Host preferences of the cocoa pod borer,Conopomorpha cramerella,the main threat to cocoa production in Southeast Asia

Insects ensure the survival of their offspring by depositing their eggs in suitable environments. Even generalist egg-laying insects often show preferences for specific host plants. The cocoa pod borer (CPB), Conopomorpha cramerella (Snellen) (Lepidoptera: Gracillariidae), successfully infests and reproduces on relatively few host plants, but has a major economic impact only on cocoa, Theobroma cacao L. (Malvaceae). Choice tests were performed in the laboratory to compare the frequency of insect visits, the duration of the visits, and the number of eggs laid on the fruits for each combination of host plants tested – that is, cocoa clones or fruits of rambutan (Nephelium lappaceum L.), Fijian longan (Pometia pinnata JR Forst & G Forst, both Sapindaceae), and langsat (Lansium domesticum Corrêa, Malvaceae). Our laboratory study showed that, when given the choice, CPB significantly favored cocoa pods over other host fruits (rambutan, langsat, or Fijian longan). Females also deposited more eggs on unripe fruits than on ripe fruits of similar size. The preference to lay eggs on specific cocoa clones in the bioassays did not reflect the level of the clone resistance to CPB damage reported from the field. Consequently, oviposition preference of female CPB does not seem to be the main factor explaining field resistance of some cocoa clones to CPB infestation.     

Oviposition choice by the Onopordum capitulum weevil Larinus latus (Coleoptera: Curculionidae) and its effect on the survival of immature stages

Female Larinus latus lay eggs into the capitula of their Onopordum spp. host plants from the onset of capitulum development until the completion of flowering. This tight linkage between insect life-history and plant development optimised larval survival, apart from some initial asynchrony between the readiness of the females to oviposit and the suitability of the very small capitula to physically support eggs. Eggs were laid on bracts and stems of capitula or directly in the florets, when these became available. Both the location of the egg and time of oviposition influenced mortality factors such as egg and larval parasitism, egg desiccation and larval establishment. Overall, survival of eggs laid later in the season into florets was higher, although the adults that emerged were smaller. The change in choice of oviposition site that occurs at the onset of flowering, not only favours survival, but ensures more efficient resource use by the larvae. This occurs because sequential flowering of Onopordum spp. drives a sequential oviposition pattern and spreads the egg load more evenly over the available capitula, reversing a trend earlier in the season to clump eggs that were laid directly on the bracts. Other potential constraints, such as capitulum size, absolute egg density and previous egg-laying do not play a major role in determining the oviposition pattern of L. latus. Larval survival was positively correlated with capitulum size and not strongly influenced by egg density. Competition for resources only appeared to play a role in smaller capitula, and manifested itself in a reduction in the size of emerging adults rather than the death of immatures. In the absence of strong interspecific competition, the oviposition behavior of L. latus has become geared to maximising resource use for larvae (i.e. its own potential competitiveness) rather than minimising interactions with other members of the capitulum endophage guild.     

Additive inheritance of resistance to pod rot caused by Phytophthora palmivora in cocoa

Summary Quantitative inheritance of resistance to Phytophthora pod rot (Ppr) was studied in cocoa hybrid progeny from 12 Trinitario x Amazonian crosses and their reciprocal crosses. The crossing scheme was similar to a factorial design. Disease was assessed by the number and percentage of infected pods on each tree. Highly significant differences due to general combining abilities (GCA) were obtained for all characters, except for the GCA of Trinitario on total pod production. Differences for specific combining ability (SCA) were not significant for all characters. There were no significant differences between reciprocal crosses. The Trinitario clone K82 provided the only source for the hybrid progenies of strong Ppr resistance to the hybrid progenies, while K20 provided moderate resistance. Other parental clones — KA2-101, KA5-201, KEE 2, KEE 5, and KEE 52 — produced progenies which were susceptible to Ppr. It is evident that resistance to Ppr in cocoa is inherited additively. Maternal and cytoplasmic effects were assumed to have no influence on inheritance of resistance. It is also concluded that resistance to Ppr of the kind shown by K82 is likely to be horizontal resistance. Breeding for high-yielding cultivars combined with Ppr resistance is the most effective way of controlling Ppr of cocoa on the crops of growers with small holdings in Papua New Guinea.     

Female's preference for oviposition site and larval performance in the water-lily beetle,Galerucella nymphaeae (Coleoptera: Chrysomelidae)

Water-lily beetles prefer younger rather than older water-lily leaves as oviposition sites. By the time of hatching, however, young leaves have aged consieerably. Larval performance of the water-lily beetle was measured on different types of leaves of the yellow water-lily and compared with oviposition preference of females. The leaf types used in the experiments were categorized as (i) young, (ii) natal (medium-aged) and (iii) old. The natal leaves were the ones on which larvae from a particular egg-batch had hatched. There were two sets of experiments. First, larvae were raised from eggs to pupae on young and on old leaves. Second, the growth of the 1st-instar larvae was measured on young, natal, and old leaves. The development time from egg to pupa did not differ between young and old leaves, but larvae growing on young leaves attained a higher pupal weight. In the second experiment the 1st-instar larvae grew fastest on their natal leaves, but there was also variation in the growth rate of progeny from different egg-batches. Larval growth on young and old leaves did not differ significantly. Larvae tried to emigrate much less from natal than other types of leaves. Females tended to lay eggs on leaves where larval growth was fastest. It seems that medium-aged leaves are best for larval growth, but the leaf characteristics responsible for this remain unresolved.     

Oviposition preferences and larval performance of a flower-feeding weevil,Coelocephalapion aculeatum, in relation to host development

The oviposition behaviour ofCoelocephalapion aculeatum Fall (Coleoptera: Apionidae), a host specific florivore exploiting an ephemeral resource, was studied in relation to host development. Immature inflorescences of its host, the weedMimosa pigra L. (Mimosaceae), were categorised into 5 developmental stages ranging from first appearance to one day before opening. The duration, weight, percent abortion, and nitrogen content of each stage were measured. Oviposition preferences ofC. aculeatum for all inflorescence stages were determined in multiple choice trials. Newly hatched, larvae were transferred into inflorescences of each stage to determine larval survival as a function of stage. Numbers of eggs laid into inflorescences generally correlated with larval survival except that oviposition was greater in stage 4 inflorescences than expected from the larval survival. Numbers of eggs laid into inflorescences generally correlated with their carrying capacity except that adults avoided stage 5 inflorescences in which larval survival was low. The evolution of oviposition preferences ofC. aculeatum appears to have been influenced by two opposing selective forces. The need to complete development before the inflorescence deteriorated would have selected for oviposition in young inflorescences. The greater availability of food and lower probability of abortion offered by older inflorescences would have selected for oviposition in these. The net outcome of these pressures has resulted in the observed oviposition strategy.     

Risk to non-target plants from Charidotis auroguttata (Chrysomelidae: Coleoptera), a potential biocontrol agent for cat’s claw creeper Macfadyena unguis-cati (Bignoniaceae) in Australia

The potential of the leaf beetle Charidotis auroguttata as a biocontrol agent for cat’s claw creeper Macfadyena unguis-cati (Bignoniaceae), an environmental weed in Australia, and risk to non-target plants was evaluated under quarantine conditions. In no-choice tests, C. auroguttata adults and larvae fed on many plant species across different families, but egg to adult development occurred only on the target weed. However, when neonate larvae from the target weed were transferred onto Myoporum boninense australe (Myoporaceae), a non-target native plant, 11.7% completed development, as compared to 95% of larvae that completed development on the target weed. Larval development on this non-target species also took twice as long as on the target weed. No larvae completed development on other test plants. In choice tests, leaf area consumption by adults and larvae was significantly more on the target weed than on other plants, and oviposition occurred only on the target weed. In the no-choice demography trials, adults laid eggs from the second week after emergence on the target weed, with an average of 0.286 eggs/female/day, resulting in an 18-fold increase in the adult population over 16 weeks. On My. boninense australe adult survival remained high, but oviposition commenced only from the 10th week after emergence with an average of 0.023 eggs/female/day, and none of the eggs developed into adults. In the choice demography trials, oviposition on the target weed was evident from the fourth week onwards, while on the non-target plant oviposition commenced only from the 14th week. Only 10% of total adults and 11.3% of total eggs were found on the non-target plant, and none of these eggs developed into adults. Although the biocontrol agent can ‘spill-over’ from the target weed to the non-target native plant and cause adult feeding damage, the non-target plant could not sustain a viable insect population on its own. This agent was not approved for field release in Australia due to perceived risk to non-target species.     

Cocoa-based media for culturing Phytophthora palmivora (Butl.) Butl., causal agent of black pod disease of cocoa

Green cocoa pod husk agar (GCPA), ripe cocoa pod husk agar (RCPA), green cocoabean agar (GCBA), ripe cocoa bean agar (RCBA), green cocoa mucilage agar (GCMA)and ripe cocoa mucilage agar (RCMA) were prepared and assessd for their clarity andfor potential to support mycelial growth and sporulation of P. palmivora. Oatmeal agar (OMA), potato-dextrose agar (PDA), vegetable 8 juice agar (V8JA) and pineapple crown agar (PCA) were included for comparison. The highest radial growth rates of 8.3 and 7.2 mm/day were recorded, respectively, on OMA and GCPA but these were not significantly different (P ≤ 0 05) from each other. The two media also supported good aerial mycelial growth but were not clear. Radial mycelial growth rates of 6.5, 7.0 and 6.6 mm/day were obtained on GCMA, RCPA and V8JA, respectively, and these rates were also not significantly different from each other. Of the three media, only the GCMA was clear and supported the best aerial mycelial growth. In comparison, the RCMA supported a significantly lower radial growth (4.6 mm/day) of P. palmivora than the three media. Growth rates were least on RCBA, PCA and PDA but sporulation was poorest on PDA, PCA and V8JA. GCMA was found to be the best medium based on all the growth parameters and media characteristics. GCMA has been used effectively to isolate/detect P. palmivora from infected cocoa pod tissues. Apart from differences in radial growth rate, both the GCMA and RCMA were similar in all other respects and are recommended for culturing P. palmivora. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of cowpea pod maturity on the oviposition choices and larval survival of a bruchid beetle Callosobruchus maculatus

The active or dispersing morph of Callosobruchus maculatus, a pest of stored cowpeas, is presumed to infest cowpea plants in the field prior to harvest. In oviposition choice tests, both normal and active females preferred pods that were full-size but still green over younger, smaller pods or older, mature pods. Exposed seeds were usually preferred over intact pods of all stages, although females laid more eggs on green pods than on the rough-coated seeds of one cowpea variety. Egg-to-adult survivorship was highest for eggs laid directly on seeds. On both green and mature pods high mortality occurred because newly hatched larvae failed to penetrate a seed after they drilled through the pod wall. However, since 20–50% of eggs laid on green pods do develop into adults, cowpea plants are susceptible to C. maculatus well before pods dehisce to expose the seeds. The oviposition preferences of C. maculatus may be strongly influenced by the surface texture of potential oviposition sites.

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Résumé La forme active de Callosobruchus maculatus, ennemi de Vigna unguiculata stocké, est suspectée d'infester les gousses dans les champs avant la récolte. Lors d'essais sur le choix du lieu de ponte, toutes les femelles, normales et actives, ont préféré les gousses encore vertes mais ayant atteint leur taille définitive aux gousses plus jeunes ou aux gousses plus âgées (jaunes) ou mûres. Les graines étaient presque toujours préférées aux gousses à tous les stades, mais quand les graines étaient rugueuses, elles pondaient de préférence sur les gousses vertes.Le pourcentage le plus élevé d'adultes a été obtenu à partir des oeufs pondus sur les graines. Avec les pontes sur gousses vertes ou mûres, la mortalité élevée se produisait lors de la pénétration dans la gousse. Néanmoins, comme 20 à 50% des oeufs pondus sur des gousses vertes donnent des adultes, V. unguiculata est susceptible d'être attaqué par C. maculatus bien avant la déhiscence des gousses et l'exposition des graines. L'évolution temporelle des propriétés physiques des gousses paraît à l'origine de la relation complexe entre l'âge et l'attractivité des gousses.

     

Resistance to the cowpea weevil (Callosobruchus maculatus) larva in pods of cowpea (Vigna unguiculata)

Thirty cowpea, Vigna unguiculata (L.) Walpers, cultivars were evaluated as intact pods to determine if any possessed resistance to the cowpea weevil, Callosobruchus maculatus (Fabr.). Pod resistance was measured as pre-establishment larval mortality (PreM); those larvae dying after egg hatch but before penetrating into the seeds, and as post-establishment within-seed mortality (PostM); those larvae dying after penetrating into the seeds. Among the 30 varieties examined, PreM ranged from 57.9% to 99.4% and PostM ranged from 6.7% to 82.6%. Ten varieties exhibited total intact pod mortality (mortality from egg hatch to adult emergence from the seed) greater than 95%.Physical measurements were made of several pod and seed characteristics to ascertain whether the observed pod resistance was due to seed factors, pod-wall factors, or to interactions between the pod and seeds. Although resistance to breakage (from handling plus pod dehiscence) is a necessary characteristic for overall pod protection against C. maculatus; other factors are also important. Among the other pod and seed characteristics measured to identify major resistance factors, seed coat thickness was the one most highly correlated with pod resistance. Our results suggest that interactions between pod-wall and seed coat characteristics play a large role in pod resistance of cowpeas to C. maculatus.     

The problem of optimal clutch size in a tritrophic system: the oviposition strategy of the thistle gallfly Urophora cardui (Diptera,Tephritidae)

The problem of optimal clutch sizes is a central theme in life history theory. Optimal allocation of eggs is especially complicated for insects in tritrophic systems. In this study we analyze some of the processes determining clutch sizes of the thistle gallfly Urophora cardui, a monophagous tephritid fly associated with Cirsium arvense. U. cardui forms multilocular shoot galls, which vary broadly in their size and number of their gall cells. We investigate various fitness consequences of gall size. An analysis of the number of cells per gall (which is correlated with gall diameter and gall weight) showed that in U. cardui there is mutual facilitation rather than larval competition. Increasing numbers of larvae per gall led to a decreasing mortality and increasing larval weight. Larval weight in turn was positively correlated with the probability of survival to adulthood and with adult weight and fecundity. Thus, all fitness parameters measured favoured large galls. Clutch sizes in oviposition experiments were distinctly larger than the number of gall cells of field populations and in cage experiments, suggesting high mortality of eggs and/or early larval instars. There was a significant relationship between the internal structure (i.e., the size of the growing point) of the bud and clutch size, suggesting that U. cardui females are able to measure bud quality and adapt clutch sizes accordingly. Clutch size was positively correlated with the female's age at first oviposition and negatively with the number of previous ovipositions and previously laid eggs. Since the potential egg capacity per female is higher than the average number of larvae it is likely to produce during its short adult lifespan, U. cardui females tend to be time-limited rather than egglimited, which might favour large clutches once an appropriate oviposition site has been located. As the development of the gall and hence the fate of a clutch depends on a number of unpredictable factors, exclusive concentration of eggs in a few large clusters would involve risks which could be avoided by increasing the number of clutches. Therefore we interpret the high variation of clutch sizes in U. cardui as a mixed strategy of bet hedging and gambling.     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

Electrophoretic protein patterns of three species ofPhytophthora associated with black pod disease of cocoa (Theobroma cacao L.)

When electrophoretic profiles of native proteins from vegetative mycelia ofPhytophthora palmivora, Phytophthora capsici and Phytophthora citrophthora causing black pod disease of cocoa in India were compared on a single Polyacrylamide gel, the isolates of same species were readily distinguished both qualitatively by visual similarity in banding patterns and quantitatively by calculating similarity coefficients. Similarity coefficients were generally much higher between isolates within a species than between isolates of different species. The dendrograms obtained after unweighted pair grouping with arithmetic averaging cluster analysis, revealed that all the isolates ofPhytophthora capsici were highly homogenous and formed a single cluster. The isolates ofPhytophthora citrophthora were resolved into two electrophoretic types which were clustered into two distinct sub groups.Phytophthora palmivora formed a separate group. Thus, the results reveal that polyacrylamide gel electrophoresis can be used successfully in distinguishing species and sub groups within a species ofPhytophthora encountered on cocoa. CPCRl contribution No. 914.     

Influence of induced water stress in ponderosa pine on pine sawflies

Summary Three levels of water stress were induced on pole-size ponderosa pine (Pinus ponderosa) to determine the influence of plant moisture stress on oviposition, survival, and growth of two species of pine sawfly (Neodiprion fulviceps and N. autumnalis). It was found that water stress affected oviposition and subsequent egg survival but not larval development or survival. Stress had a negative effect on early season oviposition (N. fulviceps) and a positive effect on late season oviposition (N. autumnalis). Egg hatch was different between species and years and among treatment levels. Larval development, feeding, and survival were not affected by water stress. Overall, the effect of stress was not sufficient to explain population outbreaks of sawflies. Several hypotheses are presented as possible explanations for the observed experimental results.     

An experimental study of population regulation in the salamander,Notophthalmus viridescens dorsalis (Urodela: Salamandridae)

Summary The roles of density-dependent larval survival and cannibalism of larvae as potential mechanisms of population regulation in the newt (Notophthalmus viridescens dorsalis) were evaluated in laboratory and field experiments. In laboratory containers, adults cannibalized larvae and large larvae cannibalized smaller larvae. In artificial ponds, larval survival did not depend on initial larval density. No cannibalism could be demonstrated in the complex environment, although the experiment was powerful enough to detect an ecologically relevant difference in survival. Adult growth was negatively correlated with the final biomass of larval newts, suggesting that the two life stages competed for resources. Larval growth rates were negatively correlated with final larval density, suggesting that larvae competed with each other. The proportion of larvae that became sexually mature at age 7 months (paedomorphs and adults that skipped the eft stage) varied inversely with larval density. Therefore, the potential regulatory mechanisms identified in this study are competition within and between life stages.     

Imperfect oviposition decisions by the pitcher plant mosquito (Wyeomyia smithii)

Summary Wyeomyia smithii mosquitoes distribute their eggs across available oviposition sites (water-holding pitcher plant leaves) of varying quality. I experimentally examined responses to three components of site quality: conspecific larval density, larval density of the pitcher plant midge,Metriocnemus knabi, and pitcher size. Responses to larval treatments were complex and apparently suboptimal. Although mosquito larval performance is better in leaves with fewer conspecific and more midge larvae, females did not lay more eggs in such pitchers. Instead, more eggs were laid in experimental pitchers containing either midge or mosquito larvae, but fewer eggs in pitchers with neither or both. More eggs were laid in larger pitchers, which tend to accumulate more resources and dry out less often. Therefore, although the oviposition decisions made were suboptimal, they were better than random.     

Potential for biological control of tent building species of ants associated with Phytophthora palmivora pod rot of cocoa in Papua New Guinea

The tents of different ant species collected from young cocoa trees in their first or second year of bearing and free from visible pod rot, were tested for the presence of Phytopthtora palmivora by inoculating wounded cocoa pods with tent material. Tents of all species harboured viable P. palmivora but those consisting mainly of soil were more frequently positive than plant debris-type tents. Although Anoplolepis longipes, a dominant, ground nesting, non-tent building species sometimes transported inocula in the laboratory, it did not significantly increase black pod infection in the field. Trees infested with the dominant debris tent building species, Technomyrmex albipes, however, had significantly more black pod than those infested with A. longipes or trees without ants. A. longipes forms dense populations and can exclude other dominant ants and some cocoa pests; its introduction may be a potentially economical method of reducing the transmission of P. palmivora in redeveloped cocoa in Papua New Guinea.     

Geometric isomers of sex pheromone components do not affect attractancy of Conopomorpha cramerella in cocoa plantations

The cocoa pod borer (CPB), Conopomorpha cramerella (Snellen), sex pheromone was previously identified as a blend of (E,Z,Z)‐ and (E,E,Z)‐4,6,10‐hexadecatrienyl acetates and corresponding alcohols. These pheromone components were synthesized by modification of an existing method and the relative attractiveness of synthetic blends that included different levels of non‐target pheromone components and chemical purities was tested in a cocoa field using Delta traps. Male captures were not significantly different among traps baited with pheromone blends containing 5% to 47% (based on four identified pheromone components) of other geometric acetates [(E,Z,E)‐, (Z,Z,Z)‐, (Z,E,Z)‐ and (Z,E,E)‐4,6,10‐hexadecatrienyl acetates], indicating that C. cramerella males did not discriminate among the pheromone components and other geometric isomers in the blends. Therefore, neither antagonistic nor synergistic effects from other pheromone geometric isomers were observed. The modified synthetic pathway offers the prospect of more economical production of CPB sex pheromone. During 17 weeks when C. cramerella monitoring coincided with the main cocoa pod harvest period in 2013–2014, CPB trap catch data from some blends showed a good correlation with the number of pods with C. cramerella infestation symptoms.     

Biology of Anagrus atomus (Hymenoptera: Mymaridae), an egg parasitoid of the grape leafhopper Arboridia kermanshah (Homoptera: Cicadellidae)

Biology, morphology and oviposition behavior of Anagrus atomus (Linnaeus), an egg parasitoid of the grape leafhopper Arboridia kermanshah Dlabola in Isfahan, Iran, were investigated. Adults were smaller than those so far reported from other regions. Females continuously drummed on plant surfaces with their antennae to search for host eggs. Parasitoid eggs hatched 2–3 days after oviposition, and A. atomus had two larval instars. First instar larvae were sacciform and immobile. Second instar larvae appeared 4 days after oviposition and were very active, and doubled their body length. The prepupal and pupal stages lasted for 1 and 5–6 days, respectively. Adult emergence began 16 days after oviposition, and peaked on day 17.     

Influence of initial egg density and host size on the development of the gregarious parasitoid <Emphasis Type="Italic">Bracon hebetor</Emphasis> on three different host species

Bracon hebetor (Say) (Hymenoptera : Braconidae) is a gregarious parasitoid that attacks a variety of important lepidopterous pests of stored product and in the field. In this study the effect of host species, size and larval competition on parasitoid size, survival and development were investigated. In laboratory studies, wasp eggs at a range of densities, were placed on larvae of different weight of three Lepidoptera host species namely Adoxophyes orana (Fischer von Röslerstamm, Tortricidae), Plodia interpunctella (Hubner, Pyralidae) and, Lobesia botrana(Dennis & Schiffermueller, Tortricidae). On A. orana survival of immature parasitoids was very low at all densities and different host weights. On L. botrana survival progressively reduced as egg density increased at both host weights examined for this host. Survival on P. interpunctella was significantly affected by egg density but not by host weight. Initial egg density had a significant effect on the size of emerging adults from each rearing host. Smaller adult parasitoids emerged as egg density per larva increased. Larval host weight of P. interpunctella and A. orana had a significant effect on the size of emerging adult parasitoids mainly at the higher egg densities used in these experiments. The above results of host quality on fitness of parasitoid are discussed.     

Are gardens effective in butterfly conservation? A case study with the pipevine swallowtail, <Emphasis Type="Italic">Battus philenor</Emphasis>

Gardens with nectar sources and larval host plants have been proposed to stem the decline in butterfly abundance caused by habitat loss. However, no study has provided evidence that gardens benefit butterflies. We examined the use of natural sites and gardens in the San Francisco bay area by the butterfly, Battus philenor. We found that natural sites were more likely to attract adult B. philenor, received more oviposition, and had higher juvenile survival than gardens sites. Butterflies were more likely to be present in gardens with established populations of the host plant, Aristolochia californica, growing in the sun. Battus philenor are unlikely to visit gardens with host plants planted within the past 7 years. Gardens between the ages of 8–40 years received oviposition, but did not always support completion of larval development of B. philenor. In gardens with host plants over 40 years of age, B. philenor consistently survived from egg to the adult stage. Natural enemy induced mortality of eggs did not differ between garden and natural sites, but overall egg survival was lower in gardens than at natural sites. It is unlikely that gardens serve as 'refugia' for B. philenor in years when populations in natural sites experience low survival or low fecundity. Even in gardens capable of supporting larvae to maturity, the density of eggs and survival rates were lower than in natural populations of the host plant suggesting that gardens were not optimal habitats. Therefore, without evidence that juvenile abundance and survival rates in gardens matches or exceeds that in natural sites, it is most likely that gardens act as population sinks for B. philenor.