CORRELATION BETWEEN ECDYSTEROIDS AND CUTICULOGENESIS IN NYMPHS OF THETICK ORNITHODOROS-PARKERI (ACARI, ARGASIDAE)

Ecdysteroids and cuticulogenesis were studied in third-instar nymphs o f the tick Ornithodoros parkeri Cooley. Ecdysteroid titer increases sl ightly during the postfeeding intermolt period, which correlates with the deposition of additional pro-cuticle lamellae. The titer increases at the time of apolysis, peaks at the time of epicuticle deposition, and then drops to a low but detectable level from the time of procutic le deposition until after ecdysis. Ecdysone and 20-hydroxyecdysone are the two major ecdysteroids present during the postfeeding intermolt p eriod and the period of epicuticle deposition. After ecdysis, the ecdy steroid immunoreactive material is composed principally of an unknown compound more polar than 20,26-dihydroxyecdysone and is found only in the midgut. This compound is possibly a metabolite of ecdysteroids lef t over from the previous instar.