Oviposition Repellency Research Articles

The effects of simulated rainfall on immature population dynamics of Aedes albopictus and female oviposition

Larvae of Aedes albopictus Skuse typically inhabit natural and artificial containers. Since these larval habitats are replenished by rainfall, Ae. albopictus may experience increased loss of immature stages in areas with high levels of rainfall. In this study, we investigated the effects of rainfall and container water level on population density, and oviposition activity of Ae. albopictus. In field and laboratory experiments, we found that rainfall resulted in the flushing of breeding habitats. Excess rain negatively impacted larval and pupal retention, especially in small habitats. When filled with water to overflowing, container habitats were significantly repellent to ovipositing females. Taken together, these data suggest that rainfall triggers population loss of Ae. albopictus and related species through a direct detrimental effect (flushing out) and an indirect effect (ovipositional repellency).

Repellent effect of non-host vegetables and their extracts on <I>Pieris rapae</I> L.

在室内和田间测定了番茄、茴香、荆芥、莴苣、香菜和丝瓜6种非寄主蔬菜对菜粉蝶的驱避作用。室内测定结果表明, 用非寄主蔬菜粗提物处理甘蓝后, 菜粉蝶成虫对甘蓝的选择反应率降低, 尤其是交配雌蝶对荆芥、茴香、番茄和莴苣提取物处理的甘蓝的选择反应率最低, 分别仅为3.67%、4.30%、5.27%和8.26%。在非寄主蔬菜粗提物处理过的甘蓝苗上, 成虫的产卵量明显减少, 其中以番茄、茴香和荆芥粗提物的驱避活性最强, 处理后1 d的非选择性产卵驱避率分别为91.04%、75.54%和71.67%, 选择性产卵驱避率分别为94.64%、79.66%和78.96%。田间试验结果表明, 甘蓝田套种番茄、茴香和荆芥后, 可使田间落卵量分别减少68.80%、62.62%和55.09%, 这3种非寄主蔬菜对菜粉蝶的有效驱避距离分别为4 m、2 m和2 m左右。因此, 可以通过在甘蓝田套种非寄主蔬菜或喷洒其粗提物驱避菜粉蝶, 减少幼虫发生为害。

Electrophysiological, Flight Orientation and Oviposition Responses of Three Species of Mosquito Vectors to Hexadecyl Pentanoate: Residual Oviposition Repellent Activity

Understanding on the chemical ecology of mosquito behavior is of paramount importance in developing control programs employing attractants and repellents. Several workers focused on topical repellents and oviposition attractants of mosquitoes, however, only limited work has been accomplished on mosquito oviposition repellents. The present systematic investigation provides evidence on the effectiveness of a C21 fatty acid ester- hexadecyl pentanoate, to stimulate antennal olfactory receptors of Aedes aegypti (L.), Ae. albopictus (Skuse), and Anopheles stephensi (Liston) that mediate their long-range olfaction guided flight orientation behavior by repelling the gravid females of these mosquito vectors in the olfactometer. The compound loaded onto an effervescent tablet retained its repellent property in the treated substrates for up to 1 wk at 10 mg/L. In places, where the mosquito breeding habitats are near to human habitations, could be treated with hexadecyl pentanoate to repel the ovipositing gravid females as a component of the integrated approach for mosquito management by disrupting the mosquito life cycle and population growth.

Electrophysiological, Flight Orientation and Oviposition Responses of Three Species of Mosquito Vectors to Hexadecyl Pentanoate: Residual Oviposition Repellent Activity

Understanding on the chemical ecology of mosquito behavior is of paramount importance in developing control programs employing attractants and repellents. Several workers focused on topical repellents and oviposition attractants of mosquitoes, however, only limited work has been accomplished on mosquito oviposition repellents. The present systematic investigation provides evidence on the effectiveness of a C21 fatty acid ester- hexadecyl pentanoate, to stimulate antennal olfactory receptors of Aedes aegypti (L.), Ae. albopictus (Skuse), and Anopheles stephensi (Liston) that mediate their long-range olfaction guided flight orientation behavior by repelling the gravid females of these mosquito vectors in the olfactometer. The compound loaded onto an effervescent tablet retained its repellent property in the treated substrates for up to 1 wk at 10 mg/L. In places, where the mosquito breeding habitats are near to human habitations, could be treated with hexadecyl pentanoate to repel the ovipositing gravid females as a component of the integrated approach for mosquito management by disrupting the mosquito life cycle and population growth.

Studies on effects of indigenous plant extracts on filarial vector Culex tritaeniorhynchus Giles

Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The purpose of the present study was to assess the effect of leaf ethyl acetate, acetone and methanol extracts of Aegle marmelos (L.) Correa ex Roxb (Rutaceae), Andrographis lineata Wallich ex Nees. (Acanthaceae), Andrographis paniculata (Burm.f.) Wall. ex Nees. (Acanthaceae), Cocculus hirsutus (L.) Diels (Menispermaceae), Eclipta prostrata L. (Asteraceae) and Tagetes erecta L. (Compositae) on ovicidal and oviposition-deterrent activities against Culex tritaeniorhynchus Giles (Diptera: Culicidae). The percentage of egg hatching in methanol extracts of Andrographis lineata, Cocculus hirsutus and T. erecta were 16, 12 and 16 exerted at 500 ppm, respectively. The percentage of effective oviposition repellency was 97.77 at 500 ppm and the lowest repellency was 42.06 at 31.25 ppm in methanol and acetone extracts of Andrographis lineata and Andrographis paniculata, respectively. The oviposition activity index values revealed that the solvent plant extracts have deterrent effect, and they caused a remarkable negative response resulting in oviposition of very few eggs. These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal ecofriendly approach for the control of the Culex tritaeniorhynchus.

Efficacy of botanical extracts against Japanese encephalitis vector, Culex tritaeniorhynchus

The purpose of the present study was to assess the effect of leaf hexane and chloroform extracts of Aegle marmelos, Andrographis lineata, Andrographis paniculata, Cocculus hirsutus, Eclipta prostrata, and Tagetes erecta on repellent, ovicidal, and oviposition-deterrent activities against Culex tritaeniorhynchus Giles (Diptera: Culicidae). The repellent action of the plant extracts tested varied depending on the plant species, part, solvent used in extraction, and the extract dose. The hexane extract of A. paniculata was more effective in exhibiting the repellent action against the mosquito as compared with A. lineata extract. Complete protections for 150 min were found in hexane extract of A. paniculata at 500 ppm against mosquito bites. Mean percent hatchability of the ovicidal activity was observed 24 h after treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. No hatchability was observed with hexane, and chloroform extracts of A. lineata, A. paniculata, and hexane extract of T. erecta were exerted at 1,000 ppm. The percentage of effective oviposition repellency were 95.90, 94.75, 95.04, 90.58, 87.93, 87.14, 94.82, 95.71, 92.26, 90.58, 83.35, and 78.16 at 500 ppm, and the lowest repellency was 69.93, 53.06, 64.81, 70.06, 51.82, 54.54, 48.31, 66.71, 68.82, 61.85, 34.84, and 39.53 at 31.25 ppm in hexane and chloroform extracts of A. marmelos, A. lineata, A. paniculata, C. hirsutus, E. prostrata, and T. erecta, respectively. The oviposition activity index values revealed that the solvent plant extracts have deterrent effect, and they caused a remarkable negative response resulting in oviposition of very few eggs. These results clearly reveal that the hexane extracts of A. marmelos and A. paniculata served as a potential repellent, ovicidal, and oviposition deterrent against Japanese encephalitis vector, C. tritaeniorhynchus.

Oviposition-deterrent, ovicidal, and repellent activities of indigenous plant extracts against Anopheles subpictus Grassi (Diptera: Culicidae)

Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The leaf acetone, ethyl acetate, and methanol extracts of Aegle marmelos (Linn.) Correa ex Roxb, Andrographis lineata Wallich ex Nees, and Cocculus hirsutus (L.) Diels were tested for oviposition-deterrent, ovicidal, and repellent activities against Anopheles subpictus Grassi (Diptera: Culicidae). The percentage of effective oviposition repellency of 92.60 , 93.04, 95.20, 88.26, 92.80, 94.01, 95.77, 96.93, and 92.54 at 500 ppm and the lowest repellency of 47.14, 58.00, 56.52, 64.93, 71.09, 66.42, 50.62, 57.62, and 65.73 at 31.25 ppm in acetone, ethyl acetate, and methanol extracts of Aegle marmelos, Andrographis lineata, and Cocculus hirsutus, respectively. The oviposition activity index (OAI) value of acetone, ethyl acetate, and methanol extracts of Aegle marmelos, Andrographis lineata, and Cocculus hirsutus at 500 ppm were -0.86, -0.87, -0.90, -0.78, -0.87, -0.86, -0.91, -0.94, and -0.86 respectively. The OAI values revealed that the solvent plant extracts have deterrent effect, and they caused a remarkable negative response resulting in oviposition of very few eggs. Mean percent hatchability of the ovicidal activity was observed 24 h after treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Mortality of 100% with ethyl acetate extract of Aegle marmelos, methanol extracts Aegle marmelos, Andrographis lineata, and Cocculus hirsutus were exerted at 1,000 ppm. The maximum repellent activity was observed at 500 ppm in methanol extracts of Aegle marmelos, Andrographis lineata, and ethyl acetate extract of Cocculus hirsutus, and the mean complete protection time ranged from 90 to 120 min with the different extracts tested. These results suggest that the leaf extracts of Aegle marmelos, Andrographis lineata, and Cocculus hirsutus have the potential to be used as an ideal ecofriendly approach for the control of the Anopheles subpictus. Therefore, this study provides first report on the oviposition, ovicidal, and repellent activities against malaria vector, Anopheles subpictus of plant extracts from Southern India.

Headspace solid-phase microextraction gas chromatography–mass spectrometry analysis of Eupatorium odoratum extract as an oviposition repellent

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) analysis was used to study volatile and semi-volatile compounds emitted by the Eupatorium odoratum ( E. odoratum) extract. Variables of HS-SPME such as the type of SPME fiber, extraction time and temperature, incubation time, desorption time and temperature have been optimized. Optimized conditions were obtained by the use of divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber, 5 min/20 min incubation/extraction time at 65 °C, 5 min desorption time at 260 °C. Using three different polar chromatographic columns to get retention index and mass spectrometry data, 99 volatile and semi-volatile compounds were tentatively identified in the E. odoratum extract. This study has identified the promising source of E. odoratum oviposition repellent.

Larvicidal and oviposition‐altering activity of monoterpenoids, trans‐anithole and rosemary oil to the yellow fever mosquito Aedes aegypti (Diptera: Culicidae)

Aedes aegypti L. is the major vector of dengue fever and dengue hemorrhagic fever. In an effort to find effective tools for control programs to reduce mosquito populations, the authors assessed the acute toxicities of 14 monoterpenoids, trans-anithole and the essential oil of rosemary against different larval stages of Ae. aegypti. The potential for piperonyl butoxide (PBO) to act as a synergist for these compounds to increase larvicidal activity was also examined, and the oviposition response of gravid Ae. aegypti females to substrates containing these compounds was evaluated in behavioral bioassays. Pulegone, thymol, eugenol, trans-anithole, rosemary oil and citronellal showed high larvicidal activity against all larval stages of Ae. aegypti (LC(50) values 10.3-40.8 mg L(-1)). The addition of PBO significantly increased the larvicidal activity of all test compounds (3-250-fold). Eugenol, citronellal, thymol, pulegone, rosemary oil and cymene showed oviposition deterrent and/or repellent activities, while the presence of borneol, camphor and beta-pinene increased the number of eggs laid in test containers. This study quantified the lethal and sublethal effects of several phytochemical compounds against all larval stages of Aedes aegypti, providing information that ultimately may have potential in mosquito control programs through acute toxicity and/or the ability to alter reproductive behaviors.

Oviposition responses of Aedes aegypti and Aedes albopictus to certain fatty acid esters

Laboratory studies were carried out to observe the oviposition responses of Aedes aegypti (L.) and Aedes albopictus (Skuse) to several C21 fatty acid esters. The oviposition activity of these dengue and chikungunya vectors to the long-chain fatty acid esters of C21 length have not been reported earlier. From the multiple choice experiments on oviposition activity in standard mosquito cages, it was observed that compounds hexadecyl pentanoate, tetradecyl heptanoate and tridecyl octanoate presented significant oviposition repellent activity against the two mosquito species, while one compound propyl octadecanoate was found to attract A. aegypti to the treated oviposition substrate at 1- and 10-ppm concentrations. The possible utilization of these esters in integrated vector management is discussed.

Botanicals for Use Against Vegetable Pests and Diseases

ABSTRACT Insect pests, nematodes and plant diseases of vegetables are generally controlled by frequent applications of chemical pesticides with an objective to increase crop productivity and obtain greater profit in conventional farming. With consumers' awareness and perception, vegetables without residue of chemicals are being preferred in local and export markets. For this purpose, plant-derived crude products or formulated pesticides can be eco-friendly, effective and economical for an average producer. Neem (Azadirachta indicaA. Juss.) is being widely used in the form of water extracts of leaves or seeds and neem oil owing to its effects as an oviposition deterrent, sterilant, antifeedant, repellent and pesticide against insects, and as an inhibitor of spore germination and development of pathogens and affecting penetration by nematodes into roots. Other indigenous plants also show potential in pest management. Further research needs to be focused on the synthesis and commercial formulations of botanicals for control of pests and pathogens.

Use of Residue Profile Analysis to Identify Modes of Insecticide Activity Contributing to Control of Plum Curculio in Apples

Residue profile analysis techniques were developed, along with laboratory and field-based bioassays to describe the modes of insecticidal activity responsible for the control of the plum curculio, Conotrachelus nenuphar (Herbst), in apples (Malus spp.). Adult plum curculios were treated in laboratory topical bioassays to determine acute contact activity and lethal time for five insecticides. Azinphosmethyl had the highest levels of toxicity and shortest lethal time values, followed by the neonicotinoids thiacloprid, thiamethoxam, and imidacloprid, whereas indoxacarb had the highest LD50 and LT50 values for topical exposure. Field-based residual activity bioassays assessed adult mortality, and fruit and leaf injury from plum curculio exposed to 4 h, 7 d, and 14 d field-aged residues. All compounds caused significant levels of mortality to plum curculio when adults were exposed to fruit clusters 4 h post-application. Thiacloprid, thiamethoxam, and imidacloprid showed oviposition deterrence, antifeedant, and repellency effects in the 7- and/or 14 d residual bioassays and protected fruit in the absence of significant lethal activity. Indoxacarb maintained lethal activity throughout the study intervals, with the incidence of plum curculio feeding, suggesting that ingestion is an important mode of entry. For the neonicotinoids thiacloprid, thiamethoxam and imidacloprid plum curculio mortality was highly correlated with fruit and leaf surface residues. As surface residues declined, sublethal effects such as oviposition deterrence and antifeedant effect remained. The value of the plant–insect–chemistry triad model for describing the temporal dimensions of insecticidal modes of activity and understanding a compound’s critical performance characteristics is discussed.

Use of Residue Profile Analysis to Identify Modes of Insecticide Activity Contributing to Control of Plum Curculio in Apples

Residue profile analysis techniques were developed, along with laboratory and field-based bioassays to describe the modes of insecticidal activity responsible for the control of the plum curculio, Conotrachelus nenuphar (Herbst), in apples (Malus spp.). Adult plum curculios were treated in laboratory topical bioassays to determine acute contact activity and lethal time for five insecticides. Azinphosmethyl had the highest levels of toxicity and shortest lethal time values, followed by the neonicotinoids thiacloprid, thiamethoxam, and imidacloprid, whereas indoxacarb had the highest LD50 and LT50 values for topical exposure. Field-based residual activity bioassays assessed adult mortality, and fruit and leaf injury from plum curculio exposed to 4 h, 7 d, and 14 d field-aged residues. All compounds caused significant levels of mortality to plum curculio when adults were exposed to fruit clusters 4 h post-application. Thiacloprid, thiamethoxam, and imidacloprid showed oviposition deterrence, antifeedant, and repellency effects in the 7- and/or 14 d residual bioassays and protected fruit in the absence of significant lethal activity. Indoxacarb maintained lethal activity throughout the study intervals, with the incidence of plum curculio feeding, suggesting that ingestion is an important mode of entry. For the neonicotinoids thiacloprid, thiamethoxam and imidacloprid plum curculio mortality was highly correlated with fruit and leaf surface residues. As surface residues declined, sublethal effects such as oviposition deterrence and antifeedant effect remained. The value of the plant-insect-chemistry triad model for describing the temporal dimensions of insecticidal modes of activity and understanding a compound's critical performance characteristics is discussed.

LABORATORY EVALUATION OF 21 INSECT REPELLENTS AS LARVICIDES AND AS OVIPOSITION DETERRENTS OF AEDES ALBOPICTUS (DIPTERA: CULICIDAE)

Twenty-one commercial insect repellent products, including 12 botanical, 6 DEET-based, and 3 synthetic organics, were evaluated as larvicides and as oviposition deterrents of Aedes albopictus. Ten of the 12 botanical products at 0.1% concentration provided 57-100% mortality of laboratory-reared 4th-stage Ae. albopictus larvae at 24 h after treatment. Five of the 6 DEET-based products and 3 synthetic organic repellents at 0.1% concentration induced 88-100% larval mortality at 24 h after treatment. All 12 botanical products proved highly effective oviposition deterrents of Ae. albopictus, resulting in 76-100% effective repellency at 24 h after exposure. The 6 DEET-based repellents and the 3 synthetic organic repellents caused 84-100% effective oviposition repellency of Ae. albopictus at 24 h after exposure. Several botanical repellents previously shown to have minimal protection from mosquito bites proved effective oviposition deterrents. Some commercial topical repellents have good potential for development and use in management of container-inhabiting mosquitoes because they deter oviposition and kill larvae.

VEGETATION-DERIVED CUES FOR THE SELECTION OF OVIPOSITION SUBSTRATES BY ANOPHELES ALBIMANUS UNDER LABORATORY CONDITIONS

Oviposition response of gravid Anopheles albimanus Wiedemman (Diptera: Culicidae) females to water containing Brachiaria mutica, Cynodon dactylon, Jouvea straminea, Fimbristylis spadicea, and Ceratophyllum demersum was investigated. Gravid An. albimanus females deposited similar egg numbers in cups containing natural plants in water from natural breeding sites and in cups containing natural plants in distilled water. Gravid mosquitoes deposited significantly more eggs in cups containing natural plants in water from natural breeding sites than in cups containing artificial plants in water from the corresponding natural breeding sites. These results were confirmed in experiments conducted in a wind tunnel, indicating that female response is mediated by chemical cues from plants. Bioassays with organic extracts of all 5 plant species indicated that these extracts at 100%, 10%, and 1% concentrations had an oviposition repellent effect, while attractiveness was observed at 0.1%, 0.01%, and 0.001%. Gas chromatography and mass spectrometry analysis of the organic extracts found in all 5 plants showed a mixture of terpenoid and alcohol compounds, among them: guaiacol, phenol, isoeugenol, longifolene, caryophyllene, phenyl ethyl alcohol, and p-cresol. These results suggest that middle-range volatiles from plants may function as chemical cues for the female's oviposition response in this mosquito species.

Experience‐induced preference for oviposition repellents derived from a non‐host plant by a specialist herbivore

AbstractForaging adults of phytophagous insects are attracted by host‐plant volatiles and supposedly repelled by volatiles from non‐host plants. In behavioural control of pest insects, chemicals derived from non‐host plants applied to crops are expected to repel searching adults and thereby reduce egg laying. How experience by searching adults of non‐host volatiles affects their subsequent searching and oviposition behaviour has been rarely tested. In laboratory experiments, we examined the effect of experience of a non‐host‐plant extract on the oviposition behaviour of the diamondback moth (DBM), Plutella xylostella, a specialist herbivore of cruciferous plants. Naive ovipositing DBM females were repelled by an extract of dried leaves of Chrysanthemum morifolium, a non‐host plant of DBM, but experienced females were not repelled. Instead they were attracted by host plants treated with the non‐host‐plant extract and laid a higher proportion of eggs on treated than on untreated host plants. Such behavioural changes induced by experience could lead to host‐plant range expansion in phytophagous insects and play an important role in determining outcome for pest management of some behavioural manipulation methods.

Influence of azadirachtin on development and reproduction of Nezara viridula L. (Het., Pentatomidae)

Abstract: The potential of azadirachtin as an insect growth regulator was evaluated in Nezara viridula L. by applying different doses to fifth instar nymphs. At doses of 200–500 ng per insect almost all the individuals died during moulting to adults and the survivors showed a great number of nymphal characteristics, and also died very soon after. At lower doses, from 2 to 50 ng per insect, approximately 50% of the adults seemed normal. No effect was observed during the last nymphal instar, even at the highest dose applied. The fertility and fecundity of adults, males and females, developing from nymphs treated with different low doses of azadirachtin were also studied. When azadirachtin was applied at 20 ng per insect on fifth instar nymphs, females developing from these nymphs showed a conspicuous reduction of fecundity. This same effect was evident when untreated females mated with males obtained from treated nymphs. Finally, azadirachtin applied at 1 μg/cm2 to the oviposition surface showed a remarkable oviposition repellency.

Chemical variation in an Ocimum basilicum germplasm collection and activity of the essential oils on Callosobruchus maculatus

A comparative study of the anti-bruchid activity and chemical composition of the essential oils of a germplasm collection of 18 Ocimum basilicum accessions was undertaken. Some essential oils inhibited the oviposition (repellency) and others caused mortality (toxicity) of the stored pulses pest Callosobruchus maculatus. Methyl chavicol and/or linalool were present in the active oils.

Laboratory Toxicity of Three Mosquito Oviposition Repellents to Six Nontarget Aquatic Invertebrates

Abstract Toxicity of three mosquito oviposition repellents, N,N-diethyl-3-methylbenzamide (AI3-22542 or deet), AI3-35765, and AI3-37220 to 6 aquatic nontarget invertebrates, was evaluated in the laboratory. The 24-h LC50 values for Cypricercus sp. (Ostracoda), Moina sp. (Cladocera), Eucyclops agilis Koch (Copepoda), Strelkovimermis spiculatus Poinar & Camino (Nematoda), first- and fourth-instar Toxorhynchites amboinensis Doleschall larvae (Diptera), and fourth-instar Chironomus decorus Johannsen larvae (Diptera) ranged from 0.012 to 0.127% or 120 to 1,270 ppm. Cypricercus sp., Moina sp., E. agilis, first-instar Tx. amboinensis and fourth-instar C. decorus were generally more sensitive to the test repellents than male and female S. spiculatus and fourth-instar Tx. amboinensis. Male S. spiculatus was more sensitive to the repellents than its female and this was probably because of the smaller body size of the male. All invertebrates were generally more sensitive to AI3-37220 than to deet and AI3-35765. The ...

Oviposition attraction and repellency of Aedes aegypti (Diptera: Culicidae) to waters from conspecific larvae subjected to crowding, confinement, starvation, or infection.

As the biomass of Aedes aegypti (L.) larvae increased in relation to the volume of rearing waters, oviposition attraction of these waters to conspecific, gravid females first rose to a peak and then declined. Further increases in biomass rendered waters strongly repellent. Comparable responses were elicited by a decrease in the volume of rearing waters or an increase in the relative size or number of mosquito larvae. Low volumes of water reduced oviposition attraction and increased repellency, whereas larger volumes increased attraction. Excessively large volumes diluted attraction to neutrality. Constraints imposed by the physical dimensions of the larval environment which interfered with the normal postural movements and behaviors of the larvae also induced repellency, independent of rearing volume. Titration of repellent waters revealed that infection with the digenean Plagiorchis elegans (Rudolphi) generated the most powerful repellent effect, whereas crowding or starvation induced significantly weaker responses. At no time did dilution of repellent waters restore attractive properties. Repellents, even at minute concentrations, overrode attractants. The density-dependent action of oviposition attractants and repellents may help to maintain larval populations near optimal levels through their influence on recruitment. Oviposition repellency induced by sublethal infections with P. elegans may maintain population levels below the carrying capacity of the environment. Persistence of oviposition attraction and repellency varied inversely with temperature. The magnitude of the repellent effect induced by larvae appears to be a good indicator of their probability of survival and may be of selective significance. Repellency may deflect ovipositing females away from sites close to human habitation and may lead to new, and perhaps more effective, method, to control mosquitoes and the diseases they transmit.