Differences In Oviposition Rate Research Articles

In vitro acaricidal activity of Piper tuberculatum against Rhipicephalus (Boophilus) microplus

ABSTRACT Rhipicephalus (Boophilus) microplus has a strong impact on bovine health. The aim of this study was to evaluate the in vitro acaricidal activity of Piper tuberculatum extracts on R. (Boophilus) microplus ticks obtained from cattle. The adult immersion test (AIT) was used to estimate the inhibition of oviposition. Moreover, the larval package test (LPT) was performed. P. tuberculatum extracts at 100 mg/ml showed a mortality of 78% after 24 h in adult ticks, reaching 100% at 9 days. Moreover, the mortality rate was significantly different (p˂0.001) among the tested groups at 11 days. Probit regression analysis showed that the mean lethal concentration (LC50) of P. tuberculatum extracts was 20.30 mg/ml after 24 h. On day 11, there were significant differences in oviposition rate among the groups, with 56% oviposition in the control group, whereas no oviposition was observed (p˂0.01) in the groups treated with P. tuberculatum at 100 mg/ml. In the LPT, high mortality (56.00%) was found in the group treated with P. tuberculatum (50 mg/ml), whereas the control group had 2.67% (p˂0.01). The use of P. tuberculatum extracts (100 mg/ml) was highly effective as an acaricide, reaching a high mortality rate in adult R. microplus ticks.

Plasticity in Oviposition Site Selection Behavior in Drosophila suzukii (Diptera: Drosophilidae) in Relation to Adult Density and Host Distribution and Quality.

Flexibility in oviposition site selection under temporally shifting environmental conditions is an important trait that allows many polyphagous insects to flourish. Population density has been shown to affect egg-laying and offspring fitness throughout the animal kingdom. The effects of population density in insects have been suggested to be mutualistic at low densities, whereas intraspecific competition is exhibited at high densities. Here, we explore the effects of adult crowding and spatial resource variation on oviposition rate in the invasive pest Drosophila suzukii (Matsumura). In a series of laboratory experiments, we varied the density of adult males and females while holding oviposition substrate availability constant and measured per female oviposition rate using high and low-quality substrates. We found that oviposition behavior was affected more by substrate than adult density, though both variables had significant effects. When we varied the spatial arrangement of whole raspberries, we observed differences in oviposition rate and egg distribution between the grouped and solitary female treatments. Our results suggest that social interactions encourage oviposition, especially when exposed to unfamiliar or unnatural substrates. These results highlight the compensating effect of increased oviposition rate per female as adult populations decline. They will help researchers and crop managers better understand in-field population dynamics throughout the season as population densities change.

Effects of larval exposure to sublethal doses of Bacillus thuringiensis var. israelensis on body size, oviposition and survival of adult Anopheles coluzzii mosquitoes

BackgroundApplication of the larvicide Bacillus thuringiensis var. israelensis (Bti) is a viable complementary strategy for malaria control. Efficacy of Bti is dose-dependent. There is a knowledge gap on the effects of larval exposure to sublethal Bti doses on emerging adult mosquitoes. The present study examined the effect of larval exposure to sublethal doses of Bti on the survival, body size and oviposition rate in adult Anopheles coluzzii.MethodsThird-instar An. coluzzii larvae were exposed to control and sublethal Bti concentrations at LC20, LC50 and LC70 for 48 h. Surviving larvae were reared to adults under standard colony conditions. Thirty randomly selected females from each treatment were placed in separate cages and allowed to blood feed. Twenty-five gravid females from the blood-feeding cages were randomly selected and transferred into new cages where they were provided with oviposition cups. Numbers of eggs laid in each cage and mortality of all adult mosquitoes were recorded daily. Wing lengths were measured of 570 mosquitoes as a proxy for body size.ResultsExposure to LC70Bti doses for 48 h as third-instar larvae reduced longevity of adult An. coluzzii mosquitoes. Time to death was 2.58 times shorter in females exposed to LC70Bti when compared to the control females. Estimated mortality hazard rates were also higher in females exposed to the LC50 and LC20 treatments, but these differences were not statistically significant. The females exposed to LC70 concentrations had 12% longer wings than the control group (P < 0.01). No differences in oviposition rate of the gravid females were observed between the treatments.ConclusionsExposure of An. coluzzii larvae to sublethal Bti doses reduces longevity of resultant adults and is associated with larger adult size and unclear effect on oviposition. These findings suggest that anopheline larval exposure to sublethal Bti doses, though not recommended, could reduce vectorial capacity for malaria vector populations by increasing mortality of resultant adults.

Modeling mountain pine beetle (Dendroctonus ponderosae) oviposition

AbstractMountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae), is a significant forest disturbance agent with a widespread distribution in western North America. Population success is influenced by temperatures that drive phenology and ultimately the adult emergence synchrony required to mass attack and kill host trees during outbreaks. In addition to lifestage‐specific developmental rates and thresholds, oviposition timing can be a source of variance in adult emergence synchrony, and is a critical aspect of mountain pine beetle phenology. Adaptation to local climates has resulted in longer generation times in southern compared to northern populations in common gardens, and the role of oviposition rate in these differences is unclear. Oviposition rates and fecundity in a northern population have been described, although data are lacking for southern populations. We assessed southern mountain pine beetle oviposition rates and fecundity in a range of temperatures using a non‐destructive technique that included frequent X‐ray imaging. We found that oviposition rate and fecundity vary independently such that a female with high oviposition rate did not necessarily have high fecundity and vice versa. Observed fecundity within the 30‐day experimental period was lowest at the lowest temperature, although estimated potential fecundity did not differ among temperatures. Females at varying temperatures have the potential to lay similar numbers of eggs, although it will take longer at lower temperatures. Southern mountain pine beetle reared in Pinus strobiformis Engelm. (Pinaceae) had a higher upper threshold for oviposition, a similar lower threshold, and slightly greater potential fecundity compared to a northern population reared in Pinus contorta Douglas. A comparison of modeled oviposition rates between the two populations, which could be influenced by host tree, suggests that differences in oviposition rate do not explain observed differences in total generation time. Our oviposition model will facilitate development of a phenology model for southern mountain pine beetle populations.

Development and Dispersal of Helicoverpa zea (Lepidoptera: Noctuidae) on Non-Bt and Bt Pyramided Cotton.

Bollworm (Helicoverpa zea Boddie) (Lepidoptera: Noctuidae) can cause economic losses in both non-Bt and Bt cotton. Larvae modify their behavior in the presence of Bt by moving away from terminals faster in Bt cotton compared to non-Bt cotton and avoiding Bt-treated diets. Our objectives were to understand differences in bollworm egg and larvae populations within, and dispersal away from, non-Bt and Bt pyramided-toxin cotton. We conducted small plot experiments in 2016 and 2017 to monitor on-plant egg and larval numbers, and off-plant dispersal of larvae, from non-Bt and different Bt toxin pyramided cotton. Bollworm adults preferred to oviposit in most Bt toxin pyramids compared to non-Bt; this was likely unrelated to detection of Bt by adults, but rather density-dependent aversion from high larval populations. First instar numbers were similar in all non-Bt/Bt toxin pyramids and dispersed at a similar rate. Second through fifth instar numbers were higher in non-Bt than Bt toxin pyramids but dispersed equally from all non-Bt/Bt toxin pyramids, regardless of Bt pyramid type. Development times of larvae were often slower in Bt toxin pyramids compared to non-Bt. Fifth instars were found in, and dispersing from, Bt toxin pyramids containing Vip3A, raising concerns of resistance development. Furthermore, differences in oviposition rate among non-Bt/Bt toxin pyramids and slowed development rate of larvae on Bt varieties could create inconsistencies in generation times emerging from Bt and non-Bt hosts, which could contribute to resistance development.

Screening for Resistance Against the Sugarbeet Root Maggot, Tetanops myopaeformis (Diptera: Ulidiidae), Using a Greenhouse Bioassay.

The sugarbeet root maggot, Tetanops myopaeformis (von Röder) (Diptera: Ulidiidae), is a major pest of sugar beet Beta vulgaris L. (Carophyllales: Amaranthaceae)in the United States and Canada. Larval feeding on roots can reduce both stand and yield. Current management practices are heavily reliant on chemical control. However, the carbamate and organophosphate insecticides that are commonly used against T. myopaeformis are being phased out of use. Host plant resistance against this pest shows promise, but difficulties with maintaining T. myopaeformis in culture have largely limited such studies to the field. A primary objective of this study was to develop protocols for rearing a laboratory colony of T. myopaeformis that would expedite assays aimed at screening for host plant resistance. Third (final) instar larvae were collected from the field and reared to the adult stage. These laboratory-reared adults laid eggs and ultimately produced a second generation of third-instar larvae in the lab. Adult flies reared from field-collected larvae were used to examine the modality of resistance of a known resistant variety by performing no-choice and paired-choice experiments alongside a susceptible variety in the greenhouse. Paired-choice tests showed no difference in oviposition rates between the two varieties, whereas no-choice tests showed significantly greater feeding damage and abundance of larvae on the susceptible variety. For the resistant variety examined here, we observed evidence of antibiosis, not antixenosis, as the putative modality of resistance. Our laboratory and greenhouse protocols can be used to expedite the process of developing varieties with resistance to this key pest of sugar beet.

Context-dependent resistance against butterfly herbivory in a polyploid herb

Spatial variation in biotic interactions and natural selection are fundamental parts of natural systems, and can be driven by differences in both trait distributions and the local environmental context of the interaction. Most studies of plant-animal interactions have been performed only in natural settings, making it difficult to disentangle the effects of traits and context. To assess the relative importance of trait differences and environmental context for among-population variation in plant resistance to herbivory, we compared oviposition by the butterfly Anthocharis cardamines on two ploidy types of the herb Cardamine pratensis under experimentally controlled conditions with oviposition in natural populations. Under controlled conditions, plants from octoploid populations were significantly more preferred than plants from tetraploid populations. This difference was largely mediated by differences in flower size. Among natural populations, there was no difference in oviposition rates between the two ploidy types. Our results suggest that differences in oviposition rates among populations of the two cytotypes in the field are caused mainly by differences in environmental context, and that the higher attractiveness of octoploids to herbivores observed under common environmental conditions is balanced by the fact that they occur in habitats which harbor lower densities of butterflies. This illustrates that spatial variation in biotic interactions is the net result of differences in trait distributions of the interacting organisms and differences in environmental context, and that variation in both traits and context are important in understanding species interactions.

Host plant effects on the behaviour and performance of Amblyseius swirskii (Acari: Phytoseiidae)

Biological control in ornamental crops is challenging due to the wide diversity of crops and cultivars. In this study, we tested the hypothesis that trichome density on different host plants influences the behavior and performance of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). Behavioural observations of this predator in the presence or absence of prey (western flower thrips, Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae) were done on leaf squares of ornamental plant species differing in trichome density (rose, chrysanthemum and gerbera) and compared to a smooth surface (plastic). Tomato leaves were used to observe the influence of glandular trichomes. The performance of A. swirskii was assessed by measuring predation and oviposition rate. Behaviour of A. swirskii was influenced by plant species. Up to a certain density of trichomes, trichome number had a negative effect on walking speed. It was highest on plastic, followed by rose. No differences were found among chrysanthemum, gerbera and tomato. Walking speed was slightly higher on disks without prey. Proportion of time spent walking was the same on leaf disks of all plant species, with and without prey. No effect of glandular trichomes on tomato leaves was seen. Most thrips were killed and consumed on gerbera, and least on rose. Predation rates on chrysanthemum and plastic were intermediate. In contrast, no differences in oviposition rate were found among plant species. The results of this study indicate that trichome density can explain some of the variability in efficacy of A. swirskii on different crops. Release rates of A. swirskii may need to be adjusted depending on the crop in which it is used.

Establishment of an in vitro method for evaluating whitefly resistance in tomato.

An accurate and simple evaluation method is crucial for identifying whitefly resistance in tomato breeding. We developed an in vitro method for evaluating resistance of tomato leaves and tested this on wild and cultivated tomato varieties. We found that young leaves observed for whitefly oviposition after 8 hours provided appropriate comparative conditions. This method effectively distinguished resistance among tomato cultivars and wild species and also demonstrated significant difference in oviposition rates among leaf positions on susceptible cultivars. The in vitro test was as precise as in vivo test using intact plants and had advantages over in vivo test, and can be used for evaluating resistance in large populations.

Context dependency of nectar reward‐guided oviposition

AbstractNectar is the most common floral reward used to recruit pollination services. Changes in nectar volume may affect not only pollination services, but also the attraction of antagonists such as herbivores, especially if the same insect species acts as herbivore and pollinator. Plants compete with each other for the best pollination services, at the same time employing various strategies to avoid herbivory. Datura wrightii Regel and Nicotiana attenuata Torr. ex Watson, two sympatric solanaceous species, compete for the same hawkmoth pollinator, Manduca quinquemaculata (Haworth) (Lepidoptera: Sphingidae), although standing nectar volume per flower differs 50‐fold (70 vs. 1.3 μl, respectively) between these species. This large difference may also result in differences in oviposition rates. I conducted a detailed analysis of diurnal changes in nectar volume and sugar concentration in field‐ and glasshouse‐grown D. wrightii and N. attenuata plants, and tested how well nectar production is buffered against the loss of large amounts of foliar tissue that frequently occurs due to M. quinquemaculata larval herbivory. I examined the influence of nectar volume on herbivore damage in the field and compared the results with previously published data from N. attenuata which were collected simultaneously. Oviposition by M. quinquemaculata moths increased significantly in D. wrightii plants whose nectar volume had been experimentally increased five‐fold compared to untreated control plants, and correlated with the numbers of flowers per plant in native populations. The results suggest that a hawkmoth mother may use standing nectar volume of a potential host plant to estimate its size, and possibly health, to make the optimal decision for her progeny. This mode of assessment, however, is apparently not used with another plant species, as other more herbivory‐related cues, such as olfaction or vision, are more influential in determining oviposition rates on other plant species. Yet within a plant species, regulating nectar volume strongly influences future herbivory.

Differential susceptibility of tree species to oviposition by periodical cicadas

Abstract 1. Periodical cicadas occur widely in deciduous forests of eastern North America and represent the largest insect emergences in the world. Their effects on forest community dynamics, via oviposition damage and root feeding, are potentially great but not well understood. If tree species vary in their susceptibility to cicada oviposition and root colonization, then periodical cicadas may affect ecological interactions among tree species and forest composition.2. We measured oviposition damage on 63 tree species at 52 sites in southern Indiana, U.S.A. for two broods of periodical cicadas. We compared oviposition damage among different sites, habitats, and tree species. We also measured cicada emergence rates in mature and successional forest habitats and from beneath different tree species.3. Certain tree species received significantly more oviposition damage than others, and the most and least damaged species were consistent between the two broods. For some species, oviposition damage varied between mature and successional sites. Despite the differences in oviposition rates among species, there was no difference in emergence rates from beneath different tree species, suggesting that initial differences in cicada density among tree species are not maintained through the nymphal life cycle.4. Cicadas oviposited more at successional sites, but emerged more in mature forest stands, suggesting that successive generations of cicadas represent a shifting mosaic between forests of different ages. As tree species consistently vary in their susceptibility to oviposition damage, periodical cicadas could alter local competitive interactions and therefore affect forest dynamics.

Factors influencing adult female oviposition in the citrus leafminer Phyllocnistis citrella

1 The citrus leafminer (CLM) Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) is a serious pest in most citrus-growing regions of the world. The influence of leaf length, citrus species or variety, leaf colour tone and temperature on CLM oviposition was studied from field observations and laboratory experiments. The spatial distribution of eggs on leaves was also examined. Field data were obtained from 1100 samples collected in eastern Spain for 7 years. 2 Significant differences in oviposition rate were found among citrus species in ‘no choice’ laboratory experiments. This tendency was not apparent in the field due to the confounding effect of such factors as the intensity of new flushes and adult CLM abundance. Leaf colour tone and air temperature in the range studied (18–27°C) had no effect on CLM egg-laying. 3 The distribution of eggs among leaves was random for population densities lower than four eggs per leaf, but became strongly aggregated above this, when not all eggs could survive and complete development. 4 The CLM developmental stage found on leaves depended on the leaf length, and most of the egg-laying occurred only on leaves that were 10–25 mm long. These leaves had the highest CLM stages in the field and thus give the best estimate of CLM oviposition.

Pear sawfly (Caliroa cerasi) (Hymenoptera: Tenthredinidae) host preference and larval development on six Pyrus genotypes

The larvae of the sawfly Caliroa cerasi can cause serious damage to pear (Pyrus sp.) foliage particularly in organic or reduced‐spray orchards. Six pear cultivars and selections, three with low susceptibility to pear slug damage and three with high susceptibility, were subjected to oviposition choice tests in the field and subsequent larval development rates were monitored to clarify the nature of the variable susceptibility. Observed differences in oviposition rates corresponded with the low and high susceptibility categories of the genotypes. Larval development rates differed among genotypes and were inversely related to density of hatched eggs (a surrogate measure of leaf damage). These results confirm that host oviposition preference is a key factor influencing susceptibility to pear slug. It is further argued that feeding‐induced plant resistance and larval migration could be important factors influencing pear sawfly populations on pear trees.

Factors affecting abundance and oviposition rates of a field population of the Old World screw-worm fly, Chrysomya bezziana (Diptera: Calliphoridae).

Sentinel cattle and a grid of swormlure-baited sticky traps were used to monitor a Malaysian population of the Old World screw-worm fly, Chrysomya bezziana Villeneuve. Observations were carried out on an isolated cattle station at monthly intervals during the period August 1996 to June 2000. The number of flies caught was unaffected by weather conditions at the time of trapping, but was positively correlated with the total rainfall and the average daily air temperature prevailing 15-28 days earlier, when trapped flies were still juveniles. Trap catches were biased in favour of females, but daily catch rates of both sexes increased significantly the longer traps were open, suggesting that efficacy was related to the differential volatility of the chemicals comprising swormlure. Oviposition on sentinel cattle occurred mostly in late afternoon or early evening but increased significantly as the wound aged. Oviposition rates were positively correlated with female catch rates, but the relationship was curvilinear, suggesting that fly populations may be subject to some form of density-dependent constraint. Consistent differences in oviposition rates on sentinel cattle at different localities on the cattle station suggested the existence of highly clumped, quasi-stationary populations. Differences in trap catches between traps located in pastoral areas and those sited in nearby oil palm or rubber plantations supported this interpretation of the data. These findings are discussed in relation to the use of the sterile insect technique for the control of screw-worm fly infestations.

Eye colour as a genetic marker for fertility and fecundity of Triatoma infestans (Klug, 1834) Hemiptera, Reduviidae, Triatominae

Eye colour of Triatoma infestans is controlled at a single autosomal locus, with black-eye as the dominant gene and red-eye as the recessive. Inheritance of these characters follows a classical Mendelian system, enabling eye colour to be used as a marker for studies of mating frequency. We found no significant differences in oviposition rates and egg hatching rates irrespective of parental phenotypes. Different mating schedules between red-eye and black-eye parents showed that eye colour did not affect mating competence. Females mated with a single male or with different males together or in succession produced similar numbers of fertile eggs, with the eye colour of the offspring reflecting exposure to the different males. We conclude that although a single mating can provide sufficient sperm for the whole reproductive life of the female, multiple matings can result in balanced assortative sperm usage from the spermatheca.

Improved control capacity of the mite predator Phytoseiulus persimilis (Acari: Phytoseiidae) on tomato

The predatory mite Phytoseiulus persimilis is frequently reported to perform poorly on greenhouse tomatoes. As the predators are mass-reared on another host plant (bean), we supposed that they are poorly adapted to tomato, a plant densely packed with poisonous and sticky glandular hairs. This hypothesis was tested by comparing the control capacity of a stain of P. persimilis directly obtained from a mass rearing with the same strain after four generations on tomato. Both strains were released in a tomato crop in two identical compartments of a greenhouse and the population dynamics of prey (a tomato strain of Tetranychus urticae) and predator were recorded at weekly time intervals. It was found that the strain previously exposed to a tomato environment performed better than the unexposed strain: (1) its population increased faster; (2) the prey population declined faster; and (3) the damage to new-grown tomato leaves was considerably lower. To investigate the causes of the difference in performance between the exposed and unexposed strains, oviposition and survival rates were assessed on a diet of two-spotted spider mites on tomato leaf sections. In addition, the unexposed strain was tested on a diet of two-spotted spider mites on bean leaf sections. The difference in oviposition rates of both predator strains was small compare to the overall mean. However, the oviposition rate of the first generation of predators since transfer from bean to tomato dropped to less than half of the original value. Moreover, mortality in the first generation increased from 14% to 89%, whereas it decreased to 0% after four generations. Future research should clarify whether these changes in life history are due to selection or to physiological adaptation.

Distribution of second generation European corn borer, Ostrinia nubilalis, egg masses in field corn and relationship to subsequent tunneling damage

AbstractThe relationship between second generation European corn borer (Ostrinia nubilalis Hübner) egg mass numbers and subsequent field corn damage, as measured by stalk cavity numbers, was studied in 79 fields in northeastern North Carolina over three years. A mean of 0.028 egg masses per plant (645 egg masses/23400 plants) was found over the course of the study. Significant differences in oviposition rate were detected between fields and years. Ca. 85% of egg masses were deposited in a five leaf zone surrounding the primary ear; of these, 89% were found on the lower four leaves in this zone. Egg masses appeared to be distributed randomly within fields but at low rates of incidence, and oviposition was relatively uniform between sampling areas within individual fields. Under moderate to high oviposition pressure (mean number of egg masses per plant over the duration of the oviposition period &gt;ca. 0.02), eggs laid during the early phases of the oviposition period account for more subsequent stalk damage than eggs laid during the later phases of the oviposition period. Variations in second generation egg mass numbers accounted for ca. 70% of variation in stalk cavity numbers.

Effect of prey stage on life-table attributes of a genetically manipulated strain ofMetaseiulus occidentalis (Acari: Phytoseiidae)

Metaseiulus occidentalis females from the carbaryl-organophosphate-sulfur resistant strain (COS) lived longer (25.3 days versus 19.7 days), had a higher total fecundity (43.8 eggs female−1 versus 33.6 eggs female−1) and a higher daily fecundity rate (2.4 eggs female−1 day−1 versus 2.0 eggs female−1 day−1), and exhibited a higher intrinsic rate of increase (0.243 individuals female−1 day−1 versus 0.182 individuals female−1 day−1) and shorter generation time (13.9 days versus 17.0 days), at 24–28°C, 47–56%rh under continuous fluorescent light, when reared on a diet of 0–48-h-old eggs rather than a diet of mixed actives ofTetranychus pacificus McGregor on bean leaf disks. The sexratio of the progeny was female-biased for both diets, 2.1 females to 1 male forM. occidentalis reared on eggs and 2.0:1 ♀:♂ forM. occidentalis reared on mixed actives, suggesting that diet influences sex-ratio in some unknown way. There was no significant difference in oviposition rates for repeatedly-mated and once-matedM. occidentalis females reared on a diet of younger (0–24-h old) eggs compared to a diet of older (72–96-h old) eggs ofT. pacificus. The COS strain ofM. occidentalis exhibited life-table parameters comparable to the other strains reported in the literature, suggesting that the reproductive attributes of this acarine predator were not reduced as a result of artificial laboratory selection. Diet, a biotic factor, produced substantial differences in life-table parameters, suggesting that this factor can influence conclusions regarding the potential efficacy of biological control agents.

Oviposition Preference in Two Laboratory Colonies of Boll Weevils (Coleoptera: Curculionidae)

Oviposition preference of two laboratory colonies of boll weevils, Anthonomus grandis grandis Boheman, was measured on day-neutral (flowering response not sensitive to daylength) progenies of primitive cottons, Gossypium hirsutum L. These day-neutral cottons carry resistance to boll weevil oviposition. Rate of oviposition was used to compare the two colonies of insects. Colony 1 has been in mass production for several years without infusion of wild types. Colony 2 has not been in mass production, and wild weevils have been introduced yearly. No significant differences in oviposition rate were found between the primitive cottons and the susceptible control, ‘Stoneville 213’, when weevils from colony 1 were used for testing. Significantly fewer eggs were laid on the primitive cottons than on the control when weevils from colony 2 were tested. The long-term mass-reared boll weevil colony did not exhibit an oviposition preference; therefore, it was not suitable for use in evaluating cotton strains for differential rates of oviposition.

Pollen‐feeding and the host specificity and fecundity of flower thrips (Thysanoptera)

Abstract. 1. Flower thrips could feed on pollen of a wide range of sizes and were unaffected by exine spines. One species of thrips was unable to feed on very adhesive grains.2. The proportion of time spent feeding on each species of pollen (in seconds per minute of exposure) reflected the known host specificities. Host‐specific thrips could distinguish their host pollen, apparently without probing.3. Kakothrips pisivorus (Westwood) appeared to have a higher rate of ingestion of a host pollen than of four non‐host pollens.4. In cages in the laboratory, Thrips fuscipennis Haliday laid significantly more eggs over 48h when given pollen than when given other floral tissues or no food. K. pisivonis and Ceratothrips ericae (Haliday) also laid significantly more eggs over 48h in the presence of pollen than in its absence.5. In comparisons between pollen diets, T. fuscipennis, a generalist, laid similar numbers of eggs with each species of pollen, but K. pisivorus and C. ericae laid significantly more eggs with their respective host pollens. The differences in oviposition rate between pollen diets reflected the differences in the proportion of time spent feeding.