Initiation of oocyte development in Varroa jacobsoni depends on whether the female enters the brood cell of Apis mellifra before operculation and subsequently sucks hemolymph from a late fifth instar bee larva. Females inserted into the brood 24 h after cell capping, during the spinning phase of the bee larva, do not initiate oocyte development. All stages of mite vitellogenesis and embryogenesis which are described here develop in a close temporal relation to the host stages. A timetable of the first gonocycle is given showing its duration in worker and drone host cells. About 70 h after capping of the bee brood cell, the first egg is laid containing a nearly completed protonymph that hatches within the next day.*The term gonocycle is used here for the development of the oocyte and the embryo until oviposition of the ovoviviparous egg. In case of this mite, only one offspring per gonotrophic cycle is produced. Several overlapping gonocycles occur within one reproductive phase identical with the postcapping period in preimaginal development of the honey bee host. Downloaded by [University of Toronto Libraries]

Adult females of the mosquito Aedes aegypti showed two cycles of DNA replication in the fat body based on microspectrophotometric measurement of changes in nuclear DNA. The first cycle began after emergence and resulted in 80% of diploid fat body cells becoming tetraploid and 20% becoming octoploid by the end of the third day. The second replication cycle occurred h after a blood meal and resulted in an increase in octoploid nuclei to 67%.Topical application of juvenile hormone or methoprene to abdomens isolated at emergence stimulated an increase in ploidy levels above that normally seen in situ. Synthesis of DNA, estimated by incorporation of injected [3H]-thymidine, rose after emergence and remained high for 2 days. Synthesis increased again after a blood meal, reached a peak by 6 h, and returned to low levels by 24 h after the meal. The timing of DNA synthesis and a measurable increase in ploidy were temporally separated. The ploidy increase, but not DNA synthesis, was correlated with increases in juvenile hormone levels.

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The motile behaviour of mitochondria in the ovarian trophic cord of the red cotton bug, Dysdercus intermedius, was observed optically using video-enhanced differential interference contrast (AVEC-DIC) microscopy. The motion of 258 video-recorded mitochondria was analysed of which 10%-30% were found to move during the observation periods. Of the moving mitochondria 76% travelled towards the oocyte with an average velocity of 3.37 μm/ min, and 24% towards the tropharium with 2.84 μm/min. The movement was found to be basically of the saltatory type I as known from nerve axons characterized by the absence of directional reversal. In some cases short periods of interrupted motion of type II, i.e. with local oscillations, were observed. Individual mitochondria often showed velocity variations during the excursions. The hemipteran trophic cords are known to contain numerous parallel microtubules. As the observed type of mitochondrial motility resembles axonal transport, a modified transport hypothesis is presented for the microtubule-based motility of organelles in the nurse strands of telotrophic insect ovarioles.