An area-wide integrated tsetse eradication project was initiated in Zanzibar in 1994 by the International Atomic Energy Agency and the governments of Tanzania and Zanzibar, to eradicate Glossina austeni Newstead from Unguja Island (Zanzibar) using the sterile insect technique. Suppression of the tsetse population on Unguja was initiated in 1988 by applying residual pyrethroids as a pour-on formulation to livestock and by the deployment of insecticide impregnated screens in some of the forested areas. This was followed by sequential releases of gamma-sterilized male flies by light aircraft. The flies, packaged in carton release containers, were dispersed twice a week along specific flight lines separated by a distance of 1–2 km. More than 8.5 million sterile male flies were released by air from August 1994 to December 1997. A sterile to indigenous male ratio of >50:1 was obtained in mid-1995 and it increased to >100:1 by the end of 1995. As a consequence the proportion of sampled young females (1–2 ovulations), with an egg in utero in embryonic arrest or an uterus empty as a result of expulsion of a dead embryo, increased from 70% in the last quarter of 1995. In addition, the age structure of the female population became significantly distorted in favor of old flies (≥4 ovulations) by the end of 1995. The apparent density of the indigenous fly population declined rapidly in the last quarter of 1995, followed by a population crash in the beginning of 1996. The last trapped indigenous male and female flies were found in weeks 32 and 36, 1996, respectively. Time for 6 fly generations elapsed between the last catch of an indigenous fly and the end of the sterile male releases in December 1997.

https://bioone.org/journals/journal-of-economic-entomology/volume-93/issue-1/0022-0493-93.1.123/Glossina-austeni-Diptera--Glossinidae-Eradicated-on-the-Island-of/10.1603/0022-0493-93.1.123.pdf

Glossina austeni (Diptera: Glossinidae) eradicated on the island of Unguja, Zanzibar, using the sterile insect technique.

The taxonomic distribution and evolution of viviparity in Diptera is critically reviewed. The phenomenon ranges from ovoviviparity (eggs deposited at an advanced stage of embryonic development; larva emerges immediately after deposition), through viviparity (larva hatches inside female before deposition) to pupiparity (offspring deposited as pupa). Some Diptera are known to be facultatively viviparous, which is hypothesized to be a step towards the evolution of obligate viviparity. Obligate viviparity is found to comprise unilarviparity (single large larva in maternal uterus) which evolved many times independently, the rare oligolarviparity (more than one but not more than 12 larvae) and multilarviparity (large numbers of developing eggs or larvae in uterus) which is typical for the two largest clades of viviparous Diptera. Unilarviparity is either lecithotrophic (developing larva nourished by yolk of egg) or pseudo-placental (larva nourished by glandular secretions of mother). Viviparity has clearly evolved on many separate occasions in Diptera. It is recorded in 22 families, and this review identifies at least 61 independent origins of viviparity. Six families appear to have viviparity in their ground-plan. Some families have a single evolution of viviparity, others multiple evolutions. Guimaraes' model for the evolution of viviparity in Diptera is tested against phylogenetic information and the adaptive significance of viviparity is reviewed in detail. Possible correlations with life-history parameters (coprophily, parasitism, breeding in ephemeral plant parts, malacophagy and adult feeding habits – especially haematophagy) are analysed critically, as are potential advantages (shorter larval life, less investment in yolk by mother, protection of vulnerable stages, better access to breeding substrates, predation on competitors). Morphological constraints, adaptations and exaptations are reviewed, including the provision of an incubation space for the egg(s), the positioning of the egg(s) in the uterus, and maternal glands. The main morphological adaptations include greater egg size, reduction of egg respiratory filaments, thinning of chorion, modified larval respiratory system and mouthparts, and instar skipping. Female morphology and behaviour is particularly strongly modified for viviparity. The terminalia are shortened, the vagina is more muscular and tracheated, and the ovaries of unilarviparous species have a reduced number of ovarioles with alternate ovulation. Many of the final conclusions are tentative, and a plea is made for more detailed morphological and experimental study of many of the viviparous species. Viviparity in Diptera provides a fascinating example of multiple parallel evolution, and a fertile field for future research.

Ovoviviparity and viviparity in the Diptera

The age compositions of samples of females of Glossina pallidipes Aust, G palpalis fuscipes Newst and G brevipalpis Newst, are analysed by means of a method of age determination based upon the changes occurring in the reproductive system during successive gonotrophic cycles This method of age determination is described in detailFemales were sampled by three main methods: in traps, by catching on a bait-animal, and on a fly-round Some flies were also found as resting flies in the undergrowthTrap-caught samples of G pallidipes were older (ie), contained a larger proportion of old flies (and a smaller proportion of young flies) than the hand-caught samples The bait-caught samples were intermediate in age structure Correlated with the increasing mean age in the hand-caught—bait-caught—trap-caught series was an increase in the proportion of females carrying third-instar larvae and a decrease in the proportion of those carrying eggs Results with samples of G palpalis fuscipes and G brevipalpis were not so well definedThe results of dissecting teneral and non-teneral nullipars of G pallidipes and G palpalis fuscipes indicate that females of the latter are inseminated some time before they take their first blood-meal, but teneral females of G pallidipes are inseminated when they come to the host to feed or after they have fedThe relation of the ovarian method of age determination to Jackson's (1946) wing-fray categories in females of G pallidipes, and the probable epidemiological importance of the samples, are also discussed

Age determination for female tsetse flies and the age compositions of samples of Glossina pallidipes Aust., G. palpalis fuscipes Newst. and G. brevipalpis Newst.

Insect pest control programmes, which integrate the release of sterile insects, can be efficient only if the released insects have an optimal biological quality. Frequent monitoring of the quality of reared insects after being released in the field is an important but often neglected component of area-wide integrated pest management (AW-IPM) programmes that integrate the sterile insect technique (SIT). Parameters of sterile insects, which should be monitored regularly, are sexual competitiveness of the released insects, and related components, e.g. survival, mobility, dispersal characteristics, and spatial occupation of the habitat. A well-balanced monitoring programme will, at any given time, provide essential feedback on the progress being made. This information is prerequisite to efficient implementation of the release and cost-efficient use of sterile insects. The type of monitoring to be done will be determined largely by the particular biology of the target insect species. The most important parameter in relation to the release of sterile insects is the rate of sterility induced in the wild insect pest population; it will provide the best evidence that any observed changes, e.g. in the density of the target insect, are caused by the release of sterile insects.

Monitoring Sterile and Wild Insects in Area-Wide Integrated Pest Management Programmes

A field trial was carried out in a Maasai group ranch to assess the use of odour-baited traps for suppression of a population of the tsetse fly Glossina pallidipes Austen. In January, 1987, local people made 100 NG2B traps in their homesteads. These were then deployed within the suppression zone of about 100 km2, primarily in the areas of woodland where flies aggregate in the dry season. Traps were baited with acetone (ca. 150 mg/h) and cow urine (ca. 1000 mg/h) and checked at monthly intervals in order to replenish odours and repair damage. A further 90 traps were added between October and December to enlarge the suppression area slightly and to strengthen the trap barriers. The population was monitored using biconical and NG2B traps as well as by mark-release-recapture estimates of population size. By October the number of G. pallidipes in the suppression zone was reduced by 98–99% relative to the number 3 km outside the suppression zone. Some reinvasion, mainly of parous females, occurred in November during the short rains but these flies were rapidly trapped out again. Average mortality rates due to trapping were estimated at 4–5% per day, which, combined with the natural mortality, reduced the adult population at a rate of about 2.6% per day during the dry season. The traps had less effect on the smaller population of G. longipennis Corti but still gave a reduction of up to 90% in the dry season. The use of this low technology approach offers good prospects for future community-based tsetse control operations.

Control of tsetse fly (Diptera: Glossinidae) populations using traps at Nguruman, south-west Kenya.

The ovulation cycle in glossina morsitans westwood (diptera: muscidae) and a possible method of age determination for female tsetse flies by the examination of their ovaries

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The ovulation cycle in glossina morsitans westwood (diptera: muscidae) and a possible method of age determination for female tsetse flies by the examination of their ovaries