Pupal Collections Research Articles

Geographic distribution of deltamethrin resistance in malaria vectors from 2010 to 2020 in Republic of Benin, West Africa

The current study aims to establish the cartography of deltamethrin resistance in malaria vectors from 2010 to 2020 in Republic of Benin. An. gambiae s.l. populations were collected from March to July during the great rainy season in Ouémé in 2010, Littoral in 2012, Atlantic in 2012, Couffo in 2020 and Collines in 2012. An. gambiae s.l. populations were also collected from May to October during the rainy season in Alibori in 2012 and in 2015. Susceptibility tests were done following WHO protocol on unfed females’ mosquitoes aged 2-5 days old reared from larval and pupal collections with papers impregnated with deltamethrin (0.05%). The results showed that the populations of Anopheles gambiae s.l. from Adjara, Dangbo and Missérété were resistant to deltamethrin in 2010 whereas the populations of Anopheles gambiae s.l. from Kandi, Malanville, Cotonou, Allada and Dassa-Zoumè were resistant to this product in 2012. The populations of Anopheles gambiae s.l. from Parakou were resistant to deltamethrin in 2015 whereas the populations of Anopheles gambiae s.l. from Dogbo were resistant to the same product in 2020. The establishment of mapping or geographic distribution of deltamethrin resistance in malaria vectors from 2010 to 2020 in Republic of Benin is useful as this will properly inform control programs of the most suitable insecticides to use and facilitate the design of appropriate future resistance management strategies.

Detection and population genetic analysis of kdr L1014F variant in eastern Ethiopian Anopheles stephensi.

Anopheles stephensi is a malaria vector that has been recently introduced into East Africa, where it threatens to increase malaria disease burden. The use of insecticides, especially pyrethroids, is still one of the primary malaria vector control strategies worldwide. The knockdown resistance (kdr) mutation in the IIS6 transmembrane segment of the voltage-gated sodium channel (vgsc) is one of the main molecular mechanisms of pyrethroid resistance in Anopheles. Extensive pyrethroid resistance in An. stephensi has been previously reported in Ethiopia. Thus, it is important to determine whether or not the kdr mutation is present in An. stephensi populations in Ethiopia to inform vector control strategies. In the present study, the kdr locus was analyzed in An. stephensi collected from ten urban sites (Awash Sebat Kilo, Bati, Dire Dawa, Degehabur, Erer Gota, Godey, Gewane, Jigjiga, Semera, and Kebridehar) situated in Somali, Afar, and Amhara regions, and Dire Dawa Administrative City, to evaluate the frequency and evolution of kdr mutations and the association of the mutation with permethrin resistance phenotypes. Permethrin is one of the pyrethroid insecticides used for vector control in eastern Ethiopia. DNA extractions were performed on adult mosquitoes from CDC light trap collections and those raised from larval and pupal collections. PCR and targeted sequencing were used to analyze the IIS6 transmembrane segment of the vgsc gene. Of 159 An. stephensi specimens analyzed from the population survey, nine (5.7%) carried the kdr mutation (L1014F). An. stephensi with kdr mutations were only observed from Bati, Degehabur, Dire Dawa, Gewane, and Semera. We further selected randomly twenty resistant and twenty susceptible An. stephensi mosquitoes from Dire Dawa post-exposure to permethrin and investigated the role of kdr in pyrethroid resistance by comparing the vgsc gene in the two populations. We found no kdr mutations in the permethrin-resistant mosquitoes. Population genetic analysis of the sequences, including neighboring introns, revealed limited evidence of non-neutral evolution (e.g., selection) at this locus. The low kdr mutation frequency detected and the lack of kdr mutation in the permethrin-resistant mosquitoes suggest the existence of other molecular mechanisms of pyrethroid resistance in eastern Ethiopian An. stephensi.

Residual Activity of Pyriproxyfen Against Mosquitoes in Catch Basins in Northwestern Riverside County, Southern California.

A field study was carried out on the year-long residual activity of the insect growth regulator (IGR) pyriproxyfen (Nylar 0.5G) in comparison with methoprene (Altosid® XRP Pellets) against mosquito developmental stages in catch basins in northwestern Riverside County, southern California. Pyriproxyfen was applied at 75, 100, 125, 150, 175 g per catch basin and methoprene at 3.5 g per catch basin. A total of 80 catch basins (10 per each treatment and 20 for control) were used. Posttreatment observations of catch basins were carried out at weekly intervals, with all pupal collections reared to adults. Mosquito species composition in this study, consisting mostly of Culex species (693), was predominated by Cx. quinquefasciatus (92.8%), followed by Cx. erythrothorax (5.5%), Cx. tarsalis (1.2%), Cx. stigmatosoma (0.3%), and Cx. thriambus (0.2%). Activity of both IGRs was expressed as percent inhibition of adult emergence (% IAE). Data generated on % IAE showed that, like methoprene, pyriproxyfen provided complete control of mosquitoes at 75, 125, and 175 g per catch basin up to 50 wk posttreatment at the Riverside amusement park, whereas its activity against mosquitoes in catch basins treated with 100 g and 150 g at the Eastvale site was short-lived, up to 48 wk. Water samples, bioassayed against laboratory-reared, 4th-stage larvae of Cx. quinquefasciatus 1-2 wk after the 50-wk-long study, showed evidence of significant % IAE (∼50) by pyriproxyfen at the 2 higher rates (125 g, 175 g) used at the amusement park. In conclusion, pyriproxyfen can be used to effectively control mosquitoes in catch basins for 48-50 wk, depending on the rate of application.

Larviciding Culex spp. (Diptera: Culicidae) Populations in Catch Basins and Its Impact on West Nile Virus Transmission in Urban Parks in Atlanta, GA.

In urban environments, road-side catch basins are common larval habitats of Culex spp. (Diptera: Culicidae) mosquitoes and important targets of larval control in areas subject to West Nile virus (WNv) transmission. We quantified the impact of larviciding basins on Culex spp. populations and WNv infection prevalence by treating basins in and around urban parks in Atlanta, GA, using Mosquito Dunks and Bits (active ingredient, a.i., Bacillus thuringiensis subsp. isrealensis, Dunks-10.31%, Bits-2.86%) and Altosid 30-Day Briquets (a.i., S-methoprene 8.62%) in two separate seasons. Treatments were coupled with WNv surveillance using gravid traps and aspiration of adults resting in basins. Larviciding led to >90% reductions in Culex spp. larval and pupal collections (Dunks/Bits) and >90% pupal mortality (Briquets) in treated sites during treatment periods; however, we did not observe significant reductions in Culex spp. collections in gravid traps (general linear mixed-effects model [GLMM] result, P > 0.1) or in adults collected resting in basins (GLMM, P > 0.5). In addition, WNv infection prevalence in Culex spp. mosquitoes was similar between treated and untreated sites (GLMM, P > 0.05). Larval control remains important for controlling WNv in Atlanta; however, at the scale and frequency applied in our study, larval control alone may not lead to meaningful reductions in adult populations and WNv infection prevalence. A greater understanding of the annual dynamics of Culex spp. breeding and the importance of basins as Culex spp. larval habitats are needed to meaningfully affect WNv in cities such as Atlanta.

Seasonal abundance, blood meal sources and insecticide susceptibility in major anopheline malaria vectors from southern Mauritania

Malaria is endemic in the southernmost Sahelian zone of Mauritania where the major known mosquito vector is Anopheles arabiensis. Understanding seasonal population dynamics, feeding preferences and insecticide resistance status of these vectors in the area is essential to improve vector control measures implemented at a local scale. Here, malaria vector populations’ bionomics is described in two sentinel sites located in the Sahelian zone of Mauritania. Between September 2014 and December 2016, longitudinal entomological surveys were conducted in Kobeni (15°49'N, 09°24'W) and Rosso (16°30'N; 15°48'W), two localities in the southern Sahelian zone of Mauritania. Adult mosquitoes were collected using indoor pyrethrum spray catch (PSC). Morphological and PCR-based methods were used to identify the species, detect Plasmodium parasites and analyze blood meals in individual mosquitoes. WHO insecticide susceptibility tests were performed with malathion (5%), bendiocarb (0.1%), permethrin (0.75%) and deltamethrin (0.05%) using female An. gambiae (s.l.) reared from larval and pupal collections from natural breeding sites. A total of 2702 Anopheles mosquitoes were collected by PSC during the study period comprising 2291 Anopheles gambiae (s.l.), 376 Anopheles rufipes and 35 Anopheles pharoensis. In Rosso, all mosquitoes from the An. gambiae (s.l.) complex were molecularly identified as An. arabiensis (n = 455/455, 100%). Anopheles pharoensis represented 2.5% (n = 35/1420) of the specimens collected by PSC in Rosso. In Kobeni, An. arabiensis was dominant (n = 278/301, 92.3%) and occurred together with Anopheles coluzzii (n = 18/301, 6%) and An. gambiae (s.s.) (n = 3/301, 1%). Two An. coluzzii × An. arabiensis hybrids were also detected (0.7%) in Kobeni, and An. rufipes was the only other Anopheles species found resting indoors (n = 376/1277, 29.4%). There was an average of 5.6 and 3.6 indoor resting female An. gambiae (s.l.) per room in Kobeni and Rosso, respectively. Indoor resting female An. gambiae (s.l.) mosquitoes in both sites fed most frequently on bovine blood (35.5% in Rosso and 37% in Kobeni). The proportion of An. gambiae (s.l.) mosquitoes that took human blood was significantly higher in Kobeni (HBI = 37%) than in Rosso (HBI = 5.6%) and 32% of An. gambiae (s.l.) mosquitoes contained blood from more than one host species. None of the 1414 tested mosquitoes in both sites were found positive for Plasmodium spp. sporozoites. WHO insecticide resistance tests revealed resistance to permethrin in the An. arabiensis population from Rosso (mortality = 64%) as well as reduced mortality to deltamethrin (mortality = 97%). This study provides updated information on the composition and dynamics of the malaria vector system in southern Mauritania where malaria is endemic. Such data are a necessary prerequisite to devise and implement tailored malaria elimination strategies in areas of low residual transmission.

The Parasitoids of the Asparagus Miner (Diptera: Agromyzidae): Field Parasitism and the Influence of Food Resources on Life History

The goals of this study were to identify pupal parasitoids of the asparagus miner, Ophiomyia simplex Loew (Diptera: Agromyzidae), and examine the effect of different diets and floral resources on the lifespan of adult asparagus miners and their parasitoids. We also measured the effect of parasitism on stem damage caused by the asparagus miner. The identity and abundance of the parasitoids of the asparagus miner were determined in asparagus fields in Michigan from weekly asparagus miner pupal collections during the 2010-2013 seasons. Twelve species of hymenopterous parasitoids were reared from asparagus miner pupae, including Chorebus rondanii (Giard) (Ichneumonoidea: Braconidae), 10 species in three families of Chalcidoidea, and one species of Bethylidae (Chrysidoidea), that represent new host records for the asparagus miner. C. rondanii and Thinodytes cephalon (Walker) (Pteromalidae) were the most common parasitoids. The effects of different diets and flowers on the lifespan of the pest and parasitoid adults were also evaluated. Buckwheat resulted in the shortest life span for the asparagus miner, whereas Riddell's goldenrod significantly increased its lifespan relative to the control. Parasitoid lifespan was doubled when individuals were fed sugar-rich diets. In the field, parasitoids preferred stems that contained more pupae and damage. The two most commonly reared parasitoids should be considered as targets for future conservation biological control efforts of the asparagus miner.

Blood meal origins and insecticide susceptibility of Anopheles arabiensis from Chano in South-West Ethiopia

BackgroundAnopheles arabiensis, the main malaria vector in Ethiopia, shows both anthropophilic and zoophilic behaviours. Insecticide resistance is increasing, and alternative methods of vector control are needed. The objectives of this study were to determine the blood meal origins and the susceptibility to insecticides of An. arabiensis from Chano village near Arba Minch in South-West Ethiopia.MethodsBlood meal sources of anopheline mosquitoes collected using Centers for Disease Control and Prevention (CDC) light traps and pyrethrum spray catches (PSC) from human dwellings, and hand-held mouth aspirators from outdoor pit shelters were analysed using a direct enzyme-linked-immunosorbent assay (ELISA). The susceptibility of An. arabiensis to pyrethroid insecticides (alphacypermethrin, lambdacyhalothrin, deltamethrin, and cyfluthrin) and DDT was assessed using females reared from larval and pupal collections from natural breeding sites.ResultsThe blood meal origins of 2967 freshly fed Anopheles mosquitoes were determined. An. arabiensis was the predominant species (75%), and it fed mainly on cattle. The densities of both freshly fed An. arabiensis and those fed on human blood followed similar seasonal patterns. The overall human blood index (HBI) of An. arabiensis, including mixed blood meals, was 44% and the bovine blood index (BBI) was 69%. The HBI of An. arabiensis from CDC light trap collections was 75% and this was higher than those for PSC (38%) and outdoor pit shelter collections (13%), while the BBI was 65% for PSC, 68% for outdoor pit shelters and 72% for CDC light traps. More freshly fed and human blood-fed An. arabiensis were sampled from houses close to the shore of Lake Abaya (the major breeding site).A high proportion of An. arabiensis was resistant to the pyrethroid insecticides, with a mortality rate of 56% for lambdacyhalothrin, 50% for cyfluthrin and alphacypermethrin, 47% for deltamethrin, and 10% for DDT.ConclusionAnopheles arabiensis is the predominant species of anopheline mosquito in this region, and cattle are the main source of its blood meals. The greater tendency of this species to feed on cattle justifies the application of insecticides on cattle to control it. However, An. arabiensis has already developed resistance to the available pyrethroid insecticides, and alternative insecticides are needed for malaria vector control.

Productivity and population density estimates of the dengue vector mosquito Aedes aegypti (Stegomyia aegypti) in Australia

New mosquito control strategies centred on the modifying of populations require knowledge of existing population densities at release sites and an understanding of breeding site ecology. Using a quantitative pupal survey method, we investigated production of the dengue vector Aedes aegypti (L.) (Stegomyia aegypti) (Diptera: Culicidae) in Cairns, Queensland, Australia, and found that garden accoutrements represented the most common container type. Deliberately placed 'sentinel' containers were set at seven houses and sampled for pupae over 10 weeks during the wet season. Pupal production was approximately constant; tyres and buckets represented the most productive container types. Sentinel tyres produced the largest female mosquitoes, but were relatively rare in the field survey. We then used field-collected data to make estimates of per premises population density using three different approaches. Estimates of female Ae. aegypti abundance per premises made using the container-inhabiting mosquito simulation (CIMSiM) model [95% confidence interval (CI) 18.5-29.1 females] concorded reasonably well with estimates obtained using a standing crop calculation based on pupal collections (95% CI 8.8-22.5) and using BG-Sentinel traps and a sampling rate correction factor (95% CI 6.2-35.2). By first describing local Ae. aegypti productivity, we were able to compare three separate population density estimates which provided similar results. We anticipate that this will provide researchers and health officials with several tools with which to make estimates of population densities.

Insecticide resistance in Anopheles arabiensis (Diptera: Culicidae) from villages in central, northern and south west Ethiopia and detection of kdr mutation

BackgroundAnopheles arabiensis is the major vector of malaria in Ethiopia. Malaria vector control in Ethiopia is based on selective indoor residual spraying using DDT, distribution of long lasting insecticide treated nets and environmental management of larval breeding habitats. DDT and pyrethroid insecticides are neurotoxins and have a similar mode of action on the sodium ion channel of insects. It was therefore necessary to verify the insecticide susceptibility status of An. arabiensis, to better understand the status of cross-resistance between DDT and the pyrethroids in this species as well as to detect a resistant gene.MethodsStandard WHO insecticide susceptibility tests were conducted on adults reared from larval and pupal collections from breeding sites at three villages namely: Sodere in the Rift Valley, Gorgora in the north and Ghibe River Valley in the south west of Ethiopia. The occurrence of cross-resistance between pyrethroids and DDT was determined using a DDT selected laboratory colony originally collected from Gorgora. Phenotypically characterized mosquitoes were tested for the presence of knockdown resistance (kdr) alleles using the standard polymerase chain reaction assay.ResultsAll An. gambiae s.l. specimens assayed by PCR were identified as An. arabiensis. The knockdown and mortality results showed An. arabiensis resistance to DDT in all villages, resistance to deltamethrin and permethrin in the Ghibe River Valley and permethrin resistance in Gorgora. Bioassay susceptibility tests also indicated the presence of cross-resistance between DDT and permethrin, but not between DDT and deltamethrin. The knockdown resistance (kdr) mutation of leucine to phenylalanine in the sodium ion channel gene was detected in populations from Gorgora and the Ghibe River Valley.ConclusionSince An. arabiensis shows high levels of resistance to DDT in all villages tested and varying pyrethroid resistance in Gorgora and the Ghibe River valley, precautionary measures should be taken in future vector control operations. Moreover, the status of resistance in other locations in Ethiopia and the spread of resistant gene (s) should be investigated.

Relative Abundance of Stable Fly and House Fly (Diptera: Muscidae) Pupal Parasites (Hymenoptera: Pteromalidae; Coleoptera: Staphylinidae) on Confinement Dairies in California

Four dairies in southern California were sampled weekly from April 1987 through June 1988 to determine the distribution and relative abundance of stable fly, Stomoxys calcitrans (L.), and house fly, Musca domestica L., pupal parasites. Seven parasite species represented ≍90% of the parasites recovered from stable fly and house fly pupae, and included Spalangia endius Walker, Spalangia cameroni Perkins, Spalangia nigroaenea Curtis, Muscidifurax raptor Girault and Sanders, Muscidifurax zaraptor Kogan and Legner, Urolepis rufipes (Ashmead), and Aleochara spp. U. rufipes had not been previously recorded to parasitize these hosts in California. Most of the U. rufipes recoveries were between April and June. The relative abundance of parasites recovered from stable flies and house flies on four southern California dairies varied slightly for some species, but the overall rate of parasitism only ranged from 13.4 to 19.9%. A limited number of stable fly and house fly pupal collections from dairies in central California revealed a much lower proportion of S. cameroni and a higher proportion of S. endius , when compared with southern California dairies. The majority of stable fly and house fly pupae sampled at four southern California dairies were associated with pure manure substrates. There was no significant difference between the relative abundance of parasites recovered from stable fly pupae sampled from manure, manure plus hay, or wet-hay substrates. Significantly fewer S. nigroaenea and significantly more M. zaraptor were recovered from house fly pupae developing in brewer's grain when compared with manure, manure plus hay, and wet-hay substrates. In pupal samples which contained both stable flies and house flies, S. cameroni was recovered significantly more often from stable fly pupae. In general, there were no significant differences between stable fly and house fly in parasitism by the seven parasite species.

Survivorship and Age-Specific Fertility of Toxorhynchites Brevipalpis Females (Diptera: Culicidae)

Data on life-table phenomena such as survivorship and fertility schedules, net reproductive rate and oviposition behavior were obtained for Toxorhynchites brevipalpis females. The material for laboratory experiments originated from pupal collections from discarded automobile tires at an automobile dump in a Dar es Salaam (Tanzania) suburb. The survivorship schedule showed that maximum survival of Tx. brevipalpis females was 140 days. Close to 50% of the females survived for 84 days. The survivorship curve for females dying accidentally had the shape of a negative exponential decay. For females dying naturally the curve was negatively skewed, resembling the curves for K strategists. Female fertility changed during the reproductive period from 20 eggs per wk to 4 eggs per wk. The average female fecundity was 233 eggs and the maximum fecundity was 364 eggs. At any time during the reproductive period, more than 50% of the females were laying eggs. The post reproductive period was 4.3 ± 1.6 days.

Spatial distribution of the gypsy moth [Lepidoptera: Lymantriidae] and some of its parasitoids within a forest environment

Aspects of the microhabitat distributions of the gypsy moth,Porthetria dispar (L.) (Lepidoptera: Lymantriidae), and some of its parasitoids were investigated in the field by means of sticky panels and gypsy moth egg masses exposed at different heights in trees, by egg masses exposed within forested and cleared areas, and by gypsy moth pupal collections from different heights in trees.Ooencyrtus kuwanai (Howard)(Hymenoptera: Encyrtidae), Apanteles melanoscelusRatzeburg (Hymenoptera: Braconidae), and gypsy moths were caught most frequently on stickly panels placed in upper portions of trees. In contrast,Apanteles laevicepsAshmead, a parasitoid of cutworms, was most often caught near the forest floor.O. kuwanai attacked equally egg masses exposed at different heights in trees, but parasitized those in a clearing less often than those within the forest prosper.Brachymeria intermedia (Nees) (Hymenoptera: Chalcididae) emerged mostly from pupae collected near the tops of trees and not at all from those collected below 5 m. The results are discussed as they relate to field sampling procedures, behavioral activities of gypsy moth and parasitoid adults, and integrated control possibilities for the gypsy moth.

Key to Adults of Dipterous Parasites of Spruce Budworm, Choristoneura Fumiferana (Clem.) (Lepidoptera: Tortricidae)1

Studies on the natural control of the spruce budworm, Choristoneura fumiferana (Clem.) in British Columbia from 1943 to 1948 emphasized the importance of the complex of dipterous parasites. Sixteen species were reared from larval and pupal collections of the budworm. The key herein developed, provides the important characters for identifying and separating those adults most commonly encountered.