Descriptions and morphometrics of the nymphs of Zonocerus variegatus (L.) (Orthoptera: Acridoidea)

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Abstract
The nymphal instars of Zonocerus variegatus (L.) are described from insects collected near Ibadan, Nigeria. Most insects reared in the laboratory passed through six nymphal instars, although more had only five nymphal instars when reared in crowded conditions. The proportions with five or six instars were not altered by different food-plants. Femur length, head width and pronotal length of laboratory-reared insects were measured. The sizes were only slightly affected by food-plants; they fall into fairly discrete classes corresponding with each instar. The form of antennae, genitalia and wing pads in successive instars is also described. The early-instar nymphs are almost entirely black, with a few yellow markings. In later instars, the extent of the yellow increases. Field data from insects collected during the dry season can be interpreted on the basis of the laboratory studies and indicate that most insects in the field pass through six nymphal instars. More data are needed before nymphs collected in the wet season can be characterised with certainty.