Host plant specificity, oviposition behaviour and egg parasitism in some leafhoppers of the genus Eupteryx (Hemiptera: Cicadellidae)

Abstract.

• 1 Three species of Eupteryx, E.aurata, E.cyclops and E.urticae are regularly found on stinging nettles in South Wales.
• 2 E.aurata host alternates between nettles in spring and autumn, and Heraclewn, Eupatorium and Mentha species in summer. E.cyclops and E.urticae attack only nettles.
• 3 All species are host specific during oviposition and show preferences to lay eggs in discrete plant regions.
• 4 A Mymarid egg parasite of the genus Anagrus was reared more commonly from eggs laid in nettles than from eggs laid in alternative hosts.

     

Selection for enemy‐free space: eggs placed away from the host plant increase survival of a neotropical ithomiine butterfly

1. The selection of an oviposition site by a phytophagous insect can depend on many factors, including the risk of predation. Many species avoid predators by laying eggs where enemies searching host plants are unlikely to find them. 2. Females of the Peruvian butterfly, Oleria onega Hewitson (Lepidoptera: Nymphalidae: Danainae: Ithomiini) lay most of their eggs (76 ± 9%) off the host plant, Solanum mite Ruiz & Pav. These off‐host eggs may be laid up to 0.5 m from the nearest host‐plant individual, on twigs or leaf litter, as well as on living plants of species unsuitable for larval food. 3. Disappearance of eggs on and off the host plant was recorded by transferring eggs laid in captivity to known locations in the wild and recording rates of disappearance before the larvae emerged. After 2 days, eggs on the host were significantly more likely to have disappeared compared to eggs laid elsewhere. 4. We conclude that a high risk of predation is a likely trigger that caused O. onega to evolve a behaviour of laying eggs off its host plant.     

The effect of a foliar disease (rust) on the development of Gastrophysa viridula (Coleoptera: Chrysomelidae)

Abstract.

• 1 Gastrophysa viridula Degeer (Coleoptera: Chrysomelidae) and the pathogenic rust fungus Uromyces rumicis (Schum.) Wint. both occur on leaves of Rumex crispus L. and R.obtusifolius L. Individual stages of beetle development, and egg laying, were compared on healthy and infected leaves of each plant species in the laboratory. Oviposition choice was investigated in the field and laboratory.
• 2 Beetles reared on infected leaves of each species had greater larval mortality and slower development than those reared on healthy leaves. Although larvae feeding on infected leaves consumed up to 2.5 times more dry weight than those reared on healthy leaves, they had a lower relative growth rate and pupated at a lower weight. These changes were consistent with the reduced nutritive quality of rust-infected Rumex leaves.
• 3 Fecundity of beetles reared on infected leaves of both species was considerably reduced. Eggs laid by beetles feeding on infected R.crispus leaves also had a reduced viability.
• 4 The beetle developed consistently poorer on healthy R.crispus than on healthy R.obtusifolius throughout its life-cycle. Differences in larval performance were greater between host species than between infected and healthy leaves.
• 5 Oviposition was similar on infected and healthy R.crispus in both the laboratory and field. However, adults consumed less, and laid fewer eggs on infected than on healthy R.obtusifolius. The pattern of egg laying on different aged leaves was affected by rust infection: a greater proportion of eggs was laid on the older, infected leaves, than on the equivalent aged leaves on the healthy plants. Few larvae survived from eggs laid on rusted leaves in the field.

     

Oviposition patterns and larval damage by the invasive horse‐chestnut leaf miner Cameraria ohridella on different species of Aesculus

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Pollen beetle (Meligethes aeneus) oviposition and feeding preference on different host plant species

The oviposition and feeding preferences of the pollen beetle, Meligethes aeneus, were determined in choice and no-choice tests in field, semi-field and greenhouse trials. Plant species used were Brassica napus, B. campestris, B. juncea, B. nigra, B. carinata, Sinapis alba and Crambe abyssinica. With respect to number of eggs laid, S. alba and C. abyssinica were inferior to the other species. Pollen beetles laid fewer eggs on B. nigra than on the other Brassica spp. in no-choice tests, however this difference was partly due to fewer eggs laid per bud rather than fewer buds used for oviposition. Most eggs, for all plant species, were deposited in buds sized 2–3 mm. Feeding damage on all plant species was relatively similar. Pollen beetles seem to have a wider host range for feeding than for oviposition. There was good agreement in plant species ranking as oviposition hosts between the field, semi-field and greenhouse trials.     

Competitive interactions and partial displacement of Anastrepha obliqua by Ceratitis capitata in the occupation of host mangoes (Mangifera indica)

1. We examined the competitive interactions between a native fruit fly species (Anastrepha obliqua Macquart) and the invasive medfly (Ceratitis capitata Wiedemann) when these co-occur on a shared mango fruit host (Mangifera indica L.).
2. Using mango fruits of distinct levels of ripeness, we investigated both competition among larvae and among adult females for oviposition. We quantified competition by the numbers of eggs laid and the intensity of agonistic interactions between adult females.
3. Interactions between immature fruit flies led to reduced size and number of emerged adults of both species. These impacts were felt more acutely in the native species.
4. Interspecific competition between females led to fewer eggs laid on semi-ripe fruit by both species, which may be the result of niche overlap associated with oviposition.
5. Intraspecific interactions between A. obliqua individuals led to intense agonistic behaviour, with a concurrent decrease in number of landings on these host fruits.
6. These results suggest that the native species undergoes a partial niche displacement when facing the invasive species. A portion of the fundamental niche of A. obliqua remained unoccupied by the invading C. capitata, which may allow their coexistence under natural conditions.

     

Host plant conspicuousness and the distribution of eggs and larvae in the butterfly,Anthocharis scolymus (Lepidoptera: Pieridae)

We investigated how the distribution pattern of eggs and larval on the host plant, Turritus glabra, was influenced by the oviposition behavior of the pierid butterfly Anthocharis scolymus. Females searched for the host plants visually and they frequently approached taller host plants with sparse surrounding vegetation. After encountering host plants, oviposition behavior of females was independent of host plant characteristics such as height, density, and type of surrounding vegetation. A female laid eggs singly on a host plants. Most females appeared to lay their eggs regardless of the presense of eggs on the host plant. Consequently egg and larva tended to be abundant on conspicuous host plants as measured by height or relative isolation from other plants. However, overcrowding of eggs on an individual host decreased the survival rate of larvae.     

Effect of host plant species of cotton whitefly Bemisia tabaci Middle East‐Asia Minor 1 (Hemiptera: Aleyrodidae) on the development,survival and reproduction of its predaceous ladybeetle Serangium japonicum (Coleoptera: Coccinellidae)

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The effect of different host plants on the reproduction and longevity of Nysius natalensis

Nysius natalensis Evans (Hemiptera: Orsillidae) is a pest of sunflower in South Africa. Adults invade sunflower fields from their weedy hosts which occur inside crop fields and on surrounding headlands. The host plant suitability for survival and reproduction as well as the effect of within‐generation host switching was studied on different wild host plants and sunflower. Life history parameters used to assess host plant suitability were F₁ adult survival, pre‐oviposition period, fecundity, and longevity. Nymphs and adults were provided with stems and seeds of five host plants, viz., Amaranthus hybridus L. (Amaranthaceae), Portulaca oleracea L. (Portulacaceae), Chenopodium album L. (Chenopodiaceae), Conyza albida Spreng. (Asteraceae), and sunflower, Helianthus annuus L. (Asteraceae). Nymphs were reared on crushed seed of the five plant species. After completion of the nymphal stage, emerging adults of each host plant group were provided with seed of a different host plant species for food. Adults did not survive long on stems only and very few eggs were laid. Seeds of the host plant species were shown to be an essential source of nutrients for N. natalensis reproduction, whereas the vegetative plant parts were unsuitable. Nymphal food and host‐plant switching between the nymphal and adult stages significantly affected the pre‐oviposition period. Nymphal and adult food source also affected female longevity. The number of eggs laid was not influenced by nymphal food, but was influenced by adult food and the switch between nymphal and adult food. The comparative attractiveness of sunflower and wild host plants for oviposition was also investigated and showed that females preferred to lay eggs on wild host plants, compared with sunflower. These results may explain why N. natalensis will lay their eggs on sunflower after weeds in the vicinity are controlled, or senesce toward the end of the growing season.     

The relationship among host plant species,egg clutch size,and level of parasitism for the sharpshooter Tapajosa rubromarginata

The sharpshooter Tapajosa rubromarginata (Signoret) (Hemiptera: Cicadellidae, Proconiini), a vector of the bacterium Xylella fastidiosa Wells et al. (Xanthomonadaceae) that causes citrus variegated chlorosis, has more than 30 reported host plant species. The fitness of a phytophagous insect is determined by the host plant suitability, plant resistance, and the natural enemies. The aim of this study was to: (1) identify plant species utilized as oviposition substrate by T. rubromarginata in the field; (2) establish the relationship between plants and clutch size; (3) establish the relationship among host plants, clutch size, and level of parasitism; and (4) establish variations in parasitoid composition and abundance in the various host plants. Egg masses of the sharpshooter were surveyed on plants reported as hosts, or those that were abundant in the study site. The number of eggs of the sharpshooter and emerged parasitoids were recorded for all the collected masses. We found egg masses of T. rubromarginata on 12 out of 21 plant species sampled. The size of the egg masses was greatly influenced by the type of leaf venation and to a lesser extent by the plant species. Parasitism rates were influenced by both leaf venation and host plant. Trichogrammatidae species were mostly associated with egg masses in plants with parallel-veined leaves, whereas Mymaridae attacked masses laid in reticular-veined leaves. The choice between a good host plant, but heavily attacked by parasitoids, and the host plants that are less suitable for nymphs but less frequently attacked by natural enemies, was a trade-off for T. rubromarginata females to increase their fitness. We conclude that the host plant utilization by T. rubromarginata females in the field could be influenced by leaf structure and the strategy to avoid parasitism by selecting plants that were less attractive for parasitoids.     

Climate,landscape, habitat,and woodland management associations with hazel dormouse Muscardinus avellanarius population status

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VARIATION IN PREFERENCE AND SPECIFICITY IN MONOPHAGOUS AND OLIGOPHAGOUS SWALLOWTAIL BUTTERFLIES

Although variation in oviposition preference and specificity for host plants has been demonstrated within populations of a variety of oligophagous insect species, it is unknown whether genetic variation in host choice is lost within populations of monophagous species. Analysis of a locally monophagous butterfly species, Papilio oregonius, and a locally oligophagous species, P. zelicaon, showed significant variation in oviposition preference within populations of both species. Females of both species chose primarily their native hosts. Nonetheless, the percentages of eggs laid by individual females among the plant species and the number of plant species on which individual females laid eggs differed significantly among isofemale strains within populations. Moreover, some females within all isofemale strains of both species laid a few eggs on Foeniculum vulgare, an umbelliferous species that does not occur in the native habitats of these populations but is a host for Papilio species in other geographic areas. The results suggest that local monophagy and oligophagy in these species reflect the relative ranking among potential plant species. Both populations harbor variation in oviposition choice that could allow for host shifts if these populations invaded new habitats.     

The effect of cold temperature exposure and long-day photoperiod on the termination of the reproductive diapause of newly emerged female Pissodes strobi (Coleoptera: Curculionidae)

Abstract

• 1 There is confusion in the literature concerning a possible reproductive diapause in the adult white pine weevil Pissodes strobi.
• 2 We evaluated the effects of temperature, photoperiod, feeding substrate and mating status on the sexual maturation and oviposition of female white pine weevils.
• 3 Less than 30% of female P. strobi became sexually mature and laid eggs without experiencing dormancy under a temperature regime of 2 °C for 4 weeks.
• 4 Among the females that experienced a cold temperature treatment after emergence, 80% laid eggs after dormancy when exposed to a long‐day (LD 16 : 8 h) photoperiod and 17.6% laid eggs when exposed to a short‐day (LD 8 : 16 h) photoperiod.
• 5 Significantly more eggs were laid by all the females (with and without a cold treatment) when subjected to a long‐day photoperiod compared with a short‐day photoperiod.
• 6 A period of cold temperature followed by exposure to a long‐day photoperiod with warmer temperatures is required to break reproductive diapause and to obtain a good oviposition response in female P. strobi.
• 7 This study reveals the existence of much intraspecific variation in the response of the white pine weevil to temperature and photoperiod with respect to the induction and termination of reproductive diapause.

     

Essential oil composition in leaves of carrot varieties and preference of specialist and generalist sucking insect herbivores

• 1 The carrot psyllid Trioza apicalis and Lygus rugulipennis can cause serious damage to cultivated carrots, especially at the seedling stage. The essential oil composition in leaves of several carrot varieties was studied in relation to oviposition acceptance by sucking insect herbivores that have different feeding strategies. Of the insect species studied, T. apicalis is a carrot specialist, T. anthrisci is an Apiaceae specialist, and L. rugulipennis is a generalist.
• 2 The oil composition differed significantly between leaves from different carrot varieties (Flakkeer 2, Nantura, Parano, Napoli, Panther, Splendid, Nantes 3 Express).
• 3 There were no differences in the mean numbers of eggs laid by T. apicalis or T. anthrisci on different varieties, but L. rugulipennis laid fewer eggs on the Panther variety than on Nantes 3 Express.
• 4 There was a negative linear correlation between limonene concentration and number of eggs laid by T. apicalis, confirming that limonene is a repellent to the carrot psyllid. Results suggest that only particular compounds influence the preference of the carrot psyllid, and these compounds may not be the main components in the essential oil of carrots.
• 5 A positive correlation was found between myrcene concentration and number of eggs laid by T. anthrisci. Essential oil composition did not explain egg‐laying preference of L. rugulipennis.
• 6 The results indicate that essential oil composition of carrot varieties affects host preference of Apiaceae specialists more than that of generalists.

     

Egg size manipulation in the migrant skipper, Parnara guttata guttata (Lepidoptera: Hesperiidae), in response to different host plants

Female adults of the migrant skipper, Parnara guttata guttata, lay different-sized eggs on different host plants in different generations. Moreover, P. g. guttata maintains large egg size variation either in the population or in the individual. Why such phenotypic plasticity in egg size is maintained has not been clarified. In the present study we performed a series of experiments to verify whether or not females of P. g. guttata discriminate between the different host plants, i.e., rice plant Oriza sativa in the first and second generations and cogon grass Imperata cylindrica in the third (overwintering) generation and manipulate egg size accordingly on these host plants. When a caged female was allowed to lay eggs alternatively on soft-leafed rice plant and tough-leafed cogon grass, the size of the eggs laid on cogon grass was significantly larger than that on rice plant. When a caged female was allowed to lay eggs on the two host plants that were supplied on alternate days, the size of eggs laid on cogon grass was also significantly larger than that on rice plant. A preliminary experiment using crude extract from the plants suggested that females did not manipulate egg size in response to chemical stimulants alone. The skipper female was able to lay different-sized eggs instantaneously after assessing the host plant. However, the reaction norm to different host plants differed among females. Eggs of various sizes were matured in each ovariole, and egg size variation at the lowest part of the ovariole ranged from the size of the larger eggs laid on cogon grass to that of the smaller eggs laid on rice plant, although how the female chose the appropriate-sized egg at each occasion is unknown.     

Nocturnal activity and resource utilization in the aphid hyperparasitoid, Dendrocerus carpenteri

Abstract.

• 1 Females of the aphid hyperparasitoid Dendrocerus carpenteri (Curtis) search successfully for hosts during both day and night. Oviposition numbers per host patch did not differ significantly between day and night.
• 2 D.carpenteri females also displayed a nocturnal flight activity, showing that they are not only capable of searching on a given host plant but also of dispersing between host plants.
• 3 Nocturnal oviposition activity was mainly influenced by egg load. Females with a high egg load laid more eggs at night than females with a comparatively low egg load. Thus, D.carpenteri females may use nocturnal foraging to compensate for the lack of oviposition opportunities during day.
• 4 D.carpenteri females which foraged continuously for hosts both day and night (= for 24 h per day) benefitted from an 1.4-fold increase in lifetime reproductive success when compared to females which foraged only by day (= for 16 h per day).
• 5 The benefit of night foraging for this species is a significantly increased reproductive success.

     

Conserving a wetland butterfly: quantifying early lifestage survival through seasonal flooding, adult nectar, and habitat preference

Conservation of once thought extinct populations of Lycaena xanthoides in western Oregon will require specific information of how the butterfly interacts with its now rare wetland habitat. Three experiments were conducted to yield information directly applicable to wetland restoration work: (1) to quantify the survival of L. xanthoides eggs laid on inundated plants, (2) to quantify adult nectar preferences, (3) to investigate the role of adult resources and how butterflies assess habitat quality. Survival of eggs laid on inundated plants was nearly seven times lower than the survival of eggs laid on uninundated plants, indicating that eggs laid on plants that are seasonally flooded are a population sink. Adult L. xanthoides preferred an endemic native nectar plant, Grindelia integrifolia × nana, as an adult resource and used it approximately 88% of the time while other butterfly species preferred to nectar on the non-native Mentha pulegium. Adult L. xanthoides had a significantly greater short-term recapture rate in two restored study sites that had a high relative amount of Grindelia integrifolia × nana compared to a degraded site that lacked the preferred nectar source. Based on the results from the three small experiments, restoration of wetlands for L. xanthoides should concentrate plantings of host plant in non-flooded areas and propagate conspicuous patches of the preferred nectar plant.     

The population biology of the Orange Tip butterfly Anthocharis cardamines in Britain

ABSTRACT.

• 1 The population biology of Anthocharis cardamines (L.) is described and shown to vary with locality. Southern and Western populations emerge earlier than Northern ones, but Western and Northern populations occupy similar, wetter habitats and are associated primarily with Cardamine pratensis (L.). Southern populations are recorded mostly from Alliaria petiolata (Bieb.).
• 2 Studies on egg and larval survival indicate that host plant-induced death and parasitization by a tachinid are important mortality factors. However, a key-factor analysis on one population indicates that the major determinant of population size may be the number of eggs laid by ovipositing females, itself dependent upon weather during the oviposition period. Populations in different localities do show similar trends in abundance, corroborating the effect of weather.
• 3 Human effects on distribution and abundance are discussed, and some conservation strategies suggested.

     

Diversity and distribution patterns of some mesophyll-feeding leaf hoppers of temperate woodland canopy

• 1 Temperate woodland canopy as a habitat for insects is discussed.
• 2 A general account is given of the Typhlocybinae as the mesophyll-feeding guild of canopy feeders.
• 3 Three sampling sites in South Wales are described, from which adult leaf-hoppers were sampled regularly from twelve species of trees during 1974.
• 4 Rearing records, based on the sampling of last instar nymphs and subsequent rearing of adults, are given.
• 5 Over 20 000 adult insects of thirty-five identified species were taken during 1974.
• 6 Results are analysed to compare species associations with different tree species. Most leaf-hoppers show very distinct specific plant-dependent distributions within the canopy. Many are dominantly associated with only one host plant. Others show more complicated patterns of associations. Only one species was found on all trees sampled.
• 7 The patterns of leafhopper distributions in woodland canopy are compared with previously described grassland habitats. The relative permanence and size of trees may be important factors.
• 8 Examples of groups of ecologically similar species coexisting together are discussed.

     

The influence of intraguild competitors on reproductive decisions by two predatory Heteroptera,Orius insidiosus (Anthocoridae) and Nabis americoferus (Nabidae)

The relationship between the oviposition site preferences of predators in the face of intraguild competitors has received little attention, but it likely shapes the reproductive ecology of predatory species. In this study, oviposition intensity and the within-plant distribution of Orius insidiosus (Heteroptera: Anthocoridae) and Nabis americoferus (Heteroptera: Nabidae) eggs on Phaseolus vulgaris plants was studied when the two species were present independently or in combination. Both predators laid more eggs in the presence of the other species relative to when they were only exposed to conspecifics. When only exposed to conspecifics, O. insidiosus preferred to lay eggs on leaves and petioles on the upper half of the plant, whereas N. americoferus laid eggs mostly on the petioles and petiolules equally throughout the height of the plant. But when both species were present, O. insidiosus preferred to lay eggs on the leaf, whereas N. americoferus altered their behavior to lay an even greater proportion of their eggs on the petioles and petiolules. They altered their preferences for different plant strata too: N. americoferus laid more eggs on the upper quarter of the plant when O. insidiosus was present, and O. insidiosus was marginally more likely to lay eggs lower on the plant in the presence of N. americoferus. This study indicates that these two Cimicomorpha can detect the presence of one another, and that they adjust their reproductive decisions, presumably to avoid potential competitive interactions.