Review of semiochemicals that mediate the oviposition of mosquitoes: a possible sustainable tool for the control and monitoring of Culicidae

The choice for suitable places for female mosquitoes to lay eggs is a key-factor for the survival of immature stages (eggs and larvae). This knowledge stands out in importance concerning the control of disease vectors. The selection of a place for oviposition requires a set of chemical, visual, olfactory and tactile cues that interact with the female before laying eggs, helping the localization of adequate sites for oviposition. The present paper presents a bibliographic revision on the main aspects of semiochemicals in regard to mosquitoes' oviposition, aiding the comprehension of their mechanisms and estimation of their potential as a tool for the monitoring and control of the Culicidae.

Infestation of Aedes aegypti estimated by oviposition traps in Brazil

OBJECTIVE: To assess infestation levels of Aedes aegypti using the oviposition trap (ovitrap) method and to compare these results with data obtained with the use of indices traditionally applied in public programs aimed at fighting this vector. METHODS: Nine sentinel areas in Northeastern, Brazil, were assessed and infestation levels were measured for a nine-month period. Egg density and container indices were estimated and compared with previous results found using the house index and Breteau index. RESULTS: The results indicated that the area studied was infested with this vector during the entire study period and that the infestation was widespread in all areas. Different results were found with the different indices studied. There were areas in which the house index and the Breteau index were negative or close to zero, whereas the container index for the same area was 11% and the egg density index was 8.3%. CONCLUSIONS: The container and egg density indices allow better assessment of infestation rates in a city than the conventionally used indices (house index and Breteau index). At lower operational costs and easier standardization, these indices can be applied as a measurement tool for assessing infestation rates during entomological surveillance in programs to fight Aedes aegypti.

Caffeine effect on mortality and oviposition in successive generations of Aedes aegypti

OBJECTIVE: Previous experiments showed that caffeine blocks the development of Aedes aegypti (Diptera, Culicidae) in the larval stage, consequently inhibiting the production of adults. This study aimed at obtaining data suggestive of caffeine resistance by these mosquitoes. METHODS: Experiments were carried out in successive generations to assess adult production from eggs laid in previous generation and oviposition rate in every generation using 200 and 500 µg/mL caffeine. Tap water was used as control. Experiments were conducted in the city of São José do Rio Preto, Southeastern Brazil between 2002 and 2005. Statistical tests consisted of exploratory data analysis and smoothing algorithms. RESULTS: Increasing reduction in productivity of adults occurred among generations at both caffeine concentrations but the differences were only significant at 200µg/mL caffeine. As for the oviposition rate, there was a decrease in the mean number of eggs per female over generations at both caffeine concentrations. CONCLUSIONS: There was no evidence of caffeine resistance over generations. The study results corroborate caffeine as an alternative as an important Ae. Aegypti control agent to avoid resistance.

Oviposition by Schistosoma mansoni during in vitro cultivation

Observation of Schistosoma mansoni oviposition during in vitro culture of adult worms for a maximum period of 10 days showed three well distinct phases in the kinetics of oviposition: an initial phase with low egg production, a period of maximum oviposition and finally a progressive reduction in the number of eggs during the late phases of culture. The kinetics of oviposition and the number of eggs laid by the parasites are influenced by the number of worm pairs per amount of RPMI 1640 medium, time of parasite development in the vertebrate host and type of serum utilized in the culture medium.

Oviposition preference hierarchy in Ceratitis capitata (Diptera, Tephritidae): influence of female age and experience

The influence of two factors, age and previous experience, on the oviposition hierarchy preference of Ceratitis capitata (Wiedemann, 1824) females was studied. Two populations were analyzed: one reared in laboratory during 17 years and the other captured in nature. In the first experiment the oviposition preference for four fruits, papaya, orange, banana and apple was tested at the beginning of oviposition period and 20 days past. The results showed that the wild females as much the laboratory ones had an oviposition preference hierarchy at the beginning of peak period of oviposition. However this hierarchic preference disappeared in a later phase of life. In the second experiment the females were previously exposed to fruits of different hierarchic positions and afterwards their choice was tested in respect to the oviposition preference for those fruits. The results showed that there was an influence of the previous experience on the posterior choice of fruits to oviposition when the females were exposed to fruits of lower hierarchic position.

Oviposition behavior of Zabrotes subfasciatus females (Coleoptera, Bruchidae) under conditions of host deprivation

Oviposition of Zabrotes subfasciatus (Boheman, 1833) on Phaseolus vulgaris (Linnaeus, 1753) was studied immediately after emergence of the adults throughout the females life and in situations of host deprivation lasting for 1 to 10 days. The number of eggs laid daily, longevity, duration of oviposition and distribution of eggs per grain were studied. The number of eggs laid per day varied significantly, with the oviposition peak in the presence of the host (control group) occurring between day 2 and day 5 of oviposition. In the absence of the host, a shift in the oviposition peak to the first day after deprivation was observed, except for the group deprived for one day which showed a peak between days 1 and 4 after introduction of the host. The distribution of the eggs per grain in the control group and in the groups deprived of the host for 2, 5, 8 and 10 days, a larger egg aggregation was observed for all deprived groups compared to the control group.

Oviposition behaviour of Gryon gallardoi (Hymenoptera, Scelionidae) on eggs of different ages of Spartocera dentiventris (Hemiptera, Coreidae)

The oviposition behaviour of Gryon gallardoi (Brèthes, 1914) on eggs of Spartocera dentiventris Mendonça Jr. (Berg, 1884) of different ages (2, 3, 4, 5, 6, 7, 8 and 12 days) was investigated. Groups of 12 eggs of each age were exposed to single females of G. gallardoi, and the oviposition behaviour was recorded under a stereomicroscope for two hours. Ten replicates were used for each age. In order to identify the moment the parasitoid egg was released inside the host, 1-day old eggs of S. dentiventris were exposed to G. gallardoi females, and the oviposition was interrupted at intervals of 20, 40, 60, 80, 100, 120, 140 and 160s after ovipositor insertion had initiated. Five behavioural steps were recorded: drumming, ovipositor insertion, marking, walking and resting. The average drumming and ovipositor insertion times increased with the host age (P<0.01). Ovipositor insertion usually occurred next to the longitudinal extremities of the host eggs. Marking took on average 19.5 ± 0.7s, and as walking and resting, was not affected by host age. Self-parasitism behaviour was observed in only 13.8 ± 2.3% of the eggs, being more evident with increasing patch depletion (reduction in non-parasitized eggs in the egg group, P<0.01), again with no variation due to changes in host egg age. For all ages tested, self-parasitized host eggs were less frequently contacted and accepted than non-parasitized ones (P<0.01). The parasitoid egg was released 137.0 ± 3.7s after ovipositor insertion. Spartocera dentiventris egg condition can lead to parasitoid behavioural changes, especially during the process of host choice and discrimination.

Oviposition behavior of wild Zabrotes subfasciatus (Coleoptera, Chrysomelidae) females deprived of the host Phaseolus vulgaris (Fabaceae)

The insects oviposition behavior is fundamental to study population dynamics, life history evolution, insect-plant and parasitoid-host interactions. Zabrotes subfasciatus (Boheman, 1833) females oviposition behavior in the presence and absence of a host is unknown. The main objective of this study was to describe in detail the oviposition behavior of host deprived or non-deprived females, and observe how the several situations of deprivation (days without host) influence oviposition. Six groups were assembled, three deprived of the host (for 2, 5 and 8 days) and three control groups (with host), each containing one newly-emerged couple (0-24h) of wild Z. subfasciatus, The non-deprived (control) groups received the hosts every day (5 bean seeds Phaseolus vulgaris (Fabaceae)) and the others were deprived for 2, 5 and 8 days, respectively. For each group 12 repetitions were made. Consequently, 12 couples were host deprived during two days, 12 couples were host deprived during five days and 12 couples were host deprived during eight days. When the seeds of the deprived groups were added the experiments started. There was a control group for each deprived group. The experiments and the insects were maintained at constant temperature 29 ± 2ºC and 70-80% relative humidity. At 15 minutes interval, the number of times the females manifested the different categories of behavior was observed (frequency). The behavior categories were: rest inside the box, locomotion, resource exploration (seeds), copulation and oviposition. The deprived females stayed most of the time in contact with the host to carry out oviposition, while the non-deprived (control) females spent most of the time at rest. This was observed in all the deprivation times. The results show that host deprivation influences the oviposition behavior of the studied species and also shows the flexibility in the oviposition strategies that these females present when the environment changes (absence and presence of resources)

Influence of larval and pupal products on the oviposition behavior of Aedes Fluviatilis (Lutz) (Diptera: Culicidae)

Several larval and pupal products of Aedes fluviatilis (Lutz) were tested for their influence on the oviposition behaviour of females of the same species. Significant (alfa = 0,05) atractiveness was shown by: larval water, previously containing 5 to 15 larvae/1,5 ml; larval water, preserved up to 38 days; evaporate and reconstructed larval water extracts up to 2 years after production and water filtered through fresh or dried ground larvae. hexanic larval water extracts and water filtered through fresh or dired ground pupae did not influence oviposition.

Influence of several plant extracts on the oviposition behaviour of Aedes fluviatilis (Lutz) (Diptera: Culicidae) in the laboratory

Whole, ethanolic, hexanic, lyophilized extracts of several plants and anacardic acid tested in respect of their influence on the oviposition behavior of Aedes fluviatilis (Lutz) at 100, 10 and 1 ppm concentrations. Extracts of Allium stivum, Jatropha curcas, Mikania schenkii, Poinciana regia and Spatodea campanulata had a repulsive effect (α=0.05) on females at 100 ppm, those of Anacardium occidentale, Bidens segetum and Caesalpinia peltophoroides were also repelent at 10 ppm. Extracts of Coriandrum sativum (100, 10 and 1 ppm), Chara Zeylanica (10 ppm), Cupressus sempervirens (10 ppm), Foeniculum vulgare (10 ppm) and Spatodea campanulata (1 ppm) were attractive to the females; 13 (52.0%) of the extracts tested, did not influence the oviposition behavior.

The influence of sugars and amino acids on the blood-feeding behaviour, oviposition and longevity of laboratory colony of Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera: Psychodidae, Phlebotominae)

Schneider's Drosophila medium, a complex amino acid rich medium was tested alone and with seven different sugars for some aspects of the biology of Lutzomyia longipalpis. Statistically significant results were obtained when sucrose was used alone, indicating that among the sugars tested, this is still the most suitable and practical one for the maintenance of L. longipalpis colonies. However, the addition of Schneider's medium to a pool of different sugars, was suggested to be related with the acceptance of the first and second blood meals and to longevity, these being, obviously, quite relevant aspects when tansmission experiments are contemplated.

Physical Factors Influencing the Oviposition of Lutzomyia migonei (Diptera: Psychodidae) in Laboratory Conditions

To determine the influence of physical factors on oviposition of Lutzomyia migonei (Diptera: Psychodidae) under laboratory conditions, two sets of experiments were performed. The first test was to determine the influence of the size of pots on oviposition. Gravid flies were placed individually or in groups in different oviposition pots. The number of eggs laid, oviposition time and survival of gravid females were observed. In the second experiment, the influence of irregular surfaces on oviposition was studied. The results suggested that physical space was not an important factor in the oviposition behavior of L. migonei and that the flies showed a preference to oviposit on irregular horizontal surfaces in response to thigmotropic behavior

Oviposition and eclosion periods of Ixodes didelphidis Fonseca and Aragão, 1951 (Acari: Ixodidae) under laboratory conditions

Oviposition and eclosion periods for Ixodes didelphidis were observed under two temperatures (25ºC and 27ºC) and 90-95% humidity. Although there was a significant increase in the eclosion period (p<0.05) and a tendency to increase the oviposition period at 25ºC, there was neither significant differences in the interval (days), until maximum peak of eclosion nor in the number of emerging larvae during the peak nor the total number of emerged larvae. These temperature values are not critical for embryological development of the species. Because at 27ºC and under high humidity the oviposition and eclosion periods are shorter, and the percentage of emerged larvae is higher, we consider this to be the ideal temperature for laboratory studies.

Oviposition Attractancy of Bacterial Culture Filtrates: response of Culex quinquefasciatus

Oviposition attractants could be used for monitoring as well as controlling mosquitoes by attracting them to lay eggs at chosen sites. In the present study, culture filtrates of seven bacterial species were tested for their attractancy against gravid females of Culex quinquefasciatus. When their oviposition active indices (OAI) were studied, the culture filtrates of Bacillus cereus and Pseudomonas fluorescens exhibited oviposition attractancy (OAI = >0.3) at 100 ppm and the OAI were respectively 0.70 and 0.47. Culture filtrates of B. thuringiensis var. israelensis (wild type), B. t. var. israelensis (mutant) and B. sphaericus showed attractancy at 2000 ppm with OAI of respectively 0.71, 0.59 and 0.68. However, the OAI of B. megaterium as well as Azospirillum brasilense was 0.13 (at 2000 ppm), which was less than 0.3 required to be considered them as attractants. When the oviposition attractancy of the bacterial culture filtrates were compared with that of a known oviposition attractant, p-cresol (at 10 ppm), the culture filtrates of B. t. var. israelensis (wild type) and B. cereus were found to be more active than p-cresol, respectively with 64.2 and 54.3% oviposition.