact of starvation on the search path of this bug. Orius majusculus was maintained on a diet of Ephestia kuehniella Zeller (Lep., Pyralidae) eggs in laboratory. Adults were collected immediately after the imaginal moult and were individually placed in Petri dishes with abundant food. Each adult was randomly assigned to one of the following five treatments: immediate observation or starved for 2, 6, 9 or 12 h prior to observation. The observation procedure consisted of placing a single O. majusculus adult at the centre of an empty arena. The displacement of each insect was recorded with a video camera until it had reached the limits of the arena. The recorded paths were digitized and the digitized search path was used to calculate the mean walking speed, the number of stops per second, the duration of stops and the diffusion rate. The results clearly show that, in comparison with unstarved bugs, insects that experienced 6 h of prey deprivation walked more slowly, stopped more frequently and for longer periods, and had a lower rate of diffusion away from the release point. In contrast, all search path variables returned to the levels measured in unstarved bugs in the group that experienced the longest period of starvation (12 h), whereas groups of O. majusculus that had experienced 2 or 9 h of prey deprivation presented intermediate values for all the variables tested. Starvation produced evident changes in the search path characteristics that we assume to be related to physiological states of hunger and energy availability. These behavioural changes related to physiological state could have consequences for the use of this pirate bug in biological control.

Functional Response ofXylocoris flavipes(Hemiptera: Anthocoridae) - Effects of Prey Species and Habitat

Abstract Xylocoris flavipes (Reuter), the warehouse pirate bug, is a predator of many stored-products pests. This study compared the functional response of X. flavipes with different densities of the prey species Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.), Plodia interpunctella (Hubner), and Rhyzopertha dominica (F.) in two different habitats: empty glass jars and glass jars filled with wheat kernels that were designed to simulate more natural conditions in stored grain. Differences in the functional response of X. flavipes to all combinations of prey densities and grain conditions were compared with the predicted functional response curves from Holling’s type I and type II models, and to Hassell’s type III model. The functional response of X. flavipes was best described by Holling’s type II model, but a type III response occurred with prey that were more difficult to subdue, such as T. castaneum larvae. Numbers of prey attacked by females were greater than those attacked by males (P < 0...