Native Host Plants Research Articles

Native Hymenopteran Parasitoids Associated with Anastrepha spp. (Diptera: Tephritidae) in Seropedica City, Rio de Janeiro, Brazil

Parasitoids associated with five species of Anastrepha were recovered from host fruits that belong to 12 species of plants growing in Seropedica city, Rio de Janeiro, Brazil. We recovered six native hymenopteran parasitoid species: Doryctobracon areolatus (Szepligeti), Utetes (Bracanastrephae) anastrephae (Viereck), Opius bellus Gahan (Braconidae, Opiinae), Aganaspis pelleranoi (Brethes) (Figitidae, Eucoilinae), Trichopria anastrephae Lima (Diapriidae, Diapriinae) and an unidentified species of Pteromalidae. The most abundant parasitoid species was D. areolatus, representing 61.8% of all parasitoids. The parasitoid species recovered were well established in a wide diversity of fruit and Anastrepha fly species, including economically important pests such as A. fraterculus, A. obliqua and A. sororcula. The analysis of the relative abundance of the recovered parasitoids in different fruit species suggests, at least for the three encountered opiine parasitoids, that the host-parasitoid relationship was influenced by certain physical characteristics such as size and weight of the host fruit. Our results support the original proposal of M. Aluja and J. Sivinski (pers. comm.) that some native host plant species for the Anastrepha flies facilitate parasitoid multiplication. They deserve attention as natural enemy reservoirs and may be important to biological control strategies within fruit fly integrated management programs.

Re-test of Rhinocyllus conicus host specificity, and the prediction of ecological risk in biological control

Biological control is proposed as an ecological strategy to manage the threat of invasive plants, especially in natural areas. To pursue this strategy, we need to know that the host specificity criteria used to evaluate ecological risk with deliberate introduction of an exotic insect for biocontrol are sufficient to predict potential impact on native species. Host specificity is defined by adult feeding and oviposition preferences and larval development. One way to evaluate the criteria is to re-examine case histories where ecological effects are recorded, such as that of Rhinocyllus conicus Frölich. This flower head weevil, released in North America in 1968 to control exotic thistles like Musk thistle ( Carduus nutans L), is now reducing seed production by multiple native North American thistle species ( Cirsium spp.), and local population density of Platte thistle ( Cirsium canescens Nutt.). We hypothesized that host specificity of R. conicus has changed since pre-release testing, providing an explanation for the unexpected magnitude of the documented ecological effects. Instead, when we re-tested host specificity of weevils naturalized over 28 generations, we found that host specificity has not changed. Naturalized adults of R. conicus showed strong feeding and oviposition preference for Musk thistle over Platte thistle. In addition, larval development by these weevils was faster and more successful (to larger size) on Musk thistle than on Platte thistle. Thus, our results indicate that a change in host specificity cannot explain the unexpectedly large build-up of R. conicus and significant ecological effect on Platte thistle. We conclude that accurate prediction of the potential level of impact on native host plants in the field requires further ecological information in addition to host specificity.

Seasonal Distribution of the Leafhopper <I>Carneocephala floridana</I> (Homoptera: Cicadellidae) in North Florida Salt Marshes

Abstract The leafhopper Carneocephala floridana Ball is a common inhabitant of the salt marshes of north Florida. Although C. floridana is not usually economically important, increased agriculture and residential development in coastal areas may result in this insect becoming a more common pest species. Carneocephala floridana, like other members of this genus, is a likely vector of Pierce’s disease of grapes. This study documents the yearly distribution of C. floridana among its most common native host plants. Although C. floridana was present during every month of the year, it reached its highest densities during the spring and summer months on mixed herbaceous plant communities. It also exhibited smaller population peaks on some monocultures of smooth cordgrass, Spartina alterniflora Loiseleur-Deslongchamps, during the winter months, but these increases were most likely the result of immigration. Adult leafhoppers migrate from mixed herbaceous plant communities during the winter months, when these plan...

Registro de Plantas Hospedeiras (Cactaceae) e de Nova Forma de Disseminação de Diaspis echinocacti (Bouché) (Hemiptera: Diaspididae), Cochonilha-da-Palma-Forrageira, nos Estados de Pernambuco e Alagoas

Opuntia ficus-indica Mill. and Nopalea cochenillifera (L.) Lyons (Cactaceae) are alternative food sources for cattle in drought areas of the Northeastern Region of Brazil. Diaspis echinocacti (Bouche) is the unique pest of these Cactacea species and it was previously detected on the following native host plants: Cereus jamacaru DC., Melocactus sp., Opuntia dillenii Haw. and O. inamoena K. Schum. The new record of native hosts are Cereus gounellei (Weber) Luetzelb., C. squamosus Gerke. and the exotic C. hildemannianus K. Schum., from drought areas; Pereskia grandifolia Haw. and Epiphyllum oxypetalum Haw., native species from tropical forest used as ornamental plants. D. echinocacti has not infested O. monacantha Haw. in the field and in laboratory bioessays. The dissemination of the neonate scale insect transported on the body surface of the predators Chilocorus nigrita (Fabricius) and Zagreus bimaculosus (Mulsant) Coccinellidae: Chilocorinae) was registered for the first time.

Prepona pheridamas pheridamas (Cramer) e seus estágios imaturos (Lepidoptera, Nymphalidae, Charaxinae)

Data on immature stages and range extension of Prepona pheridamas (Cramer, 1777) are presented. The larva feed on Hirtella gracilipes (Hook. f.) (Chrysobalanaceae), the same natural hostplant for Agrias claudina godmani Fruhstorfer,1895 in the high Rio Arinos region, Mato Grosso State.

Flavonoid sequestration by the common blue butterfly Polyommatus icarus: quantitative intraspecific variation in relation to larval hostplant, sex and body size.

Common blue butterflies (Polyommatus icarus) sequester flavonoids from their larval food and store these pigments as part of their adult wing colouration. Insects were reared on 10 different diets to assess effects of host plants on variation in flavonoid sequestration in this moderately polyphagous butterfly. Rearing experiments revealed an unexpectedly large gradient in flavonoid richness, ranging from individuals with high flavonoid loads (reared on inflorescences of Medicago sativa, Trifolium repens, T. pratense) to butterflies which contained almost no such pigments (fed with foliage of M. sativa or Robinia pseudoacacia). Flavonoid sequestration was much more effective from natural hostplants than from experimentally offered diets which would not be accepted in the field. Female butterflies on average sequestered almost 60% more flavonoids than males. This sex difference was more pronounced on natural than on experimental diets. Flavonoid load was significantly and positively related to dry mass and forewing length as two important fitness correlates of butterflies. This correlation was particularly strong on experimental diets (i.e. under constraining conditions for development). On natural hostplants, in contrast, when butterflies generally were flavonoid-rich, no clear relationship between flavonoid load and size or mass emerged. Our analytical data are consistent with field results according to which females rich in UV-absorbing flavonoid wing pigments are more attractive to mate-searching males. In P. icarus, flavonoid richness might therefore increase visibility (by more effective sensory stimulation of the visual system), but could also confer information about the feeding history, and thus ontogenetically determined 'quality' of a potential mate.

Genetics, experience, and host-plant preference in Eurosta solidaginis: implications for host shifts and speciation.

Host-associated mating is crucial in maintaining the partial reproductive isolation between the host races of Eurosta solidaginis (Diptera: Tephritidae), a fly that forms galls on Solidago altissima and S. gigantea. (We refer to flies reared from S. gigantea as gigantea flies and those reared from S. altissima as altissima flies.) We measured the host preference of males and females of both host races, F1 hybrids between the host races, F2, and backcrosses to both host races. Male and female altissima flies and female gigantea flies had high host fidelity, whereas male gigantea flies had low host fidelity. This result suggests that there may be gene flow between the host races due to nonassortative mating that occurs when male gigantea mate with altissima females on S. altissima. This indicates assortative-mating mechanisms in addition to host-associated mating are required to produce the partial reproductive isolation between the host races that has been observed. Nongenetic factors had no influence on host preference. Larval conditioning did not influence host preference: reciprocal F1 hybrids reared in S. altissima and S. gigantea both preferred S. gigantea. Adult experience had no impact on host preference: females preferred their natal host plant regardless of which host they encountered first as an adult. The hypothesis that maternal effects influence preferences was rejected because male and female flies did not show a consistent preference for the host plant of their mother. We also found no evidence that preference was a sex-linked trait because F1 and backcrosses to the host races with different combinations of X chromosomes from the two host races preferred S. gigantea. Our results indicate that host preference is not determined by a large number of genes because preference of hybrids did not correspond to the proportion of the genome derived from each host race. The strength of the ovipuncture preference for S. gigantea by gigantea females, the females of both reciprocal F1 hybrids, the backcross to gigantea, and F2s indicates that preference is inherited nonadditively at a limited number of loci. The F1 female hybrids, however, had a weaker host preference for S. gigantea than the pure gigantea host race, indicating that there may be incomplete dominance or modifier loci. Males had different host preference patterns than females, with individual male gigantea and male F1 hybrids usually exhibiting preference exclusively for S. gigantea or S. altissima. One hypothesis explaining the difference in host preference between males and females is that the same gene influences both female and male host preference, but it is a sex-influenced gene. Thus, males carrying the gene for S. gigantea preference have an intermediate host preference, whereas females have a strong host preference to S. gigantea. In summary, we found that the host preference that produces host-associated mating is inherited nonadditively at a relatively small number of loci on autosomal genes. This mode of inheritance meets the assumptions of models of sympatric speciation, indicating that the host races could have evolved in sympatry.

Variation in hostplant preference and performance by the milfoil weevil, Euhrychiopsis lecontei Dietz, exposed to native and exotic watermilfoils.

Exotic plants often displace native plants and thus alter the availability of native hostplants for specialist herbivorous insects. The submersed aquatic weevil Euhrychiopsis lecontei Dietz is endemic to North America, but there are now source populations on the exotic Eurasian watermilfoil (Myriophyllum spicatum L.) as well as on the weevil's ancestral host, northern watermilfoil (Myriophyllum sibiricum Komarov). This provides an opportunity to examine a host range expansion in progress. To further define the host range of the weevil and to determine how population source and rearing plant influence host plant preference and performance, we conducted a series of preference and rearing experiments with weevils from two source populations reared on northern milfoil, on Eurasian milfoil, switched late in larval development from northern to Eurasian milfoil, and vice versa. We also included two rearing treatments with milfoils on which the weevil has not been documented: the native M. verticillatum L. and the exotic M. aquaticum Verd. Preference by weevils in the switched rearing treatments was similar to preferences exhibited by weevils reared solely on the second (later) milfoil species and an increase in preference for Eurasian milfoil was induced by adult exposure to Eurasian milfoil for 2weeks. In contrast, sizes and development times of weevils in the switched rearing treatments were similar to sizes and development times exhibited by weevils reared solely on the first (early) milfoil species. These results indicate that preference by the milfoil weevil is determined late in larval development or later and Hopkins' host selection principle is not supported. However, size and development time were most affected by hostplant quality during larval development when larvae must acquire the resources needed for pupation. Oviposition preference in the milfoil weevil was a population attribute, not a fixed individual attribute and there was no significant variation in preference among individuals reared on northern milfoil, but significant variation in preference was detected among weevils reared on Eurasian milfoil. Weevils oviposited on all four milfoil species and completed development on three of them, but did not develop beyond the larval stage on M. aquaticum. Weevils reared on Eurasian milfoil developed faster and reached larger adult sizes than weevils in any other rearing treatment. The smallest sizes and longest development times were for weevils reared on the natives, northern milfoil and M. verticillatum. The milfoil weevil oviposits on an array of milfoil species and is unable to distinguish an unsuitable host (M. aquaticum) within this genus. The influence of rearing plant and adult exposure to Eurasian milfoil on hostplant preference suggests that host range expansion to novel congeners may occur more rapidly than predicted by models which assume that genetic variation is required. Significant variation among individuals in hostplant preference suggests the potential for a host shift to a plant for which E. lecontei appears pre-adapted.

Effect of resistance variation in a natural plant host–pathogen metapopulation on disease dynamics

Existing theory suggests that increasing the diversity of resistance and virulence types in host–pathogen interactions will result in qualitative shifts in spatial and temporal dynamics, and greater among‐population asynchrony in disease dynamics and prevalence. Here, data are presented from a biologically realistic metapopulation model of gene‐for‐gene interactions that indicate that population level variation in resistance diversity will be negatively associated with disease prevalence (fraction of individuals infected). The model also predicts that disease incidence (presence/absence) will be positively related to total resistance diversity across the metapopulation, because high resistance diversity also selects for more virulent pathogens. These results are then contrasted with empirical data from a natural host–pathogen system. While the argument that high resistance diversity should generally lead to lower disease levels has been applied extensively in agricultural situations, the connection between genetic diversity, resistance and disease dynamics has never been demonstrated in natural systems. Here, through analysis of multiyear data on disease prevalence in the context of knowledge of resistance variation among host populations in a natural plant host–pathogen metapopulation, the first evidence is provided that observed levels of asynchrony in disease dynamics may indeed be related to resistance structure.

Psigida walkeri (Grote) e seus estágios imaturos (Lepidoptera, Saturniidae, Ceratocampinae)

The biology and immature stages of Psigida walkeri (Grote) are described for the first time. Development is rapid with only 35 days from egg to adult. The larva feed on Calliandra parviflora Benth. (Leguminosae-Mimosoideae), its natural host plant. Egg, larval instars, pupa and adults are illustrated in color.

Marginal range expansion in a host‐limited butterfly species Gonepteryx rhamni

Summary1. The British distribution of the butterfly Gonepteryx rhamni (L.) follows closely the range of its natural host plants, Rhamnus catharticus L. and Frangula alnus Miller, suggesting that it is one of the few British butterflies that has a host‐limited distribution. In North Wales, this species has its range margin, and it was recorded only occasionally in a 35‐km2 area prior to the 1980s. Frangula alnus bushes were planted in the area in about 1986, allowing the hypothesis that G. rhamni would expand its range following increased host plant availability to be tested.2. From 1996 to 1998, the distribution of the butterfly and its host plants, R. catharticus (native), Rhamnus alaternus L. (introduced), and F. alnus (introduced to the area but native to Britain), was mapped in the study area. It was found that the butterfly was more widespread than any of its host plants. Frangula alnus was the most widespread of the host plants, and received most eggs, suggesting that the carrying capacity of the habitat would have increased substantially following the planting of this species. Gonepteryx rhamni was able to complete its lifecycle on both introduced species in the study area.3. A mark–release–recapture study showed that adult G. rhamni moved an average of 512 m, and 50% of movements were further than 400 m; these values are underestimates. The relatively high mobility of this species suggests that it probably perceives host plants and nectar sources as resource patches (patchy population) in this fragmented landscape, and this population now represents a satellite population of the butterfly's main distribution in Britain.4. The results presented here confirm empirically the host‐limited distribution of G. rhamni, which expanded following the planting of extra host plants.

Effects of food plant and group size on predator defence: differences between two co‐occurring aposematic Lygaeinae bugs

Summary1. The role of food plant and aggregation on the defensive properties of two aposematic sympatrically occurring seed bugs, Tropidothorax leucopterus and Lygaeus equestris (Lygaeinae, Heteroptera), was investigated. Larvae reared on seeds either of their natural host plant Vincetoxicum hirundinaria (Asclepiadaceae) or of sunflower Helianthus annuus were subjected to predation by chicks.2. The two species differ in their dependency on the host for their defence. Lygaeus equestris was better defended on its natural host plant than on the alternative food, as indicated by fewer attacks, lower mortality, and predator avoidance after experience. No such effect of food plant could be found for T. leucopterus, suggesting the existence of alternative defences in this species.3. The number of attacks was lower when host plant‐fed larvae of both species were presented in groups.4. The discussion concerns how major components of an aposematic syndrome, such as host plant chemistry, insect colouration, and aggregation, are integrated with other life‐history traits to form alternative lifestyles in L. equestris and T. leucopterus.

The making of a pest: recruitment of Meligethes aeneus onto oilseed Brassicas

AbstractPopulations of the rapeseed pollen beetle Meligethes aeneus F. (Col., Nitidulidae) from areas with 0–16 years of history of intensive rapeseed growing were compared for key ecological characters. During the first 16 years of rapeseed cultivation the reproductive success of M. aeneus increased 200–300% over that of the beetles living on the natural host plants, cruciferous weeds. The increase was linear over time and statistically highly significant, and it did not appear to be related to food quality or to the size of the beetles. During the same period the tolerance to intraspecific competition decreased, possibly due to the relative absence of such competition on the new crop. Furthermore, the optimum population density for M. aeneus to maximize the size of its next generation on summer turnip rape was determined to be 0.5–1.0 beetles/plant, which is slightly below the economic threshold for chemical control (1 beetle/plant). Therefore the practical protection of the rapeseed yield also ensures the highest possible pest population size for the next year. These mechanisms may in part explain the particular noxiousness of the species as a pest all over Europe. In general these data show that after the introduction of a new crop plant into a region, significant changes during the recruitment process in a pestiferous insect may take place, contributing to the future pest status of the insect. It is suggested that such genetic and ecological changes in insects may be a more common mechanism than previously thought in initiating and sustaining pest outbreaks, and that conventional pest management methods may enhance that effect.

Novel, Non-Solanaceous Hostplant Record for <I>Manduca sexta</I> (Lepidoptera: Sphingidae) in the Southwestern United States

Abstract Field observations in the Tucson, AZ, basin reveal that Manduca sexta (L.) has been incorrectly described in the past as a specialist herbivore that oviposits and feeds exclusively on plants in the family Solanaceae. We present evidence that previously unreported, non–solanaceous hostplants are routinely used by M. sexta females for oviposition. These plants permit successful larval development, through to emergence of the next generation of adults. The novel hostplants, 2 species of the genus Proboscidea, belong to the Martyniaceae, a family taxonomically distant from the Solanaceae. Our observations on oviposition and larval feeding were conducted during 2 consecutive field seasons. During the 2nd field season, we counted M. sexta eggs on native hostplants, both solanaceous (Datura wrightii, Regel) and non–solanaceous (2 Proboscidea species), and found higher abundance of eggs on the Proboscidea spp., in approximately a 3:1 ratio. Our results challenge the commonly held view that M. sexta is a ...

Foraging in nature by larvae of Manduca sexta—influenced by an endogenous oscillation

Foraging by larvae of the moth Manduca sexta was studied in the field on the native host plant Datura wrightii. Continuous observation of individuals revealed that larvae moved very little, but fed for approximately one third of the time, independent of temperature or photoperiod, although the larger ones fed for the longest times. They were indiscriminate with respect to the part of plant fed upon, and analysis of feeding bouts and interbouts indicated that the pattern of feeding was not strongly influenced by direct nutritional factors. Attacks by parasitoids had a significant impact on feeding behavior. All individuals showed strong regularity in the times when feeding was initiated, and analyses demonstrated that feeding was initiated at times corresponding to fitted oscillation periods of approximately 4 min. Feeds were not initiated on every peak, but at times corresponding to the primary period, or harmonics of it. The period was not influenced by temperature, was different for all individuals, and was asynchronous among individuals. We conclude that an endogenous neural oscillation underlies the rhythm, and strongly influences the overall pattern of foraging. We discuss the oscillation in terms of its possible ecological significance, particularly the need for vigilance.

Induced responses in Nicotiana attenuata affect behavior and growth of the specialist herbivore Manduca sexta.

Many plants employ induced responses against generalist herbivores. Specialist herbivores, however, may employ several mechanisms to overcome the negative effects of induced plant defenses. Here we test how the behavior and development of specialist Manduca sexta larvae are affected by induced responses in their natural host plant Nicotiana attenuata. On a spatial scale relevant to both the plant and the herbivore, we first determined how methyl jasmonate (MeJA)-induced responses, such as increased nicotine production, affect the tendency of larvae to leave induced plants. When larvae were allowed to move between two plants planted in one pot, they left an MeJA-treated plant faster than a control plant. When both plants in the pot were MeJA-treated, the larvae developed more slowly than when both plants were uninduced, or when the larvae had the opportunity to move to an uninduced neighbor. The sooner larvae moved from an MeJA-treated plant to an untreated neighbor, the larger the body mass they attained. This demonstrates that M. sexta larvae can compensate behaviorally for the deleterious effects of induced plant responses. These effects were observed in plants grown under both low and high N supply rates, though the effects were more pronounced under high N. To examine the consequences of the timing and the direction of the host plant switching behavior for larval development, neonate larvae were fed leaves excised from induced and uninduced plants. Larvae confined to MeJA-treated leaves had higher mortality rates and grew slower than larvae fed only control leaves. This demonstrates that MeJA-induced responses decrease growth and development of specialist herbivores that do not have the behavioral option of moving to an uninduced plant. The sooner the larvae were switched to MeJA-treated leaves, the slower their development compared to larvae fed only uninduced leaves. In contrast, the sooner larvae fed MeJA-treated leaves were switched to control leaves, the faster they developed. Again the effects of MeJA treatment were stronger in plants grown under high N supply. We propose that induced plants growing in close competition with an uninduced conspecific may offset the fitness costs of these induced responses and perhaps obtain a fitness benefit by motivating herbivores to move to their neighboring competitors.

MATERNAL EFFECTS MEDIATE HOST EXPANSION IN ASEED-FEEDING BEETLE

Texas ebony (Chloroleucon ebano) has recently been introduced as an ornamental tree in the Phoenix metropolitan area of Arizona (USA). It has since been colonized by the seed beetle Stator limbatus (Coleoptera: Bruchidae), and seeds of Texas ebony support the development of beetles to reproductive maturity in nature and in the laboratory. Egg size affects the larval survivorship of beetles on seeds of Texas ebony. Females of S. limbatus exhibit egg-size plasticity in response to native host plants; they lay small eggs if they encounter seeds of catclaw acacia (Acacia greggii) and lay large eggs if they encounter seeds of the blue paloverde (Cercidium floridum). We tested the hypothesis that oviposition experiences of female S. limbatus on native plants affects the ability of their larvae to develop on seeds of the nonnative Texas ebony. We demonstrate that females that encounter the native C. floridum while they are maturing their eggs produce progeny that have survivorship 10 times higher on seeds of the introduced Texas ebony than that of progeny produced by females that do not encounter C. floridum during egg maturation. However, this result cannot be explained entirely by egg-size plasticity; survivorship of larvae differed among treatments even in the range of egg sizes that overlapped between treatments. These results thus indicate that females exhibit plasticity in egg size and egg composition, and that this plasticity facilitates the expansion of S. limbatus onto seeds of a nonnative plant. Our study thus demonstrates that maternal effects can influence species interactions within communities, and that we should consider these maternal effects when predicting the ecological and evolutionary consequences of changing species distributions.

Brome mosaic virus RNA replication proteins 1a and 2a colocalize and 1a independently localizes on the yeast endoplasmic reticulum.

The universal membrane association of positive-strand RNA virus RNA replication complexes is implicated in their function, but the intracellular membranes used vary among viruses. Brome mosaic virus (BMV) encodes two mutually interacting RNA replication proteins: 1a, which contains RNA capping and helicase-like domains, and the polymerase-like 2a protein. In cells from the natural plant hosts of BMV, 1a and 2a colocalize on the endoplasmic reticulum (ER). 1a and 2a also direct BMV RNA replication and subgenomic mRNA synthesis in the yeast Saccharomyces cerevisiae, but whether the distribution of 1a, 2a, and active replication complexes in yeast duplicates that in plant cells has not been determined. For yeast expressing 1a and 2a and replicating BMV genomic RNA3, we used double-label confocal immunofluorescence to define the localization of 1a, 2a, and viral RNA and to explore the determinants of replication complex targeting. As in plant cells, 1a and 2a colocalized on and were retained on the yeast ER, with no detectable accumulation in the Golgi apparatus. 1a and 2a were distributed over most of the ER surface, with strongest accumulation on the perinuclear ER. In vivo labeling with bromo-UTP showed that the sites of 1a and 2a accumulation were the sites of nascent viral RNA synthesis. In situ hybridization showed that completed viral RNA products accumulated predominantly in the immediate vicinity of replication complexes but that some, possibly more mature cells also accumulated substantial viral RNA in the surrounding cytoplasm distal to replication complexes. Additionally, we find that 1a localizes to the ER when expressed in the absence of other viral factors. These results show that BMV RNA replication in yeast duplicates the normal localization of replication complexes, reveal the intracellular distribution of RNA replication products, and show that 1a is at least partly responsible for the ER localization and retention of the RNA replication complex.

Biologia de Tuta absoluta (Meyrick, 1917) em dieta artificial

O presente trabalho teve por objetivo desenvolver uma dieta artificial para a criação da traça-do-tomateiro (Tuta absoluta) sem a dependência do hospedeiro natural (tomateiro). A dieta empregada tem como fontes protéicas germe de trigo, levedura, caseína e farelo de soja, além do feijão, que foi a variável do trabalho. A dieta mais adequada para a criação da traça-do-tomateiro foi o hospedeiro natural, no caso, as folhas de tomateiro ‘Santa Clara’ e, dentre os meios artificiais, o que se mostrou mais promissor foi aquele com feijão Branco acrescido de pó de folha de tomateiro. Este pó de folhas apresentou um efeito fagoestimulante, diminuindo a mortalidade inicial e aumentando a viabilidade total do inseto no meio artificial. O número de ínstares foi constante e igual a 4, tanto nas dietas artificiais como na dieta natural, indicando a adequação nutricional dos meios artificiais.

Innate attraction supplants experience during host plant selection in an obligate plant-ant

In order to assess the relative contributions of innate attraction and environmentally-induced preference to nest plant selection by the obligate plant-ant Tetraponera aethiops, we submitted both mature and callow workers to paired choice tests using the leaves of four plant species, including their natural host plant Barteria fistulosa. Mature workers taken from nature as well as mature workers after 25 days of laboratory breeding (with or without contact with B. fifstulosa leaves) always showed a great preference for shelters made with the leaves of B. fistulosa. Similar results were obtained with callow workers isolated from any plant material during the first 25 days of imaginal (=adult) life or during pre-imaginal development. But those reared in contact with test-plant leaves for the same two periods showed significantly less preference for B. fistulosa than did the controls. As a result, experience gained during the larval and nymphal stages as well as during the first part of adult life (i.e. pre-imaginal as well as early learning) was demonstrated in T. aethiops, but in this situation of species-specific interaction it reinforces innate attraction as both larvae and adults live in contact with B. fistulosa in nature. These results are discussed in comparison with previous data collected on arboreal ants not specifically paired with a plant, for which an environmentally-induced preference can supplant innate attraction.