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Ambrosia beetles from the tribe Xyleborini are part of nearly all forest ecosystems. Because of their small size, haplodiploid mating structure, and protected lives inside the sapwood of woody plants, they have a unique ability to expand into new regions via inadvertent human transport. A small number of invasive xyleborines cause significant damage to forests, lumber concerns, and agricultural systems. Most ambrosia pests damage or kill trees by the accumulation of beetle attacks, one is known to cause tree death through the introduction of pathogenic fungus into susceptible Lauraceae trees. The relationships between ambrosia fungi and their beetle vectors range from mutualistic symbiosis to facultative association, but most remain unstudied. Unresolved taxonomies, convergent morphologies, and the difficulty of sampling ambrosia fungi over their entire global ranges make comprehensive surveys of ambrosia fungi difficult to achieve. Ambrosia fungi from Europe and North America are moderately well documented, however, we have yet to sufficiently document those from Africa, Asia, Australia, and South America. Worldwide cooperation to improve and standardize scientific study of the ambrosia symbioses is needed to better understand these impactful organisms.

Resumen El objetivo de este estudio fue determinar la fluctuación poblacional de Premnobius cavipennis y el efecto de la altura de trampa en plantaciones de balso (Ochroma pyramidale) en las localidades de El Vergel, El Empalme y Guapara en Ecuador. Se usaron trampas de intercepción de vuelo con alcohol como atrayente, colocadas a uno, cuatro y ocho metros de alto. La recolecta y evaluación se realizó cada semana durante un año por localidad. Las poblaciones de P. cavipennis, fluctuaron durante el año, con máximas poblacionales en el periodo lluvioso en las tres localidades. En El Vergel se encontró mayor abundancia con 2.382 individuos, máxima poblacional en diciembre. En El Empalme se capturaron 1.263 individuos, con alzas poblacionales en enero y abril. En Guapara se registraron 525 individuos, con un pico poblacional en marzo. Los individuos de P. cavipennis se capturaron en las tres alturas de las trampas en las tres localidades. Hubo diferencias altamente significativas entre las alturas con un mayor efecto de altura de trampa en la captura de individuos a un metro, comportamiento que fue igual en las tres localidades. Abstract This study aimed to determine the population fluctuation of Premnobius cavipennisand the effect of the trap height on balsa plantations (Ochroma pyramidale). The research was in El Vergel, El Empalme, and Guapara, three localities of Ecuador. There were used flight-interception traps with alcohol as an attractant, placed at one, four, and eight meters high. The collection and evaluation were carried out every week, for one year by locality. Premnobius cavipennis showed a population fluctuation throughout the year, with population peaks in months of the rainy season in the three locations. In El Vergel, the greatest abundance of P. cavipennis was found with 2,382 individuals, showing a population maximum in December. In El Empalme 1,263 individuals were captured, with population increases in January and April. In Guapara 525 individuals were registered, showing a population increase in March. There were captured individuals of P. cavipennis in the three heights of the traps in the three locations. There were highly significant differences between the heights, with a greater effect on the capture at one meter in the three locations of individuals at one meter, behavior that was the same in the three locations.

Coptoborus ochromactonus Smith and Cognato is a recently described xyleborine ambrosia beetle pest associated with balsa, Ochroma pyramidale (Cav. Ex Lam.) Urb., in Ecuador. This pest has caused significant loss of cultivated balsa in Ecuador, but little is known of its biology and ecology. Based on examination of multiple gallery systems, this study describes the gallery pattern and life cycle of C. ochromactonus and confirms the generic identity of the symbiotic fungus. Females initiated attack, excavating a gallery perpendicular to the bole. The primary tunnel branched into a secondary tunnel at a mean 3.13 mm. This first secondary tunnel was excavated in a horizontal plane between the phloem and xylem for a mean 18.0 mm. Along its length, two tertiary tunnels were constructed on each side, measuring a mean 26.0 and 20.0 mm, respectively. Conidiophores and conidia of an unidentified Fusarium sp. grew on the tunnel walls and were fed upon by the beetle and her progeny. Coptoborus ochromactonus exhibits sexual dimorphism. The female is 2.6 mm long and possesses a round pronotum, whereas the male is 2.2 mm long and has a quadrate pronotum. The developmental stages last a mean 6, 14, 6, 4 and 30 d for egg, larva, pupa, teneral adult, and adult, respectively, when reared at 25°C. Three larval instars were present, with mean head capsule widths of 0.23, 0.31, and 0.42 mm, respectively. In general, the life cycle of C. ochromactonus is similar to those described for other xyleborine ambrosia beetle species.