The behaviour of 9 stored product beetles at pitfall trap arenas and their capture in millet

Abstract

Pitfall trap capture for Sitophilus oryzae (L.), S. zeamais (Motschulsky), S. granarius (L.), Tribolium confusum (Duval), T. castaneum (Herbst); Oryzaephilus surinamensis (L.), Cryptolestes pusillus (Schonherr), Rhyzopertha dominica (Fabr.), and Prostephanus truncatus (Horn) in millet was assessed by visual and time‐lapse video recordings. The behaviour of different beetle species in arenas containing millet was monitored over 24 h and the frequency of encounters with the trap rim resulting in capture recorded. The capture efficiency of four types of pitfall traps (i.e. polystyrene, polythene, glass and tin‐plated steel can) with rims exposed or submerged below the millet surface level were compared. Capture was related to beetle size, locomotory rate, and beetle behaviour at the trap rim as well as trap design and placement. The lighter and smaller species were least captured. Glass jars were more effective than plastic and metal containers. Traps placed with their rims submerged below the grain surface level were more efficient than those with rims exposed. Capture rate was unrelated to trap size. The frequency of encounters with trap rims was not correlated with capture rate. Three types of avoidance behaviours at the trap rims i.e. probing, skirting and spontaneous retreat, were related to capture rate, spontaneous retreat being the most effective escape mechanism and probing least.

Pitfall Trapping in Ecological Studies

“…Species-specific responses to trap material are common (Luff 1975, ObengOfori 1993. Glass is normally found to be the most effective material in terms of numbers of individuals captured, and is almost always superior to metals (Luff 1975, Obeng-Ofori 1993. The superiority of glass over other materials is particularly important if live catches are required.…”

“…It has been suggested that the trap rim should be placed 1-7 mm below the level of the substrate surface (Good & Giller 1991, Obeng-Ofori 1993. However, this is normally awkward, and for large numbers of traps may be impractical.…”

“…These behavioral differences will influence rates of capture independent of the activity and density of different species (e.g. Den Boer 1981, Halsall & Wratten 1988, Morrill et al 1990, Obeng-Ofori 1993, Topping 1993, Mommertz et al 1996. Nonetheless, this concept is valuable in the interpretation of pitfall trap catches.…”

“…The technique has also been used to obtain information on the structure of invertebrate communities (Hammond 1990, Jarosík 1992, habitat associations (Honêk 1988, Hanski & Niemelä 1990, activity patterns (Ericson 1978, Den Boer 1981, spatial distribution (Niemelä 1990), relative abundances (Desender & Maelfait 1986a, Mommertz et al 1996, total population estimates (Gist & Crossley 1973, Mommertz et al 1996, and distribution ranges (Barber 1931, Giblin-Davis et al 1994. Pitfall trapping also plays a role in some pest monitoring programs (Kharboutli & Mack 1993, Obeng-Ofori 1993, Rieske & Raffa 1993, Simmons et al 1998. For the last three-quarters of a century pitfall traps have proved to be one of the most versatile, useful, and widely used invertebrate sampling techniques.…”

Direct assessment of nutrient resources in free-range and scavenging systems

“…This is an estimate of the probable feed materials available on the range and is carried out by the use of pitfall traps, transect mapping and quadrants. Pitfall traps are used to estimate the quantity of crawling insects and other metazoans which are available in a reference area (Obeng-Ofori, 1994). An area 1 m 2 is used for each estimation.…”