Life Cycle

The biology of each species of sand fly is unique and complex, including reproduction, feeding, dispersal and other activities, and being of importance for the epidemiology of transmitted diseases and vector control (WHO, 1990). 

Sand flies undergo complete metamorphosis, passing through four distinct stages during their life cycle: egg, larvae, pupa, adult / imago. 

In arid and temperate regions, larvae may remain in a state of diapause for many months. In temperate countries, sand flies over-winter as eggs or larvae in a so-called diapause. For this reason, adults can appear early in summer, and leishmaniosis – as one the sand fly-borne diseases – can exist in places with a cold winter (Lewis, 1971). Similarly, diapause might also be the means by which many tropical sand flies survive periods of drought or heavy rain (Ward and Killick-Kendrick, 1974). 

Palaearctic sand flies over-winter as fourth instar larvae (Killick-Kendrick and Killick-Kendrick, 1987; Ready and Corset, 1980). From laboratory studies, a complete gonotrophic cycle is normally not less than 6 weeks, but can differ between different species (Killick-Kendrick and Killick-Kendrick, 1999). 

Egg

Eggs are oblong-oval, minute (average 0.3-0.4 mm according to Shevchenko, 1929) and difficult to find in nature. Newly-laid eggs are soft, light yellow, with a shiny surface. After several hours they darken, become hard, dark brown and show characteristic thin ridges (Perfiliev, 1968). 

They are laid in cracks and crevices in moist ground, among leaf litter, between buttress roots of trees, at the bases of termite mounds, on stable floors and in poultry sheds, where adult flies rest and the microclimate is high. 

The site and type of habitat is species-dependent. Between 10/15 and 100 eggs are laid in a single batch (40-70 usually in one oviposition cycle (WHO, 1990)). Under optimum conditions they hatch in 6-17 days. Longer periods are necessary in cooler conditions. 

Larva

Sand fly larvae possess one respectively two pairs of caudal bristles and characteristic 'matchstick' hairs on each segment. 

Four instars of larvae follow over a period of 21-60 days (Peters, 1992) / 16-90 days (Service, 2001). Larvae are mainly scavengers. In laboratories, they are fed on semi-rotting vegetable matter and decomposing arthropod bodies, chow or even faeces of vertebrates (e.g. aged rabbit faeces (Singh, 1985, based on Endris et al. 1982)). The developing larva is cutting an exit hole with a sort of 'egg tooth' into the egg shell. 

The final-instar larva sheds its skin and the pupa is formed. Larval breeding sites are seldom found, Bettini and Melis (1988) suggested pre-imaginal stages associated with a comparatively stable, cool, humid environment, protected from rain and sunshine and in the special analyzed site, rich in clay and organic nitrogen. 

Pupa

The pupae of sand flies are 3 mm long and club-shaped. The narrow part is curved and the head and thorax are curved backwards. The posterior segments are covered with the exuviae of the fourth-stage larva. With it the pupa is attached to the substrate in a usually vertical position (Perfiliev, 1968). After approximately 5-10 days the adult emerges. 

Adult

Adults can be identified from other insects by their behaviour, appearance, size etc. (see Morphology). Both sexes feed on plant sugars (Lewis and Domoney, 1966) and possibly also honeydew of aphids and coccids (Killick-Kendrick, 1979). The type of sugar and the frequency of uptake may be a factor in the insect's ability to transmit Leishmania. Plant sugars may be essential for parasite survival, and promastigotes require carbohydrates for their development (Killick-Kendrick, 1978). Only females feed on blood, which is suspected as a source of protein for egg development. When seeking food sand flies normally have a characteristic short hopping flight. 

Females require the blood meal to mature about 80-100 eggs and the time from engorgement to oviposition is not less than 6 days (demonstrated in Mediterranean species) (Killick-Kendrick and Killick-Kendrick, 1999). Males are attracted to females when those are feeding and will mate with them even while the females are taking a blood meal. 

The life expectancy has hardly been determined for wild female sand flies, but Killick-Kendrick et al. (1984) recaptured marked Ph. ariasi 28 days after release. 

In nature, more than one gonotrophic cycle is considered normal (Dolmatova, 1942), whereas in the laboratory, most gravid females lay eggs and die either as they lay or shortly afterwards. For some subgenera of Phlebotomus the females are gonotrophically concordant and take one blood meal each gonotrophic cycle (Killick-Kendrick and Killick-Kendrick, 1999). 

Most Leishmania species complete their life-cycle within a single ovarian cycle of the sand fly, and parasites may therefore be transmitted at the first bloodmeal after an infective feed. But in some (Leishmania donovani donovani and some strains of L. donovani infantum) the development is not complete until after the second bloodmeal. 

References

Introduction

Killick-Kendrick R,Killick-Kendrick M: The laboratory colonization of Phlebotomus ariasi (Diptera: Psychodidae). Ann Parasitol Hum Comp. 1987, 62, 354-6

Killick-Kendrick R, Killick-Kendrick M: Biology of sand fly vectors of Mediterranean canine leishmaniosis. In: Killick-Kendrick R (ed.): Canine leishmaniasis: an update. Proc. Int. Can. Leishm. Forum, Barcelona, Spain, 1999, Intervet Int., Boxmeer, The Netherlands, 1999, 26-31 

Lewis DJ: Phlebotomid sandflies. Bull. WHO 1971, 44, 535-51

Ready PD, Croset H: Diapause and laboratory breeding of Phlebotomus perniciosus Newstead and Phlebotomus ariasi Tonnoir (Diptera: Psychodidae) from southern France. Bull Ent Res. 1980, 70, 511-23 

WHO: Control of the leishmaniases. Report of a WHO Expert Committee, Tech. Rep. Ser. No. 793, WHO, Geneva, 1990

 

Egg

Perfiliev PP: Fauna of U.S.S.R. Diptera. Phlebotomidae (sandflies). Acad. Sci. U.S.S.R. Zool. Inst. New Ser. No. 93, Vol. 3 No. 2, Israel Program for Scientific Translations, Jerusalem, 1968  

Shevchenko FI: Vneshnyaya morfologiya lichinok moskitov. P. papatasi, P. chinensis, P. sergenti (The external morphology of sandfly larvae (P. papatasi, P. chinensis, P. sergenti)). Meditsinskaya Mysl' Uzbekistana I Turkmenistana, 1929-1930, 67-83 

WHO: Control of the leishmaniases. Report of a WHO Expert Committee, Tech. Rep. Ser. No. 793, WHO, Geneva, 1990  

 

Larva

Bettini S, Melis P: Leishmaniasis in Sardinia. III. Soil analysis of a breeding site of three species of sandflies. Med Vet Entomol. 1988, 2, 67-71 

Endris RG, Perkins PV, Young DG, et al.: Techniques for laboratory rearing of sand flies (Diptera: Psychodidae). Mosq News.1982, 42, 400-7

Peters W: Leishmaniases. In: Peters W (ed.): A colour atlas of arthropods in clinical medicine. Wolfe Publish. Ltd., London, 1992, pp. 115-34

Singh P: Multiple-species rearing diets. Diptera: Psychodidae. In: Singh P, Moore RF (eds.): Handbook of Insect Rearing. Vol. 1 Elsevier, Amsterdam, 1985, pp. 33-4 

Service MW: Phlebotomine sand-flies (Phlebotominae). In: Service MW (ed.): The encyclopedia of arthropod-transmitted infections. CABI Publish., Oxon, New York, 2001, pp. 395-7 

 

Pupa

Perfiliev PP: Fauna of U.S.S.R. Diptera. Phlebotomidae (sandflies). Acad. Sci. U.S.S.R. Zool. Inst. New Ser. No. 93, Vol. 3 No. 2, Israel Program for Scientific Translations, Jerusalem, 1968  

 

Adult

Dolmatova AV: Life cycle of Phlebotomus papatasi (Scopoli). (in Russian) Med Parazit. (Mosk.) 1942, 11, 32-70 

Killick-Kendrick R: Recent advances and outstanding problems in the biology of phlebotomine sandflies. Acta Trop. 1978, 35, 297-313

Killick-Kendrick R: Biology of Leishmania in phlebotomine sandflies. In: Lumsden WHR, Evans DA (eds.): Biology of the Kinetoplastida. Vol. 2, Academic Press, London, New York, 1979, pp. 395-460 

Killick-Kendrick R, Killick-Kendrick M: Biology of sand fly vectors of Mediterranean canine leishmaniosis. In: Killick-Kendrick R (ed.): Canine leishmaniasis: an update. Proc. Int. Can. Leishm. Forum, Barcelona, Spain, 1999, Intervet Int., Boxmeer, The Netherlands, 1999, 26-31 

Killick-Kendrick R, Rioux JA, Bailly M, et al.: Ecology of leishmaniasis in the south of France. 20. Dispersal of Phlebotomus ariasi Tonnoir, 1921 as a factor in the spread of visceral leishmaniasis in the Cévennes. Ann Parasitol Hum Comp. 1984, 59, 555-72 

Lewis DJ, Domoney CR: Sugar meals in Phlebotominae and Simuliidae. Proc R Ent Soc Lond. A 1966, 41, 175-79 

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