Resumen Los productos o substancias volátiles de plantas median las interacciones entre los organismos de diferentes niveles tróficos, incluidos los insectos fitófagos. Estas interacciones se han citado en un contexto químico-ecológico para especies de Coleoptera Melolonthidae. Sin embargo, no hay informes previos sobre estas interacciones entre las especies de Melolonthidae distribuidas en México y sus plantas hospederas. Por ello, se registró la interacción entre adultos de Macrodactylus nigripes Bates (Coleoptera:Melolonthidae) y el arbusto de azumiate (Baccharis salicifolia Ruíz and Pav.) Pers. (Asteraceae) y se extrajeron e identificaron los compuestos volátiles de las hojas que podrían estar involucrados en la atracción de estos insectos. Se describió la secuencia de patrones de comportamiento que conforman esta interacción. Se observó que las hembras de M. nigripes emergen del suelo y se desplazan en vuelo hacia las hojas de los arbustos de azumiate. Cada hembra se posiciona en la hoja y colocan sus mandíbulas en el margen de éstas y comienzan a moverlas de derecha a izquierda para obtener pequeños fragmentos de hojas e ingerirlos. Asimismo, las hembras muestran un patrón de comportamiento de ‘llamado sexual’. Enseguida, los machos emergen del suelo y repiten el comportamiento de las hembras, acercándose a ellas para la cópula. Se generó un listado de los compuestos volátiles de las hojas de azumiate mediante microextracción en fase sólida (SPME, por sus siglas en inglés) y cromatografía de gases acoplada a espectrometría de masas (CG-EM), donde los compuestos más abundantes fueron a-pineno, trimetilindan y ciclohexilbenceno. Estos compuestos se han reportado anteriormente en otras especies de plantas, incluidas algunas especies consideradas como plantas hospederas para integrantes de Melolonthidae.

Abstract Plant products or substances medíate interactions among organisms from different trophic levels, including phytophagous insects. These interactions have been cited in a chemical-ecology context for species of Coleoptera Melolonthidae. However, there are no previous reports of these interactions among melolonthid beetles species distributed in Mexico and host plants. For the above, the interaction between adults of ‘rose chafer’ Macrodactylus nigripes Bates (Coleoptera: Melolonthidae) and ‘seep willow’ shrub Baccharis salicifolia (Ruíz and Pav.) Pers. (Asteraceae) was recorded and the leaves volatiles of seep willow that might be involved in the attraction of these insects were extracted and identified. The sequence of behavior patterns that conforms this interaction was described. Females of M. nigripes emerge from the soil and flight to the leaves of seep willow shrubs. Each female settled on leaf and they place their mandibles on the leaf margin and start moving them from right to left to obtain small leaf fragments to ingest. In addition, females exhibit a similar ‘calling’ behavior as well as the others species. Following the females, males emerge from the soil and repeat the females’ behavior, approaching them for mating. A list of the leaves volatiles of seep willow was generated by solid phase microextraction (SPME) and coupled gas chromatography - mass spectrometry (GC-MS), where the most abundant chemicals were a-pinene, trimethylindan and cyclohexylbenzene. These compounds have been previously reported in other plant species, including some species considered as host plants for Melolonthidae.

The external morphology of sensilla on the antennae of males and females of Phyllophaga ravida Blanchard is described using scanning electron microscopy. Sexual dimorphism in body and antennal dimensions and in antennal receptor types was found. The female's body is slightly larger than the male's, although male antennal lamellae are longer than in females. Sixteen types of sensilla were identified on the proximal and distal surfaces of lamellae from both sexes, most of them in males: three types of placodea sensilla, four types of auricilica sensilla, five types of basiconica sensilla, and four types of coeloconica sensilla. Also, two types of mechanoreceptor sensilla were present on the lamellae periphery. Furthermore, males had larger placodea, auricilica and some types of basiconica sensilla.