Variation of the Oviposition Preferences of Aedes aegypti in Function of Substratum and Humidity

Abstract

1981and 1998(Teixeira et al. 1999, after decades of absence (Schatzmayr 2000). The ovipositing habit of this mosquito is still little understood. In the case of Brazil, the few studies on the ovipositing behaviour of this insect were conducted on a population that has already been eradicated, and the current population may be of a different origin, thus not presenting the same behaviour as observed previously. Variations have been observed in terms of life span and the number of eggs produced by females of 13 different populations of A. aegypti from Africa, Asia and America (Crovello & Hacker 1972). The site chosen for laying eggs at the breeding sites is of great importance for the biology of the mosquito. Most eggs have been found to be laid above the water line and only a few eggs are laid on the water surface (Young 1922, Goma 1964, Chadee et al. 1995 and the choice of oviposition site is genetically controled (Schoenig 1968).Oviposition occurs on the water surface when the surface of the container does not enable the adherence of the female tarsi during oviposition (Christophers 1960). A study conducted in Manaus (Amazonas, Brazil) showed that non-submersed eggs did not hatch, in contrast to those on the water surface that were submersed (Young 1922). The habit to lay eggs on the water surface, as well as the occurrence of hatching without submersion has rarely been observed in A. aegypti (Christophers 1960 developed to determine the existence of adult females in the environment (Fay & Perry 1965). Today, this trap is used in several countries to determine infestation rates and to evaluate the efficacy of the control measures adopted (Reiter & Gubler 1997). Variations in the site chosen for oviposition have been observed within the species. In a study conducted in Australia, most eggs were found to be laid on the water surface instead of a porous and humid surface (O'Gower1957, 1963. However, these studies did not take in consideration the physiological age of the females. Observations made at two locations in Brazil on A. aegypti breeding sites in residences with plant-containing vases (unpublished data) showed a large number of eggs on the water surface, the magnitude for these variations are not clear in Brazilian A. aegypti.The objectives of the present investigation were to study the oviposition behaviour of two mosquito populations in three different types of breeding sites, two of them commonly found in residences, at two different humidity levels, to determine the influence of female density on this behaviour and to evaluate the hatching response of eggs on the water surface. MATERIALS AND METHODSMosquito population and laboratory rearing -The laboratory populations were formed from eggs and larvae collected at 30 residences in each of two cities (Botucatu, 22º53'9"S 48º26'42"W and Lins, 21º40'43"S 49º44'33"W) in the State of São Paulo, Brazil, respectively called B and L. The eggs and larvae obtained from ovitraps and potted plants were maintained in the laboratory at 25 o C, at a photoperiod o...

Epidemiological and ecological determinants of Zika virus transmission in an urban setting

“…Rainfall is assumed to affect positively the fraction of eggs that successfully hatch ($c^v$) (Alto and Juliano, 2001; Rossi et al, 2015; Tran et al, 2013; Madeira et al, 2002). A similar positive relationship is taken for the vector biting rate ($a^v$) and humidity levels (Yasuno and Tonn, 1970), in contrast to a negative effect on the adult mosquito mortality rate (${\mu }_V^v$) (Alto and Juliano, 2001).…”

Environmental drivers for Coquillettidia mosquito habitat selection: a method to highlight key field factors

“…The CCA revealed that a high level of atmospheric humidity, most likely maintained by the vegetation cover on the bank, was a factor supporting Coquillettidia female choice. This factor is not specific to Coquillettidia species, and it is an ecological parameter involved in the selection of oviposition site for several mosquito species such as Aedes (Madeira et al, 2002) and Toxorhynchites (Jordan, 1992).…”

Aedes aegypti eggs oviposited on water surface collected from field ovitraps in Nova Iguaçu City, Brazil

“…We suspect that this paddle rejection might be due to the presence of kairomone left by predators or natural enemies such as ants or cockroaches, or the eggs might have been attacked by these predators while they were on the paddles. Madeira et al (12) witnessed this incidence in the fi eld, and this event might likely be quite common in nature. Soares et al (15) also found eggs only in the water, but at a lower percentage (23 of 500 surveys = 4.6%).…”

“…Soares et al (15) found 11.2% of all eggs in the water in 96% of the fi eld traps and reported signifi cant increase in the number of eggs in the water when the relative humidity dropped below 40%. In the laboratory, Madeira et al (12) also showed that, at lower humidity, females oviposited more eggs on the liquid surface. Gomes et al (13) conducted a laboratory experiment and indicated that eggs oviposited on water surface showed faster eclosion and argued that this particularity in the environment could lead to faster colonization.…”

“…However, most observations of eggs on water surface were conducted in laboratories (5) (6) (7) (8) (9) (10) (11) (12) (13) , and few fi eld observations were only accomplished by Chadee et al (14) in Trinidad and, more recently, by Soares et al (15) in a small town in Brazil (30,716 inhabitants) within a semiarid area. All the studies accomplished in Brazil (12) (13) (15) , suggest the relevance of the eggs deposited on water surface for controlling actions. Soares et al (15) found 11.2% of all eggs in the water in 96% of the fi eld traps and reported signifi cant increase in the number of eggs in the water when the relative humidity dropped below 40%.…”