Schistocerca gregaria is one of the most well-studied organisms in terms of the effect of rearing density in laboratory settings. When solitarious nymphs are crowded, they begin to exhibit gregarious behavior within four hours (Roessingh and Simpson 1994) . Among all possible sensory cues, tactile stimuli have the strongest effect in shifting phase (Roessingh et al. 1998) . Gregarious behavior can be induced by stimulating mechanosensory receptors located on the outer surface of hind femur (Simpson et al. 2001) . When crowing persists, the chemical composition of nymphal pheromone changes, which keeps the group cohesive (Obeng-Ofori et al. 1993, Obeng-Ofori et al. 1994) . Upon crowing, black pigmentation develops, which may a result of [His7]-corazonin expression (Tawfik et al. 1999) . Background color also changes from green to yellow within an instar and a full color change is visible after molting. Morphometric ratios may take several generations to change from solitarious to gregarious ratios, but it is shown to be affected by [His7]-corazonin (Hoste et al. 2002, Maeno et al. 2004) . The rate of sexual maturation increases upon crowding (Norris 1952) . The phase status is transmitted across generations. Ovipositing females can determine the phase status of offspring based on the density at mating and oviposition by producing a gregarizing factor probably from accessory glands via egg foam (McCaffery et al. 1998) . Phase expressions are reversible and not always coupled. Thus, it is possible to observe solitarious-looking locusts behaving gregariously and vice versa.