Dispersão de Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae) em trigo armazenado, sob condições artificiais

Abstract

-Ability to disperse is fundamental for a successful natural enemy in a stored grain environment. The objective of the present work was to assess whether the mite Acarophenax lacunatus (Cross & Krantz) disperses in a grain mass to locate its host Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae). The experiment was based on the release of physogastric females of A. lacunatus on the surface of glass containers containing Petri dishes with 20 adults of R. dominica at different depths (4, 8, 12, 16 and 20 cm). The Petri dishes were covered with voil to prevent insect escape. Dispersion of the progeny of these physogastric females was assessed 10, 20 and 30 days after the beginning of the experiment. The mites were able to disperse and they were observed at every depth and at every period of assessment. Nonetheless, the number of A. lacunatus decreased with the increasing depth, with highest values observed at the lowest depths after 20 and 30 days of storage. It is possible that evaluations conducted in periods longer than 30 days of the parasite release could demonstrate an increase in parasitism at higher depths. The results indicated that A. lacunatus actively disperse for up to 20 cm on its own, without the assistance of its host for phoresy.

Walking stability of Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae)

“…In an attempt to simulate the physical conditions of a storage structure are used glassware and recipients that facilitate handling in the laboratory, observing (at the time of its selection) conditions such as material used (glass bottle/jar, Petri-dish, plastic pot/recipient, raffia bag), size of the recipient/arena (height, width, length, diameter), information which can be confirmed in several studies (Aguiar et al, , 2010Beckel et al, 2005;Belchol and Teixeira, 2007;Fontes and Arthur, 1994;Gonçalves et al, 2006Gonçalves et al, , 2007Moino Junior and Alves, 1997;Oliveira et al, 2003Oliveira et al, , 2006Pereira et al, 2003;Silva et al, 2003).…”

“…Rhyzopertha dominica and T. castaneum have been studied under different climatic conditions, with variations as needed (Aguiar et al, , 2010Beckel et al, 2005;Fontes and Arthur, 1994;Gonçalves et al, 2006Gonçalves et al, , 2007Moino Junior and Alves, 1997;Oliveira et al, 2003Oliveira et al, , 2006Silva et al, 2003), and care with the method of simulating the physical structure of the storage unit should be taken into consideration so that the results may express the condition closest to the actual condition (Beckel et al, 2005;Gonçalves et al, 2006Gonçalves et al, , 2007Ortiz et al, 2012;Pacheco et al, 2009).…”

“…Measures taken to guarantee that these Coleoptera are able to move are those obtained from experimental experience with the insect, for example, always maintaining a thin layer of grain or bran to facilitate its displacement, or covering the surface of the arena with paper or cloth. However, existing studies that relate the movement of insects in the stored product only consider the fact that they are already in contact with the grain mass in the arena (Beckel et al, 2005;Oliveira et al, 2003Oliveira et al, , 2006. There are no studies that discuss the behavior of adults on flat and smooth surfaces, to which they may be submitted and required to walk or move in laboratory studies.…”