Sexual maturation and ovarian activity in Rhammatocerus schistocercoides (Orthoptera: Acrididae), a pest grasshopper in the state of Mato Grosso in Brazil

Sexual maturation and ovarian activity were studied in Rhammatocerus schistocercoides (Rehn, 1906) under natural conditions in the state of Mato Grosso in Brazil, a recognized outbreak area of this species. The end of the dry season marks the onset of sexual maturation, which could be associated with the photoperiod but not with the arrival of the 1st rains. This means that sexual maturation, although triggered at a set date, progresses under highly varied ecological conditions. This must have an important impact on ovarian activity and thus on the quantity of the eggs laid. Interannual fire and precipitation variations could modify population levels (through effects on ovarian activity, and also on the embryonic development success rate) and explain the outbreak cycles. Vitellogenesis failures were noted by frequently marked oocyte resorptions; an indication that the environmental conditions are not always optimal for egg maturation. Conditions during this study, at the beginning of the 1994-1995 rainy season, were not entirely favorable because ovarian yield was only 59%. Pseudocorpora lutea were noted at the base of the ovarian pedicels, which has to our knowledge never been reported. They slightly complicated the current study and have been a source of confusion in the past