Efficiency of four heteroptera as predators ofAphis gossypii andMacrosiphum euphorbiae (Hom.: Aphididae)

Predation rate and nymphal development time were determined for four predatory bugs (Dicyphus tamaninii Wagner andMacrolophus caliginosus Wagner [Het.:Miridae],Orius laevigatus (Fieber) andO. majusculus (Reuter) [Het.:Anthocoridae], on cucumber withAphis gossypii Glover (Hom.:APhididae) as prey and for both mirids also on tomato withMacrosiphum euphorbiae (Thomas) as prey. All four predator species were able to achieve adulthood feeding on both aphids. The developmental period ofD. tamaninii nymphs was the longest and the shortest was forO. majusculus. During nymphal developmentD. tamaninii consumed greater numbers of both aphids thanM. caliginosus, whileOrius’ consumption ofA. gossypii was intermediate. Average daily predation was higher forD. tamaninii than forM. caliginosus, but was not different from bothOrius species. FemaleD. tamaninii exhibited a typical type-II functional response when preying on varying densities ofA. gossypii nymphs.     

Evaluation of lycosid,micryphantid and linyphiid spiders as predators ofRhopalosiphum padi (Hom.: Aphididae) and their functional response to prey density-laboratory experiments

Laboratory experiments were performed to determine the potential of dominant spider species in winter wheat in Germany,Erigone atra (Blackwall),Lepthyphantes tenuis (Blackwall) andPardosa agrestis (Westring) adults and youngs, in suppressing the population ofRhopalosiphum padi (L.) on wheat plants and their functional response to different aphid densities. The presence of spiders significantly caused between 34 and 58% reduction in aphid population development on wheat plants compared to the aphid population in the absence of spiders. The functional response curves for these spiders as predators ofR. padi seem to descrive a typical type II functional response with the prey consumed increasing to a plateau as aphid densities increased. Prey killed without eating was linear on prey density.     

Developmental times and oviposition rates of predatory mitesTyphlodromus pyri andAmblyseius andersoni (Acari: Phytoseiidae) reared on different foods

The developmental times and the reproduction of two resistant Italian strains ofTyphlodromus pyri Scheuten andAmblyseius andersoni (Chant) were studied in the laboratory by rearing them on the spider mitesPanonychus ulmi (Koch) andEotetranychus carpini (Oud.), on the eriophyidColomerus vitis (Pgst.) and on pollen ofMesembryanthemum criniflorum. The response ofT. pyri andA. andersoni females to a spider mite supply (P. ulmi orE. carpini) of 4, 8 and 16 adult female prey per female predator per day was also studied.Development ofT. pyri onE. carpini andC. vitis required a shorter period than onM. criniflorum pollen, while intermediate values were recorded forP. ulmi. When the highest number of prey was offered, the influence of different foods on oviposition rates ofT. pyri was not significant. An increase in spider mite supply favoured a shorter pre-oviposition period and higher oviposition rates.Development ofA. andersoni was faster on pollen than on spider mites, while intermediate values were found concerningC. vitis. Differences statistically significant were recorded for development onP. ulmi andC. vitis. Colomerus vitis proved to be the more suitable food in terms of oviposition. The oviposition rate decreased when feeding uponP. ulmi, but reached intermediate values onE. carpini andM. criniflorum. Increasing spider mite densities caused shorter pre-oviposition times and higher oviposition rates. Using a given number ofE. carpini females, rather than those ofP. ulmi, resulted in higher oviposition rates and shorter pre-oviposition times.For both predators, the results suggest a higher intrinsic rate of population increase onE. carpini orC. vitis than onP. ulmi.The research was supported by a grant from Regione Veneto (Lotta biologica ed integrata nel controllo di insetti ed acari dannosi).The general lines of the research have been planned by C. Duso. The authors contributed equally to the experimental work.     

Host specificity ofPareuchaetes insulata (Lep.: Arctiidae), a biological control agent forChromolaena odorata (Compositae)

Larvae of the arctiid moth,Pareuchaetes insulata, from Florida fed on the leaves ofChromolaena odorata, a serious composite, alien weed in Natal, South Africa. In starvation test trials using 48 plant species,P. insulata completed its development onC. odorata andAgeratum houstonianum. Subsequent attempts to cultureP. insulata on these two plants was only successful onC. odorata. The biology ofP. insulata is similar to that of two other well studiedPareuchaetes species namelyP. pseudoinsulata andP. aurata aurata. Repeated defoliation ofC. odorata byP. insulata could contribute to its control as has been found withP. pseudoinsulata in Guam.Pareuchaetes insulata has been approved for release as a biological control agent ofC. odorata in South Africa.     

Acceptance of eggs ofRivula atimeta,Naranga aenescens [Lep.: Noctuidae] andHydrellia philippina [Dipt.: Ephydridae] by insect predators on rice

Eight insect predators common in the rice ecosystem in the Philippines were compared in the laboratory on their ability as to feed on the eggs of green hairy caterpillar,Rivula atimeta Swinhoe. A ranking, based on feeding rates was made:Metioche vittaticollis (Stål) (Gryllidae) was the most voracious predator, followed byAnaxipha longipennis (Serville)(Gryllidae), Ophionea nigrofasciata (Schmidt-Goebel)(Carabidae), Micraspis nr.crocea (Mulsant) (Coccinellidae) andConocephalus longipennis (de Haan) (Tettigoniidae). Also the smallCyrtorhinus lividipennis Reuter (Miridae), readily fed upon the eggs.Paederus fuscipes Curtis (Staphilinidae) andCoccinella repanda (Thunberg) (Coccinellidae) fed to a very limited extent.Metioche vittaticollis andCyrtorhinus lividipennis were also tested on eggs of green semilooper,Naranga aenescens Moore, and rice whorl maggot,Hydrellia philippina Ferino. The feeding rate ofM. vittaticollis was similar on the 3 different preys, butC. lividipennis had a higher feeding rate onN. aenescens eggs. In 1.6 m² field cages, different densities ofM. vittaticollis andO. nigrofasciata were allowed to feed on exposedR. atimeta eggs during 2 days.Metioche vittaticollis consumed 13 and 26 eggs at predator densities of 1 and 2 per cage respectively, but was not much higher at density 8. Predation byO. nigrofasciata was not significant.     

Conservation of two predator species for biological control ofChrysophtharta bimaculata (Col.: Chrysomelidae) in tasmanian forests

Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae) is a major defoliator of regeneration eucalypt trees in Tasmania causing a significant reduction in height and diameter increment of trees which reduces wood volume per hectare. A study to conserve and enhance the efficiency of coccinellid species chieflyCleobora mellyi (Mulsant) (Coleoptera: Coccinellidae), and the cantharid,Chauliognathus pulchellus (Macleay) (Coleoptera: Cantharidae), for the biological control ofC. bimaculata was conducted in young regeneration forests in southern Tasmania from 1991–92. Cantharid adults and coccinellid adults and larvae feed onC. bimaculata eggs and, to a lesser extent, young larvae. The study found that coccinellids were more active throughout the egg and early (1^st and 2^nd) stage ofC. bimaculata. The cantharid, however was active only during the egg stage of the prey and then disappeared from the plantation. The coccinellids were therefore the most useful predators, but their population declined when the prey reached the 3^rd and 4^th stages. As shortage of food may account for this decline, supplementary food was provided in the form of sucrose sprays or sugar granules at a feeding station. This resulted in the retention of both predators and particularly the coccinellids and enhanced their efficacy.     

Temperature-dependent functional response of Euborellia annulipes (Dermaptera: Anisolabididae) preying on Plutella xylostella (Lepidoptera: Plutellidae) larvae

Temperature mediates trophic interactions, including relationships between insect pests and predators, and functional response studies are often used to determine the suitability of predators as biocontrol agents. We investigated the effects of temperature on the functional response of Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae) preying on Plutella xylostella (L.) (Lepidoptera: Plutellidae) larvae. Predation rate, type of functional response, attack rate (a'), handling time (T_h), and maximum predation rate (T/T_h) of the predator were estimated using seven prey densities and three thermal conditions. The functional response of E. annulipes to P. xylostella was temperature-dependent, type III under the lower temperatur (18°C and 25 °C) , and type II at 32 °C. We observed increasing values of a’ in 25 °C and 32 °C, decreasing values of Th and highest T/T_h as the thermal condition increased. Our findings suggest that E. annulipes could be effective to control P. xylostella under different thermal conditions, however its predation behavior changes according to temperature variation.     

Life-history and feeding habit ofTyphlodromus bambusae,a specific predator ofSchizotetranychus celarius (Acari: Phytoseiidae: Tetranychidae)

Studies on the life history and food habit ofTyphlodromus bambusae Ehara were carried out under aboratory conditions of 25±1°C, 60–80%rh and 159l:d.The egg-to-egg period of the predator which fed on eggs of the long-seta form ofSchizotetranychus celarius (Banks) was longer than those of the three phytoseiid species,Amblyseius eharai Amitai et Swirski,A. longispinosus (Evans) andA. paraki Ehara, which fed onTetranychus urticae Koch. The sex-ratio ofT. bambusae was not significantly different from those of the other three species. The long ovipositional period and the rather constant, low, reproductive rate observed inT. bambusae were remarkable.The intrinsic rate of natural increase (r _m) ofT. bambusae was 0.164 per day and it was very similar to ther _m of its prey,S. celarius. This observation supports the idea that there is a coincidence between the life-histories of spider-mite prey and their specific phytoseiid predators.Although females ofT. bambusae could feed on eggs ofAponychus corpuzae Rimando orSchizotetranychus recki Ehara which cohabit withS. celarius onSasa bamboo, their oviposition rate was lower than that onS. celarius eggs.Schizotetranychus celarius is thought to be a profitable prey species forT. bambusae, whileS. recki andA. corpuzae are only subsidiary, or alternative, prey.     

Development and survival ofOrius albidipennis andO. levigatus (Het.: Anthocoridae) on various diets

The effect of various diets on nymphal development and survival of two predaceous anthocorid bugs,Orius albidipennis (Reuter) andO. laevigatus (Fieber) was investigated in the laboratory. Five different diets were compared: eggs ofEphestia kuehniella Zeller; eggs ofE. kuehniella plus mixed flower pollen; only mixed flower pollen; pollen from sweet pepper (Capsicum annuum L. cv. Mazurka) flowers; and sweet pepper plants. A high percentage of predators successfully completed nymphal development on those diets containing lepidopterous eggs. When fed on sweet pepper pollen, the survival percentages were 65% forO. laevigatus and 38% forO. albidipennis. No nymphs of either species completed the nymphal stage on mixed flower pollen or on sweet pepper plants. Development was significantly faster on diets containing eggs ofE. kuehniella. Results are discussed in relation to the capability of the bugs to survive periods of prey scarcity and to the optimization of release strategies for these predators in the greenhouse.     

Dryinid (Hym.: Dryinidae) parasitoids ofDalbulus leafhopper (Hom.: Cicadellidae) in Mexico

Little is known about the natural enemies of the leafhopperDalbulus spp. (Homoptera: Cicadellidae). Searches for its dryinid (wasps) parasitoids were made in Jalisco, Mexico. Jalisco contains the greatest number ofDalbulus species, and is considered to be near to the center of origin of this leafhopper genus and its host plants: maize, teosintes (Zea spp.) and gamagrasses (Tripsacum spp.). The dryinidGonatopus bartletti was found parasitizingD. maidis on maize and on annual teosinteZea mays spp.parviglumis. G. flavipes was found parasitizingD. elimatus on perennial teosinteZ. perennis; and a new speciesG. moyaraygozai andAnteon ciudadi parasitizingD. quinquenotatus onTripsacum pilosum andT. dactyloides. Parasitism by dryinids was found at altitudes of 680–2,000 m.Dalbulus maidis, the leafhopper species which causes the greatest losses in maize in Latin America, was found to be parasitized from 680–1,760 m. TheDalbulus species associated with annual host plants (maize andZ. mays spp.parviglumis) were parasitized by dryinids during the rainy season, while theDalbulus species associated with perennial host plants (Z. perennis andTripsacum) were parasitized by dryinids during both the rainy and dry season. The greatest diversity of dryinid parasitoids ofDalbulus spp. and the highest levels of parasitism were recorded from perennial plants, indicating that such species are reservoirs of natural enemies ofDalbulus spp.     

Actinophages and restriction enzymes fromMicromonospora species (Actinomycetales)

Summary To develop a screening procedure for the detection of restriction endonucleases in micromonosporae and catellatosporae based on efficiency of plating, eight different actinophages were isolated from soils enriched withMicromonospora species and one fromCatellatospora-enriched soil. The lytic actinophages all contained double-stranded DNA and the majority appeared, when examined by electron microscopy, to belong to Ackermann's type B1 since they had isometric heads and noncontractile tails. One actinophage was classified as type C1 because of its isometric head and very short noncontractile tail. The host ranges of the actinophages were determined on strains ofMicromonospora and selected species from other actinomycete genera of cell wall chemotype II. Type II restriction enzymes were isolated fromM. echinospora ssp.echinospora (ATCC 15837),M. purpurea (ATCC 15835) andM. zionensis (LL-100-125) and were designatedMecI,MpuI andMziI, respectively. Restriction enzymesMecI andMpuI are isoschizomers ofXhoI, whileMziI is an isoschizomer ofPvuII.     

The non-abundant nutrient (NAN) concept as a determinant of predator-prey fitness

We applied the non-abundant nutrient concept (NAN), an off-shoot from the ecological concept known as Liebig’s “law of the minimum” or the concept of “limiting factors”, to explain why certain predators are well fitted while others are poorly fitted to their prey. The generalist predatorsGeocoris punctipes (Say) (Heteroptera: Lygaeidae) andChrysoperla carnea Stephens (Neuroptera: Chrysopidae) and the specialist predator of whitefliesSerangium parcesetosum Sicard (Coleoptera: Coccinellidae) were compared, nutritionally, to determine their relative propensities for predation onEphestia kuehniella (Zeller) (Lepidoptera: Phycitidae) eggs, silverleaf whitefly nymphsBemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) andAphis gossypii Glover (Homoptera: Aphididae). Using two prey content parameters, biomass (measured as dry weight) and methionine (the least abundant protein amino acid in all three prey species), we made estimates of how many of the various kinds of prey would need to be consumed to satisfy each predator’s growth requirements to reach the adult stage. From this information and observations regarding developmental periods, prey handling times, extraction efficiencies and conversion efficiencies, we developed a daily time budget for each predator feeding on each of the three types of prey. The number of prey and the time required to satisfy the methionine requirement were generally much greater than the numbers and time required for meeting biomass requirements. Of the three species of predators, onlyS. parcesetosum could survive and reproduce within a reasonable time budget with whiteflies as prey. Cotton aphids also appeared to be a marginal prey with respect to methionine content.     

Host specificity and aspects of the biology ofCalligrapha pantherina (Col.: Chrysomelidae), a biological control agent ofSida acuta [Malvaceae] andS. rhombifolia in Australia

The host specificity of a chrysomelid beetle,Calligrapha pantherina Stål, from Mexico, was verified in the CSIRO quarantine facilities in Brisbane, Australia on 80 species of plants in 28 families, either closely related to Malvaceae or in families containing economically important species.C. pantherina oviposited and developed successfully on its preferred host,S. acuta, and less successfully onS. rhombifolia andS. spinosa, all of which are weeds in Australia. Aspects of oviposition, larval development, and adult feeding and longevity ofC. pantherina are described.C. pantherina was released in Australia during 1989 and readily established onS. acuta but established at only a few sites onS. rhombifolia.     

Insecticidal effectiveness ofMammea Americana (Guttiferae) extracts on larvae ofDlabrotica Virgifera Virgifera (Coleoptera:Chrysomelidae) andTrichoplusia Ni (Lepidoptera:Noctuidae)

Seed and leaf extracts ofMammea americana (mamey apple) have a historical use as a biopesticide with the active components previously characterized. We reexamined the utility of this natural bioinsecticide in light of existing sources of material as a by-product of the fruit processing industry. Our results addDiabrotica virgifera virgifera andTrichoplusia ni to the list of insects which are susceptible to the insecticidal ingredients ofM. americana and confirms earlier reports of activity againstBlatella germanica, Periplaneta americana, andPlutella xylostella. We report LD5Os for crude hexane extracts ofM. americana leaves and seeds againstT. ni. These materials represent renewable sources of bioinsecticides for agriculture, and should regenerate interest in coumarin-type compounds for novel pesticidal action.     

Reevaluation of Mimosa biuncifera and M. texana (Leguminosae: Mimosoideae)

Mimosa biuncifera, as currently defined in southwestern United States, is shown to comprise two related species,M. biuncifera s. str. andM. texana, distinguished primarily by position of the nodal aculei. Taxonomic synonyms ofM. biuncifera areM. lindheimeri andM. warnockii (the first undisputed, the second provisional);M. texana includesM. wherryana.     

Host-associated fitness variation in a seed beetle (Coleoptera: Bruchidae): evidence for local adaptation to a poor quality host

The geographic distributions of many generalist herbivores differ from those of their host plants, such that they experience coarse-grained spatial variation in natural selection on characters influencing adaptation to host plants. Thus, populations differing in host use are expected to differ in their ability to survive and grow on these host plants. We examine host-associated variation in larval performance (survivorship, development time, and adult body weight) and oviposition preference, within and between two populations ofStator limbatus (Coleoptera: Bruchidae) that differ in the hosts available to them in nature. In one population,Acacia greggii (Fabaceae: Mimosoideae) andCercidium microphyllum (Fabaceae: Caesalpininoideae) are each abundant, while in the second population onlyC. floridum andC. microphyllum are present. In both populations, egg-to-adult survivorship was less than 50% onC. floridum, while survivorship was greater than 90% onA. greggii. Most of the mortality onC. floridum occurred as larvae were burrowing through the seed coat; very low mortality occurred during penetration of the seed coat ofA. greggii. Significant variation was present between populations, and among families (within populations), in survivorship and egg-to-adult development time onC. floridum; beetles restricted toCercidium in nature, without access toC. floridum, survived better and developed faster onC. floridum than beetles that had access toA. greggii. Large host effects on body size were detected for female offspring: females reared onA. greggii were larger than those reared onC. floridum, whereas male offspring wee approximately the same size regardless of rearing host. Trade-offs between performance onC. floridum andC. floridum were not detected in this experiment. Instead, our data indicate that development time and survivorship onC. floridum may be largely independent of development time and survivorship onA. greggii. Patterns of oviposition preference corresponded to the observed patterns of host suitability: in laboratory preference tests, beetles with access toA. greggii in nature tended to prefer this host more than beetles without access to this host in nature.     

Host specificity ofAcanthoscelides quadridentatus andA. Puniceus [Col.: Bruchidae] for biological control ofMimosa pigra (with preliminary data on their biology)

The biology and host specificity of the seed-feeding bruchids,Acanthoscelides quadridentatus (Schaeffer) andA. puniceus Johnson, from Mexico were studied in quarantine facilities in Australia. Distinguishing characters in the genitalia of each species are illustrated. Oviposition was recorded on 16 of 73 species of plants tested but larvae died without entering pods or seeds, except onMimosa invisa K. F. P. von Martius andM. pigra L. Larvae entering seeds ofM. invisa died in the first instar. The bruchids were clearly specific toM. pigra and were subsequently released as part of a program for biological control of this weed in the Northern Territory, Australia in April 1983 and thailand in July 1984.      

Influence of temperature onOpius dissitus (Hym.: Braconidae), a parasitoid ofLiriomyza trifolii (Dipt.: Agromyzidae)

Rearing experiments at different temperatures (10, 15, 20, 25 and 30°C) were made onOpius dissitus Muesebeck, a parasitoid ofLiriomyza trifolii (Burgess). Temperatures between 20 and 30°C were optimal for the development ofO. dissitus, which was able to adapt to relatively high temperatures despite its holarctic origin.