Tilting chains of negative curves on rational surfaces

We introduce the notion of exact tilting objects, which are partial tilting objects $T$ inducing an equivalence between the abelian category generated by $T$ and the category of modules over the endomorphism algebra of $T$. Given a chain of sufficiently negative rational curves on a rational surface, we construct an exceptional sequence whose universal extension is an exact tilting object. For a chain of (-2)-curves, we obtain an equivalence with modules over a well known algebra.Comment: 13 page

Importation and Preliminary Evaluation of the Stem Boring Moth Buakea kaeuae as a Potential Biological Control Agent of Invasive Guineagrass, Megathyrsus maximus

Abstract. Guineagrass, Megathyrsus maximus (Jacq.) B.K.Simon & S.W.L.Jacobs, is an African grass that is invasive in Florida, Hawaii, southern Texas, and northeastern Mexico. Buakea kaeuae Moyal et al., a stem-boring African moth found only on M. maximus, was imported from Kenya and evaluated for its ability to feed and develop on Guineagrass naturalized in southern Texas. Neither larvae nor adults developed or reproduced on Texas Guineagrass. Resumen. El zacate Guinea (Megathyrsus maximus (Jacq.) B.K.Simon & S.W.L.Jacobs), originario de África, es considerado invasivo en Florida, Hawaii, sur de Texas, y noreste de México. Buakea kaeuae Moyal et al. es una palomilla especifica de M. maximus que ataca a los tallos de esta maleza. Esta palomilla fue importada de Kenia y ha sido evaluada por su habilidad para alimentarse y desarrollar su ciclo biológico solo en plantas de zacate guinea, naturalizadas en el sur de Texas. Ni las larvas ni los adultos de B. kaeuae, se desarrollan y reproducen en especies de zacate Guinea de Texas

Molecular phylogenetics, systematics and host-plant associations of the <em>Bruchidius</em> albosparsus (Fåhraeus) species group (Coleoptera, Chrysomelidae, Bruchinae) with the description of four new species.

International audienceBruchidius Schilsky is a large paraphyletic genus of seed beetles (Coleoptera: Chrysomelidae: Bruchinae) which consists of multiple lineages that are usually associated with narrow sets of host-plants. In this study we focus on a group that mostly develops on wattle trees (acacias) belonging to the genus Vachellia Wight & Arn. This group originally included nine species and was designated as the Bruchidius centromaculatus (Allard) species group, but recent phylogenetic analyses revealed that these species belong to a much wider group of species with similar morphologies. For reasons of anteriority we call this enlarged group Bruchidius albosparsus (Fåhraeus). Here we review the morphology of species in this group and provide new diagnoses and ecological data for 10 species. The following combinations and synonymies are proposed: Bruchidius tanaensis (Pic, 1921) (= Bruchus tanaensis Pic, 1921) comb. nov. and Bruchidius albosparsus (Fåhraeus, 1839) (= Bruchus spadiceus Fåhraeus, 1839) syn. nov. Four new species are also described: B. eminingensis sp. nov., B. gerrardiicola sp. nov., B. glomeratus sp. nov. and B. haladai sp. nov. Finally we carried out molecular phylogenetic analyses on a multi-marker dataset of 59 specimens and 35 species, including 14 species from the group. The resulting trees allow us to confirm the monophyly of the group of interest and provide a more detailed picture of their evolutionary relationships

Cannibalism and intraguild predation involved in the intra- and inter-specific interactions of the invasive fall armyworm, Spodoptera frugiperda, and lepidopteran maize stemborers

Cannibalism and intraguild predation can play important roles in determining spread and survival or death of organisms which share the same resource. However, the relationship between cannibalism and intraguild predation, and the costs and benefits of such behaviours, is difficult to establish within insect communities, and little is known about how such behaviours are affected by invasive species. The present study was aimed at assessing the interactions between larvae of fall armyworm (Spodoptera frugiperda) and maize stemborers (native to Africa, Busseola fusca, and Sesamia calamistis and native to India, Chilo partellus) in relation to cannibalism and intraguild predation when they utilize the same resource. Experiments involving treatments with either single species of S. frugiperda or any of the stemborers or pairwise species combinations with S. frugiperda were conducted under laboratory conditions. The experimental insect larvae were reared on maize leaves and monitored until the last developmental stage where cannibalism and/or intraguild predation, larval survival, and relative growth rate were recorded. Results of the intraspecific interaction indicated that S. frugiperda exhibited cannibalism to a larger degree than the stemborers species, especially at the late instars. The higher cannibalism trait in S. frugiperda turned, however, to competitive advantage as it led to a higher degree of intraguild predation when they cohabit with stemborer species and allowed FAW to gain a greater relative growth rate. Overall, interactions with FAW are detrimental for stemborer species and may be an important factor to explain the invasive success of S. frugiperda. Such knowledge is essential to understand the mechanisms behind ecological interactions between pests with overlapping niches in the field and in designing successful integrated pest management strategies

FIGURES 5 – 8 in Molecular phylogenetics, systematics and host-plant associations of the Bruchidius albosparsus (Fåhraeus) species group (Coleoptera, Chrysomelidae, Bruchinae) with the description of four new species

FIGURES 5 – 8. Bruchidius elnairensis (male): 5 — median lobe (ventral view); 6 — lateral lobes (ventral view); Bruchidius eminingensis (male): 7 — median lobe (ventral view); 8 — lateral lobes (ventral view)

Influence of feeding-damaged plants on the oviposition responses within a community of female moths

Competitive or facilitative interactions characterise phytophagous insect communities that utilise the same resources. These interactions are often mediated by the host plant. Plant mediation influences the oviposition choices that a community of insects, sharing the same host plant make. In this context, the oviposition choices of females within a community of lepidopteran cereal stemborers namely Busseola fusca, Sesamia calamistis and Chilo partellus were studied in plant choice-experiments under laboratory and field conditions. Gravid females of each species were presented with a choice between maize plants infested by conspecific or heterospecific larvae and uninfested maize plants. The number of eggs and egg batches laid on plants were used to quantify oviposition. Results showed that none of the three stemborer species avoided oviposition on infested maize plants. In some cases a significant preference for infested maize plants were observed. Similarly, data from field trials under natural stemborer infestation, with B. fusca as the only species, showed that the wild ovipositing moths were not avoiding infested plants. Host plant mediation may influence the incidence of multi-species infestations by stemborer species often found in the field. The potential roles of herbivore-induced and egg-deposited-induced plant volatiles in this mechanism are discusse

Cannibalism and intraguild predation involved in the intra- and inter-specific interactions of the invasive fall armyworm, Spodoptera frugiperda, and lepidopteran maize stemborers

Cannibalism and intraguild predation can play important roles in determining spread and survival or death of organisms which share the same resource. However, the relationship between cannibalism and intraguild predation, and the costs and benefits of such behaviours, is difficult to establish within insect communities, and little is known about how such behaviours are affected by invasive species. The present study was aimed at assessing the interactions between larvae of fall armyworm (Spodoptera frugiperda) and maize stemborers (native to Africa, Busseola fusca, and Sesamia calamistis and native to India, Chilo partellus) in relation to cannibalism and intraguild predation when they utilize the same resource. Experiments involving treatments with either single species of S. frugiperda or any of the stemborers or pairwise species combinations with S. frugiperda were conducted under laboratory conditions. The experimental insect larvae were reared on maize leaves and monitored until the last developmental stage where cannibalism and/or intraguild predation, larval survival, and relative growth rate were recorded. Results of the intraspecific interaction indicated that S. frugiperda exhibited cannibalism to a larger degree than the stemborers species, especially at the late instars. The higher cannibalism trait in S. frugiperda turned, however, to competitive advantage as it led to a higher degree of intraguild predation when they cohabit with stemborer species and allowed FAW to gain a greater relative growth rate. Overall, interactions with FAW are detrimental for stemborer species and may be an important factor to explain the invasive success of S. frugiperda. Such knowledge is essential to understand the mechanisms behind ecological interactions between pests with overlapping niches in the field and in designing successful integrated pest management strategies

Influence of Si in maize plants in Kenyan populations of Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), native to the Americas, was confirmed in West and Central Africa in 2016 and reported in almost all countries of sub-Saharan Africa in 2017, becoming thereafter one of the major constraints on the production of maize, the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Both FAW strains, namely rice and corn strains, have been found to be present in Kenya. The present study tested the influence of Si on larval survival and relative growth rate according to the FAW strain, using potted maize plants treated with 10 and 20 g of Si. The results showed that plants treated with Si disturbed the larval growth of FAW larvae only from the corn strain but not from the rice strain. Overall, the corn strain performed better on maize as compared to the rice strain regardless of Si treatment, explaining why it has become the most abundant strain in Africa

Influence of Si in maize plants in Kenyan populations of Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), native to the Americas, was confirmed in West and Central Africa in 2016 and reported in almost all countries of sub-Saharan Africa in 2017, becoming thereafter one of the major constraints on the production of maize, the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Both FAW strains, namely rice and corn strains, have been found to be present in Kenya. The present study tested the influence of Si on larval survival and relative growth rate according to the FAW strain, using potted maize plants treated with 10 and 20 g of Si. The results showed that plants treated with Si disturbed the larval growth of FAW larvae only from the corn strain but not from the rice strain. Overall, the corn strain performed better on maize as compared to the rice strain regardless of Si treatment, explaining why it has become the most abundant strain in Africa