Effect of methanolic extracts of neem (Azadirachta indica A. Juss) and bakain (Melia azedarach L) seeds on oviposition and egg hatching of Earias vittella (Fab.) (Lep., Noctuidae)

Abstract: The effects of methanolic extracts of neem ( Azadirachta indica ) and bakain ( Melia azedarach ) seeds on the oviposition behaviour and hatchability of eggs of Earias vittella were investigated under laboratory conditions. Treatments included 2, 4, 6, 8 and 10% concentrations of both extracts to compare with nimbecidine and untreated control. When able to choose, the adults preferred to lay a greater number of eggs on the untreated portion of the oviposition substrate (muslin) compared with the extract-treated portion. However, under no-choice conditions, higher concentrations of extracts caused proportionate reductions in the number of eggs laid. The extracts also manifested repellent activity by reducing the number of eggs laid even when the ovipositing females were not in direct contact with the extracts. Eggs laid on extract-treated oviposition substrate exhibited reduced hatching and marked adverse effects on hatching were noticed when the eggs were dipped in different concentrations of extracts. Adults fed on an extract-containing sucrose diet laid significantly fewer eggs with poor hatching. There was no egg laying when the moths were fed on a sucrose diet containing 6, 8 and 10% neem and 10% bakain extracts.     

Influence of mating on sexual receptivity and oviposition in the mosquito, Culex tarsalis

ABSTRACT. Mated females of Culex tarsalis Coq. (Diptera, Culicidae) were receptive to additional insemination after gonotrophic activity. Sexual receptivity was not renewed in mated, aged nulliparous females. Insemination was determined by the detection in females of sperm labelled with adenine-³H(G) after matings with radio-labelled males. When females were deprived of males after their first insemination, the production of fertile eggs was reduced and oviposition activity was altered throughout successive gonotrophic cycles.     

Trophic egg laying in the spider, Amaurobius ferox: mother-offspring interactions and functional value

Offspring of the spider Amaurobius ferox (Araneae, Amaurobiidae) were provided with trophic eggs of their mother the day after their emergence from the egg sac. This precisely timed egg laying followed after a series of mother-offspring interactions involving specific behaviors. Experiments showed that the trophic egg laying of the mother (providing she is in the appropriate reproductive condition) necessitated not only their presence, but also the stimulating behavior of the spiderlings. By stimulating their mother the spiderlings actually inhibited the normal maturation of the second generation of maternal eggs and prompted the release. Comparing to the trophic egg-deprived clutches, the clutches provided with the trophic eggs developed with higher body mass, earlier moulting and matriphagy. More offspring survived at the matriphagy with the mother normally provisioning the first clutch with trophic eggs rather than with the mother that did not produced the trophic eggs for her first clutch but for her second clutch. By turning her potential second generation into food, the mother increases her reproductive success.     

On a Reproductive Stage-Structured Model for the Population Dynamics of the Malaria Vector

A reproductive stage-structured deterministic differential equation model for the population dynamics of the human malaria vector is derived and analysed. The model captures the gonotrophic and behavioural life characteristics of the female Anopheles sp. mosquito and takes into consideration the fact that for the purposes of reproduction, the female Anopheles sp. mosquito must visit and bite humans (or animals) to harvest necessary proteins from blood that it needs for the development of its eggs. Focusing on mosquitoes that feed exclusively on humans, our results indicate the existence of a threshold parameter, the vectorial reproduction number, whose size increases with increasing number of gonotrophic cycles, and is also affected by the female mosquito’s birth rate, its attraction and visitation rate to human residences, and its contact rate with humans. A stability analysis of the model indicates that the mosquito can establish itself in the environment if and only if the value of the vectorial reproduction number exceeds unity and that mosquito eradication is possible if the vectorial reproduction number is less than unity, since, then, the trivial steady state which always exist is unique and is globally and asymptotically stable. When a persistent vector population steady state exists, it is locally and asymptotically stable for a range of reproduction numbers, but can also be driven to instability via a Hopf bifurcation as the reproduction number increases further away from unity. The model derivation identifies and characterizes control parameters relating to activities such as human-mosquito contact and the mosquito’s survival chances between blood meals and egg laying. Our results show that the total mosquito population size increases with increasing number of gonotrophic cycles. Therefore understanding the fundamental aspects of the mosquito’s behaviour provides a pathway for the study of human-mosquito contact and mosquito population control. Control of the mosquito population densities would ultimately lead to malaria control.     

Variations in prey consumption of centipede predators in forest soils as indicated by molecular gut content analysis

Predation is an important ecological factor driving animal population structures, community assemblages and consequently ecosystem stability and biodiversity. Many environmental factors influence direction and intensity of predation, suggesting that trophic linkages between animals vary between different habitats. This in consequence has particular relevance in anthropogenically altered habitats such as managed forests, where disturbance regime, tree composition and stand age may change the natural food web structure. We investigated how prey consumption of three common centipede predators (Lithobius spp., Chilopoda), representing two body sizes varies between four differently managed forest types in two regions across Germany. We hypothesized that prey preference of these generalist predators is independent of forest type but rather driven by habitat structure, prey abundance and predator body size. Applying specific PCR assays to test for DNA of three abundant prey groups, i.e. Collembola, Diptera and Lumbricidae, in the predators’ guts, we tracked trophic interactions. The results showed that management type indeed has no influence on centipede prey consumption but depth of litter layer and soil pH. Trophic interactions varied between the two sampled forests regions mainly due to changes in the detection of Lumbricidae and Diptera. Also, effect of litter layer and prey abundance significantly differed between the smaller L. crassipes and the larger L. mutabilis, indicating a body size effect. The results complement food web analyses using fatty acids and stable isotopes by elucidating trophic interactions in soil in unprecedented detail.     

Policing behaviour towards virgin egg layers in a polygynous ponerine ant

The majority of colonies of Gnamptogenys menadensis in Sulawesi lack queens and several workers ('gamergates') mate and reproduce instead. Virgin workers lay morphologically specialized trophic eggs which are fed to larvae. Some of these virgins switch to male eggs when gamergates are experimentally removed. Three distinct patterns of oogenesis thus result in: (1) trophic eggs; (2) reproductive eggs (unfertilized) laid by virgin workers; and (3) reproductive eggs laid by gamergates, whose ovarioles are always longer than those of virgin workers. We investigated the behavioural regulation of ovarian activity in virgin workers by temporarily excluding gamergates. In 12 groups of 35-45 virgins, a few workers became dominant and started to lay reproductive eggs. Once gamergates were reintroduced, sterile workers attacked and immobilized workers with enlarged ovaries (confirmed by dissection of 173 individuals), which often died as a result. Gamergates were never aggressive towards new egg layers. Aggression was not triggered by divergence in colony odours, as it was absent in control experiments in which six colonies were divided in half, with each part containing gamergates, and reunited after 50 days. Our results show that sterile workers discriminate against new egg layers, given that their ovaries are not as developed as those of gamergates. Olfactory detection of different levels of ovarian activity thus appears possible. Mesh experiments indicated that the putative pheromones are nonvolatile and require physical contact for transmission. Aggressive behaviour directed at reproducing workers can be interpreted as worker policing. In G. menadensis, worker policing results in virgins laying only trophic eggs. Copyright 1999 The Association for the Study of Animal Behaviour.     

Spatial feeding preferences of ornithophilic mosquitoes,blackflies and biting midges

The section of habitat used by particular bloodsucking insects when seeking bloodmeals may influence the spectrum of hosts to which they have access and consequently the diseases they transmit. The vertical distribution of ornithophilic bloodsucking Diptera (Culicidae, Simuliidae and Ceratopogonidae) was studied using bird‐baited traps set at both ground and tree canopy levels. In total, 1240 mosquito females of eight species, 1201 biting midge females of 11 species, and 218 blackfly females of two species were captured during 2003–2005. Culex pipiens (L.) (Diptera: Culicidae) was found to prefer ground‐level habitats, whereas Anopheles plumbeus (Stephens) (Diptera: Culicidae), biting midges [Culicoides spp. (Diptera: Ceratopogonidae)] and Eusimulium angustipes (Edwards) (Diptera: Simuliidae) preferred the canopy. The results of this study with regard to Cx. pipiens behaviour differ from those of most previous studies and may indicate different spatial feeding preferences in geographically separate populations. The occurrence of E. angustipes in the canopy is concordant with its role in the transmission of avian trypanosomes. These findings may be important for surveillance programmes focusing on ornithophilic Diptera which transmit various pathogenic agents.     

Ear tags--a prospective method for the long-term protection of livestock from ectoparasites

Ear tags are a most effective method for protecting animals from ectoparasites for a long time with minimum expenditures and without polluting the environment. The method is based on a long evaporation of highly toxic insecticides, mainly pyrethroids, homogeneously spread in the substance of the filler which by penetrating into the animal's hair provide its constant protection. Ear tags were successfully used for control of population of bloodsucking Diptera, mites and myiasis flies.     

Experience‐ and age‐mediated oviposition behaviour in the yellow fever mosquito Stegomyia aegypti (=Aedes aegypti)

In repeated behaviours such as those of feeding and reproduction, past experiences can inform future behaviour. By altering their behaviour in response to environmental stimuli, insects in highly variable landscapes can tailor their behaviour to their particular environment. In particular, female mosquitoes may benefit from plasticity in their choice of egg‐laying site as these sites are often temporally variable and clustered. The opportunity to adapt egg‐laying behaviour to past experience also exists for mosquito populations as females typically lay eggs multiple times throughout their lives. Whether experience and age affect egg‐laying (or oviposition) behaviour in the mosquito Stegomyia aegypti (=Aedes aegypti) (Diptera: Culicidae) was assessed using a wind tunnel. Initially, gravid mosquitoes were provided with a cup containing either repellent or well water. After ovipositing in these cups, the mosquitoes were blood‐fed and introduced into a wind tunnel. In this wind tunnel, an oviposition cup containing repellent was placed in the immediate vicinity of the gravid mosquitoes. A cup containing well water was placed at the opposite end of the tunnel so that if the females flew across the chamber, they encountered the well water cup, in which they readily laid eggs. Mosquitoes previously exposed to repellent cups became significantly more likely to later lay eggs in repellent cups, suggesting that previous experience with suboptimal oviposition sites informs mosquitoes of the characteristics of nearby oviposition sites. These results provide further evidence that mosquitoes modify behaviour in response to environmental information and are demonstrated in a vector species in which behavioural plasticity may be ecologically and epidemiologically meaningful.     

An order-specific monoclonal antibody to Diptera reveals the impact of alternative prey on spider feeding behavior in a complex food web

Generalist predators have the capacity to restrict pest population growth, especially early in the season before densities increase. However, their polyphagous feeding habits sometimes translate into reduced pest consumption when they target alternative prey. An order-specific monoclonal antibody was developed to examine the strength of trophic connections between Diptera, a major category of non-pest prey, and linyphiid spiders in alfalfa. We report the development and characterization of a monoclonal antibody with order-level specificity to Diptera. This antibody elicited strong absorbance to 22 Diptera from 13 families, no false-positive reactivity to non-dipteran invertebrates, and antigen detection periods following prey consumption that were comparable between spiders. Over 900 field-collected females of the linyphiid spiders Erigone autumnalis and Bathyphantes pallidus were screened for Diptera antigen. Significantly more B. pallidus screened positive for Diptera (40%) compared to E. autumnalis (16%), indicating differential reliance on these prey. In parallel with the collection of spiders for gut-content analysis, prey availability was estimated at web sites. The two spiders exhibited different feeding responses to prey availability. Consumption of Diptera by B. pallidus was strongly correlated with Diptera abundance whilst the availability of other potential prey did not influence predation rates. Conversely, E. autumnalis did not prey upon Diptera in proportion to availability, but increased Collembola activity-density reduced dipteran consumption. Integration of molecular gut-content analysis with precise sampling of prey demonstrated how two closely related linyphiid spiders exhibit different feeding responses to the availability of prey under natural field conditions. Elucidating the feeding preferences of natural enemies is critical to effective incorporation of biological control by generalist predators in the management of agricultural pests.     

Prey Capture Behaviour in the Social Spider Anelosimus eximius (Araneae: Theridiidae): Responses to Prey Size and Type

Some species of web building spiders use different capture tactics for different prey types. The main factors influencing the attack behaviour are the ability of the insect to escape, the risks of injury to the spiders and prey size. This study evaluated the effects of size and prey type on prey capture behaviour of the social spider Anelosimus eximius as influenced by the number of spiders attracted by prey movements that did not bite until the immobilization (bystanders) and the number of spiders that contributed to prey immobilization (catchers). We carried out a two‐factor (prey size and type) experiment offering prey belonging to four orders: Diptera, Lepidoptera, Hymenoptera and Orthoptera, in a size gradient within each prey type. Both factors influenced the number of spiders recruited as bystanders, but only prey body size influenced the number of catchers in the subduing process. The possible advantages of the presence of bystanders around the interception site are discussed.     

Studies on the basic components of the predation ofPhytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae)

The basic components of the predation of Phytoseiulus persimilisAthias-Henriot feeding upon eggs of Tetranychus urticaeKoch were studied in an open system where the predator could disperse freely. The type of the functional response of the predator to the density of its prey was the same as that studied so far in a closed system, i.e.,Holling's Type 2. The search rate of the predator, however, was much lower in comparison with the result from a closed system. The oviposition of the predator per day was only weakly related to prey densities higher than 10 per leaf disc. But the emigration rate was inversely dependent upon the initial prey density up to 60 per leaf disc. The searching behaviour of the predator was influenced by both the web density spun by T. urticae and the density of the prey: the predator searched for its prey intensively only after it had contact with web. Mutual interference was observed in prey consumption, but not in the emigration rate. The emigration rate was largely dependent upon the prey density available per predator.     

Is the Starling Sturnus vulgaris a determinate layer?

European Starlings Sturnus vulgaris have been said to be determinate layers, that is, they do not react to egg removals by laying extra eggs nor to egg additions by laying fewer eggs. Especially in species with a relatively small clutch-size, such as the Starling, it is important to start these experiments early during the laying period to give the laying female the possibility of reacting to these additions and/or removals. I report here addition ( n = 11 nests) and removal experiments ( n = 35) early in laying period in a captive Starling colony. Additional information is presented about the development of incubation behaviour, a good predictor of clutch-size. When three eggs were added to nests at 1500h on the first day of laying, females laid the normal number of eggs, and incubation behaviour developed regularly. Egg removals (one egg on three successive days) that started early in the laying period (at 1500h on the first day or at 0800h on the second day) arrested the development of incubation behaviour and resulted in the laying of extra eggs. Removals later in the laying period had no effect on the number of eggs laid nor on incubation behaviour. Following Kennedy's (1991) terminology, the starling is an addition-determinate, and appears to be a removal-indeterminate, layer.     

Ovipositional Behavior in Predator and Prey Blowflies

In this study we analyzed the ovipositional behavior of C. albiceps, C. megacephala and L. eximia in response to previous presence of larvae of different species, both predator and prey. The preference for substrates that previously had had no larvae was predominant for all species. However, the experiments showed that C. megacephala and L. eximia avoid laying eggs principally in patches with previous presence of C. albiceps larvae. The implications of these results for the necrophagous Diptera community dynamics are discussed.     

Diel timing and frequency of sugar feeding in the mosquito Anopheles gambiae, depending on sex, gonotrophic state and resource availability

Little is known about the sugar-feeding behaviour of equatorial Africa's principal vector of malaria, Anopheles gambiae Giles (Diptera: Culicidae). It is suspected to feed on plant sugar infrequently, but possibly the timing depends on environmental circumstances, and males may differ markedly from females. These points of uncertainty were clarified in the laboratory, by monitoring both diel and longterm sugar-feeding activity in both sexes. Males fed on sugar in a nocturnal diel rhythm closely approximating non-specific flight activity. Female diel sugar-feeding patterns resembled published rhythms and cycles of host seeking. Males sugar fed nightly at an average frequency of about twice per night, sustained over 17 days. This was substantially higher than the sugar-feeding frequency of females that were allowed both blood and oviposition sites every night: they averaged about one sugar feed in every 4 nights. These females fed on sugar between gonotrophic cycles, after eggs were mature but before the next bloodmeal. They did not sugar feed during the 2 days after blood feeding, while blood was being digested and the eggs developed. A slight delay in the availability of either the oviposition site or blood led to an increase in female sugar-feeding frequency: they averaged more than once per night until the delayed resource was made available. These observations support the conclusion that sugar feeding is a normal part of the biology of both sexes of An. gambiae.     

Egg cannibalism by Coleomegilla maculata lengi neonates: preference even in the presence of essential prey

Abstract 1. Egg cannibalism among coccinellids has been reported widely, however reasons why this type of behaviour is observed so frequently have been neglected. This experiment was undertaken to clarify whether cannibalistic behaviour is advantageous to Coleomegilla maculata lengi Thimberlake neonates and to understand the reasons for high levels of egg cannibalism.
2. Benefits gained by neonate cannibals were ascertained by comparing survival, developmental time, and second-instar weight of C. maculata larvae that were allowed to cannibalise conspecific eggs or not. Preference and behaviour tests were also conducted to assess the reasons for high levels of egg cannibalism.
3. Cannibal neonates grew faster and were heavier than non-cannibals. The developmental time of neonates was influenced more by prey vulnerability than by prey quality.
4. In choice tests, where three different proportions of conspecific eggs and aphids were offered (33–67, 50–50, and 67–33%), C. maculata neonates always consumed significantly more eggs. Manly's preference indexes indicated that neonates showed a consistent preference for conspecific eggs.
5. Seventy-five per cent of neonates observed went directly towards eggs and 90% of the first prey consumed by neonates were an egg. When aphids were painted with extract of crushed eggs and eggs with crushed aphids to determine whether neonates found eggs by chemical cues, neonates preferred aphids painted with egg extract to eggs painted with aphid extract.
6. It was concluded that C. maculata neonates benefited from cannibalistic behaviour. Moreover, egg cannibalism is not related only to frequency of encounter; chemical cues are also involved in egg searching.     

Neighbouring monocultures enhance the effect of intercropping on the turnip root fly (Delia floralis)

Knowledge of insect behaviour is essential for accurately interpreting studies of diversification and to develop diversified agroecosystems that have a reliable pest‐suppressive effect. In this study, we investigated the egg‐laying behaviour of the turnip root fly, Delia floralis (Fall.) (Diptera: Anthomyiidae), in an intercrop‐monoculture system. We examined both the main effect of intercropping and the effect on oviposition in the border zone between a cabbage monoculture [Brassica oleracea L. var. capitata (Brassicaceae)] and a cabbage‐red clover intercropping system [Trifolium pratense L. (Fabaceae)]. To investigate the border‐effect, oviposition was measured along a transect from the border between the treatments to the centre of experimental plots. Intercropping reduced the total egg‐laying of D. floralis with 42% in 2003 and 55% in 2004. In 2004, it was also found that the spatial distribution of eggs within the experimental plots was affected by distance from the adjoining treatment. The difference in egg‐laying between monoculture and intercropping was most pronounced close to the border, where egg‐laying was 68% lower on intercropped plants. This difference in egg numbers decreased gradually up to a distance of 3.5 m from the border, where intercropped plants had 43% fewer eggs than the corresponding monocultured plants. The reason behind this oviposition pattern is most likely that flies in intercropped plots have a higher probability of entering the monoculture if they are close to the border than if they are in the centre of a plot. When entering the monoculture, flies can pursue their egg‐laying behaviour without being disrupted by the clover. As the final decision to land is visually stimulated, flies could also be attracted to fly from the intercropped plots into the monoculture, where host plants are more visually apparent. Visual cues could also hinder flies in a monoculture from entering an intercropped plot. Other possible patterns of insect attack due to differences in insect behaviour are discussed, as well as the practical application of the results of this study.     

Caught in the web: Spider web architecture affects prey specialization and spider–prey stoichiometric relationships

Quantitative approaches to predator–prey interactions are central to understanding the structure of food webs and their dynamics. Different predatory strategies may influence the occurrence and strength of trophic interactions likely affecting the rates and magnitudes of energy and nutrient transfer between trophic levels and stoichiometry of predator–prey interactions. Here, we used spider–prey interactions as a model system to investigate whether different spider web architectures—orb, tangle, and sheet‐tangle—affect the composition and diet breadth of spiders and whether these, in turn, influence stoichiometric relationships between spiders and their prey. Our results showed that web architecture partially affects the richness and composition of the prey captured by spiders. Tangle‐web spiders were specialists, capturing a restricted subset of the prey community (primarily Diptera), whereas orb and sheet‐tangle web spiders were generalists, capturing a broader range of prey types. We also observed elemental imbalances between spiders and their prey. In general, spiders had higher requirements for both nitrogen (N) and phosphorus (P) than those provided by their prey even after accounting for prey biomass. Larger P imbalances for tangle‐web spiders than for orb and sheet‐tangle web spiders suggest that trophic specialization may impose strong elemental constraints for these predators unless they display behavioral or physiological mechanisms to cope with nutrient limitation. Our findings suggest that integrating quantitative analysis of species interactions with elemental stoichiometry can help to better understand the occurrence of stoichiometric imbalances in predator–prey interactions.     

Factors influencing diet variation in a generalist predator across its range distribution

Factors linked with intraspecific variation in trophic diversity are still poorly understood in generalist species like the Montagu’s harrier (Circus pygargus) but may have important implications for conservation management at a wide scale. We described geographic patterns of Montagu’s harrier diet across Eurasia, gathering diet data from 30 studies in 41 areas from 11 countries. We grouped prey as invertebrates, reptiles, small mammals, large mammals, eggs, small birds and large birds, and calculated the contribution of each prey type to the diet (as % biomass) and Shannon’s Diversity Index for each study site. We analysed qualitative estimates of prey abundance in relation to latitude and longitude, then diet composition in relation to habitat of the study area and prey abundance estimates. Diet diversity of Montagu’s harriers increased from north to south, while abundance of all prey groups other than small mammals showed the opposite trends. Agricultural areas in northern latitudes seemed to hold high densities of small mammals, but low densities of alternative prey. Overall, birds were the main prey in most of Montagu’s harrier’s distribution range, although the relative importance of each prey type in the diet was significantly explained by its local abundance and habitat, confirming the opportunistic foraging strategy of this raptor species. Consumption of mammals was an exception to this trend, being negatively associated with the abundance of alternative prey, suggesting that this prey is not preferred. Trophic diversity in this species could be influenced by land-use changes through variations in the abundance and availability of prey, which could impact its population dynamics. This may be particularly important for northern populations of Montagu’s harriers breeding in agricultural habitats, where trophic diversity is already low.     

The importance of body reserves for successful reproduction in the Tawny owl (Strix aluco)

One-quarter of Tawny owl nests fail to hatch young, mainly because the eggs are chilled and/or deserted. In 1973–74 automatic photography was employed at four nests near Oxford to relate the incubation behaviour of females to the ration of prey supplied to them by their mates. The eggs did not hatch in two nests and young fledged from only one of the others. Females were less attentive at the nests which failed during incubation and on average received less prey, but even at successful nests there were some nights when the female was supplied with less than her estimated daily food requirement. Female Tawny owls accumulate large reserves of fat and protein before laying. These buffer against any temporary inability of the male to provide sufficient food during incubation, and enable the female to stay on the nest rather than hunt for herself and risk the eggs becoming chilled. When prey are scarce, many females do not lay at all, and the ultimate factor determining whether breeding takes place may be the female's ability to acquire body reserves sufficient to provide a chance of breeding successfully.