Field trials of various models of the pyramid trap on Glossina palpalis in the Congo

Preliminary trials of 12 models of the pyramid trap were carried out in the Congo on Glossina palpalis palpalis (Robineau-Desvoidy) using Latin square designs. The models were compared with the standard trap with which they differed either in the shape of the pyramid, the addition of a royal blue cloth skirt, or the pattern of the blue-black screen. A decrease in height and/or volume of the pyramid significantly reduced the capture rate. The standard tetrahedral pyramid was significantly superior to both the regular tetrahedral and the trihedral pyramid. The addition of a royal blue cotton skirt modified both the attractiveness and effectiveness of the trap. However, although the attractiveness was probably increased, the skirt may have deterred the flies from entering the pyramid; the best results were obtained with the largest openings. The modification of the blue-black screen pattern may be a way to increase the attraction of flies to the trap. Although no model was found to be significantly superior to the standard, certain gave interesting results which should be investigated further.

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Résumé Des essais de 12 variants du piège pyramidal ont été réalisés au Congo selon le protocole expérimental des carrés latins, sur Glossina palpalis palpalis (Rob.-Desv.). Les variants ont tous été comparés au modèle standard dont ils diffèrent soit par la forme de la pyramide, soit par l'adjonction d'une juppe de tissu bleu, soit par la recombinaison des parties bleues et noires des écrans. Les résultats ont montré le rôle particulier de ces différents composants du piège au niveau de l'attraction et de l'efficacité à la capture. Les modifications de la hauteur et du volume de la pyramide ont diminué significativement l'efficacité du système de capture, soit en rendant plus difficile l'accès de ce système au tsétsé, soit en leur facilitant la sortie de la pyramide. L'addition d'une jupe de tissu bleu modifie ces deux aspects à la fois, mais, si elle augmente probablement l'attractivité, la jupe de certains modèles gène la pénétration des mouches à l'intérieur de la pyramide. Le réagencement de la couleur bleue et noire des écrans pourrait accroître l'attraction de la mouche ou favoriser son ascension. Bien qu'aucun modèle ne soit apparu significativement supérieur au standard, certains de ceux-ci ont donné des résultats intéressants. Ces modifications constituent donc des voies à explorer, notamment en confrontant ces modèles avec d'autres espèces de tsétsé et dans d'autres environements.

     

Influence of temperature changes on larviposition rhythm in the tsetse fly, Glossina morsitans

ABSTRACT. The hourly and quarter-hourly distribution of larval deposition by female Glossina morsitans Westw. was studied at various temperatures. At constant temperature and humidity, peak larviposition occurred 8–9 h after lights on. The effect of confining the flies to daily (LD 12:12 h) regimes of at least twenty-five consecutive cycles that included a sudden increase in temperature of c. 6°C for 2 h was a significant reduction in depositions during each period of increased temperature, and a significant increase before the heat impulse. When the temperature was allowed to fall rapidly, larviposition rate doubled in the following 15 min.     

Variations in attack behaviours between Glossina palpalis gambiensis and G. tachinoides in a gallery forest suggest host specificity

Tsetse flies Glossina palpalis gambiensis and G. tachinoides are among the major vectors of sleeping sickness (Human African Trypanosomiasis‐HAT) and nagana (African Animal Trypanosomiasis – AAT) in West Africa. Both riparian species occur sympatrically in gallery forests of south west Burkina Faso, but little is known of their interspecies relationships although different authors think there may be some competition between them. The aim of this study was to check if sympatric species have different strategies when approaching a host. A man placed in a sticky cube (1 m × 1 m × 1 m) and a sticky black‐blue‐black target (1 m × 1 m) were used to capture tsetse along the Comoe river banks in a Latin Square design. The number and the height at which tsetse were caught by each capture method were recorded according to species and sex. Glossina p. gambiensis was more attracted to human bait than to the target, but both species were captured at a significantly higher height on the target compared with the human bait (P < 0.05). No significant difference in heights was found between G. tachinoides and G. p. gambiensis captured on targets (33 and 35 cm, respectively, P > 0.05). However, catches on human bait showed a significant difference in height between G. tachinoides and G. p. gambiensis (22.5 and 30.6 cm, respectively, P < 0.001). This study showed that these sympatric species had different attack behaviours to humans, which is not the case with the target. The implications of these findings are discussed.     

A comparison of phototactic responses to red and green light in Glossina morsitans morsitans and Musca domestica

ABSTRACT. Experiments were performed on male Glossina morsitans morsitans Westw. and female Musca domestica L. to investigate their phototactic responses at long wavelengths. In both species, green light was less attractive than red (relative to a 400 nm standard). In M. domestica this can be adequately explained by an intensity-dependent phototactic reversal at wavelengths above 500 nm; red light could be matched in attractiveness by a low intensity green light, implying that no true red-green discriminating ability exists, but that red is perceived as a dim green. Although a partial phototactic reversal was also observed in G. m. morsitans at 525–575 nm, no tested intensity of green matched red in attractiveness. It appears therefore that G. m. morsitans may be an unusual dipteran in possessing a method of discriminating red and green light independently of intensity. Both species also resolved near-UV from green.     

Determining the age of adult male and female Glossina morsitans morsitans using a new technique

Abstract. 1. Pteridines accumulated linearly with age up to at least 63 days in male and 140 days in female Glossina morsitans morsitans Westwood kept under laboratory conditions. Time is the major factor influencing total pteridine accumulation levels with the accumulation rate being modulated by temperature.
2. It is suggested that pteridine accumulation may be used to determine the age of male and female tsetse flies in the field.     

Seasonal distribution and abundance of tsetse flies (Glossina spp.) in the Faro and Deo Division of the Adamaoua Plateau in Cameroon

Ten years after the large-scale tsetse control campaigns in the important cattle rearing areas of the Faro and Deo Division of the Adamaoua Plateau in Cameroon, the seasonal distribution and abundance of tsetse flies (Glossina spp.) were determined. During a period of 12 consecutive months (January-December 2005), the tsetse population was monitored along four trap transects consisting of a total of 32 traps and two flyround transects traversing the study area, which comprised the tsetse-infested valley, a buffer zone and the supposedly tsetse-free plateau. Throughout the study period, a total of 2195 Glossina morsitans submorsitans and 23 Glossina tachinoides were captured in the traps and 1007 G. m. submorsitans (78.8% male flies) were captured along the flyround transects. All G. tachinoides and almost all G. m. submorsitans were captured in the valley. Five G. m. submorsitans were captured in traps located in the buffer zone, whereas no flies were captured in traps located on the plateau. The index of apparent abundance (IAA) of G. m. submorsitans was substantially higher in the areas close to game reserves. In the remaining part of the valley, where wildlife is scarce and cattle are present during transhumance (dry season), the IAA of tsetse was substantially lower. In this part of the valley, the abundance of tsetse seemed to be associated with the presence of cattle, with the highest IAA during transhumance when cattle are present and the lowest apparent abundance during the rainy season when cattle have moved to the plateau. It is concluded that the distribution of tsetse in a large part of the valley undergoes substantial seasonal changes depending on the presence or absence of cattle. The repercussions of those findings for the control of tsetse in the valley and the probability of reinvasion of the plateau are discussed.     

Cloning and expression of the yolk protein of the tsetse fly Glossina morsitans morsitans

Two major families of nutritional proteins exist in insects, namely the vitellogenins and the yolk proteins. While in other insects only vitellogenins are found, cyclorraphan flies only contain yolk proteins. Possible sites of yolk protein synthesis are the fat body and the follicle cells surrounding the oocyte. We report the cloning of the yolk protein of the tsetse fly Glossina morsitans morsitans, a species with adenotrophic viviparity. The tsetse fly yolk protein could be aligned with other dipteran yolk proteins and with some vertebrate lipases. In contrast to the situation in most fly species, only a single yolk protein gene was found in the tsetse fly. Northern blot analysis showed that only the ovarian follicle cells, and not the fat body represents the site of yolk protein synthesis.     

Genetic differentiation of some Glossina morsitans morsitans populations

To study the population structure of Glossina morsitans morsitans Westwood (Diptera: Glossinidae), polymerase chain reaction (PCR) and singlestrand conformational polymorphism (SSCP) methods were used to estimate mitochondrial DNA diversity at four loci in six natural populations from Zambia, Zimbabwe and Mozambique, and in two laboratory cultures. The Zambian and Zimbabwean samples were from a single fly belt. Four alleles were recorded at 12S and 16S1, and five alleles at 16S2 and COI. Nucleotide sequencing confirmed their singularities. Chi-square contingency tests showed that allele frequencies differed significantly among populations. Mean allele diversities in populations averaged over loci varied from 0.14 to 0.61. Little loss in haplotype diversity was detected in the laboratory cultures thereby indicating little inbreeding. Wright's fixation index F(ST) in the natural populations was 0.088+/-0.016, the correlation of haplotypes within populations relative to correlations in the total. A function of its inverse allows an estimate of the mean equivalent number of females exchanged per population per generation, 5.2. No correlation was detected between pairwise genetic distance measures and geographical distances. Drift explains the high degree of differentiation.     

Environmental information systems for the control of arthropod vectors of disease

Over the last decade, remote sensing technologies and geographical information systems have moved from the research arena into the hands of vector control specialists. This review explains remote sensing approaches and spatial information technologies used for investigations of arthropod pests and vectors of diseases affecting humans and livestock. Relevant applications are summarized with examples of studies on African horse sickness vector Culicoides midges (Diptera: Ceratopogonidae), malaria vector Anopheles and arbovirus vector culicine mosquitoes (Diptera: Culicidae), leishmaniasis vector Phlebotomus sandflies (Diptera: Psychodidae), trypanosomiasis vector tsetse (Diptera: Glossinidae), loaiasis vector Chrysops (Diptera: Tabanidae), Lyme disease vector Ixodes and other ticks (Acari: Ixodidae). Methods and their uses are tabulated and discussed with recommendations for efficiency, caution and progress in this burgeoning field.