Electrophoretic analysis of esterase isozymes in organophosphate-resistant mosquitoes (Culex pipiens)

Esterase isozymes from individual mosquitoes, Culex pipiens, were analyzed by thin layer agar gel electrophoresis. Changes in esterase isozyme patterns during the developmental stages were studied. In most strains, only one band was found in eggs. During larval development many bands were gradually formed, and the most anodal bands were lost upon pupation. These larva-specific esterases may be controlled by three or more co-dominant alleles. In the adult, many bands were present that were probably controlled by at least seven loci. Est-2 may be controlled by co-dominant alleles; a recessive silent allele was also found.Esterase isozyme patterns of organophosphorus insecticide-resistant and susceptible strains were compared. Resistant strains had very active esterase bands but different patterns were found in malathion and temephos-resistant strains. The strong bands presumably hydrolyse the insecticides to which the strains are resistant, or their PO analogues. Their substrate specificity was studied with various esters.     

Chromosomal organization of the amplified esterase B1 gene in organophosphate-resistant Culex pipiens quinquefasciatus Say (Diptera, Culicidae)

In Culex pipiens quinquefasciatus from California, high resistance to organophosphorus insecticides is due to an increased production of the detoxifying esterase B1 resulting from a 250-fold amplification of the structural gene. The chromosomal organization of this amplified gene was studied by in situ hybridization techniques. Esterase B1 gene copies were found to be clustered on a single chromosome, tentatively identified as chromosome II.     

Electronic mosquito repellers induce increased biting rates in Aedes aegypti mosquitoes (Diptera: Culicidae)

Studies have demonstrated that electronic mosquito repellers are useless and that some of them could even increase the attraction of mosquitoes. While testing some electronic repellers, we noted that they also promoted an increase in biting rates. The present work has evaluated three commercial devices and a computer program working on five different sound frequencies. In a test chamber, the number of Aedes aegypti L. bite attempts was computed during four cycles of 3 min each by alternately turning the devices off and on. The mosquito biting rates for five sound frequencies (ranging from 9.6 kHz to 18.2 kHz) initially demonstrated a significant increase (ranging from around 20% to 50%), which decreased from 8.3% to 25.1% when the repellers were turned off. The biting rate significantly increased at 11.8 kHz (33.7%) when the device was turned on again. The danger of using electronic repellers and the role of sound frequencies stimulating mosquito biting are discussed.     

Boric acid bait kills adult mosquitoes (Diptera: Culicidae)

The toxicity of boric acid solutions to adult Anopheles quadrimaculatus Say, Culex nigripalpus Theobald, and Aedes albopictus Skuse was evaluated in the laboratory. Median lethal concentrations (LC50 in %) at 24-h exposure for male and female An. quadrimaculatus were 0.317 and 0.885, respectively; for Cx. nigripalpus, 0.273 and 0.560, respectively; and for Ae. albopictus, 0.174 and 0.527, respectively. The LC50 values at 48-h exposure for male and female An. quadrimaculatus were 0.101 and 0.395, respectively; for Cx. nigripalpus, 0.098 and 0.255, respectively; and for Ae. albopictus, 0.078 and 0.244, respectively. In laboratory tests, access for 48 h to sucrose (10%) water containing 1% boric acid (boric acid bait) resulted in 98% mortality in blood fed, gravid, and parous Ae. albopictus. When offered a choice between boric acid bait and sucrose water, 52% of male and 33% of female Ae. albopictus ingested sufficient boric acid bait in 24 h to cause death; after 48 h, respective percent mortalities were 88 and 58%. In outdoor tests, in a walk-in screened cage (156 m3) containing 1,250 female Ae. albopictus, mosquito biting rates on the exposed forearm of a human subject in 3-min exposure were reduced > or = 78% for the boric acid bait treatment, compared with a sucrose water control.     

The mosquitoes (Diptera: Culicidae) of Tabasco,Mexico

To document and update the mosquito species of Tabasco, Mexico, field collection trips were conducted in the two physiographic regions of Tabasco: the coastal plain of the southern gulf and the mountains of Chiapas and Guatemala. Mosquitoes were collected as immature and adult stages during the dry and rainy seasons from 2014 through 2015. Additionally, the Reference Collection of Arthropods of Medical Importance (CAIM‐InDRE) containing mosquitoes of Tabasco was re‐examined. In total, 4,913 specimens were collected and examined, which are divided into seven tribes, 18 genera, 27 subgenera, and 104 species. Of these, one genus (Shannoniana Lane and Cerqueira), two subgenera (Georgecraigius Reinert, Harbach and Kitching, and Carrollia Lutz), and 21 species are new records for the mosquito fauna of Tabasco. Culex metempsytus Dyar is a new record for Mexico and Wyeomyia jocosa (Dyar and Knab) is removed from the Mexican mosquito fauna. Seventeen species historically reported were not found in the field collections conducted here. Taxonomic notes, new distribution limits, and comments about the medical importance of species of mosquitoes of Tabasco are discussed. Tabasco is the second state in Mexico with the largest mosquito richness (104 species), followed by Veracruz with 139 species.     

Molecular identification of mosquitoes (Diptera: Culicidae) in southeastern Australia

DNA barcoding is a modern species identification technique that can be used to distinguish morphologically similar species, and is particularly useful when using small amounts of starting material from partial specimens or from immature stages. In order to use DNA barcoding in a surveillance program, a database containing mosquito barcode sequences is required. This study obtained Cytochrome Oxidase I (COI) sequences for 113 morphologically identified specimens, representing 29 species, six tribes and 12 genera; 17 of these species have not been previously barcoded. Three of the 29 species ─ Culex palpalis, Macleaya macmillani, and an unknown species originally identified as Tripteroides atripes ─ were initially misidentified as they are difficult to separate morphologically, highlighting the utility of DNA barcoding. While most species grouped separately (reciprocally monophyletic), the Cx. pipiens subgroup could not be genetically separated using COI. The average conspecific and congeneric p‐distance was 0.8% and 7.6%, respectively. In our study, we also demonstrate the utility of DNA barcoding in distinguishing exotics from endemic mosquitoes by identifying a single intercepted Stegomyia aegypti egg at an international airport. The use of DNA barcoding dramatically reduced the identification time required compared with rearing specimens through to adults, thereby demonstrating the value of this technique in biosecurity surveillance. The DNA barcodes produced by this study have been uploaded to the ‘Mosquitoes of Australia–Victoria’ project on the Barcode of Life Database (BOLD), which will serve as a resource for the Victorian Arbovirus Disease Control Program and other national and international mosquito surveillance programs.     

Global diversity of mosquitoes (Insecta: Diptera: Culicidae) in freshwater

Mosquitoes that inhabit freshwater habitats play an important role in the ecological food chain, and many of them are vicious biters and transmitters of human and animal diseases. Relevant information about mosquitoes from various regions of the world are noted, including their morphology, taxonomy, habitats, species diversity, distribution, endemicity, phylogeny, and medical importance. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Checklist of Iranian mosquitoes (Diptera: Culicidae).

The mosquito fauna of Iran includes seven genera, 64 species, and three subspecies. The records of 12 other species should be verified. There are 24 species in the most recent checklist of Iranian Anopheles. Two species, An. peditaeniatus and An. fluviatilis species V, have been reported since. An. atroparvus, An. labranchiae, and An. martinius of the Maculipennis Group, and An. cinereus, An. nigerrimus, and An. rhodesiensis rupicola were recorded previously but are not included in the checklist. The checklist of Iranian Culicinae includes ten species of the tribe Aedini, but there are some records of four other species: Aedes aegypti, Ochlerotatus berlandi, Oc. chelli, and Oc. dorsalis. The genus Culex includes 19 species, excluding Cx. impudicus, which has not been collected recently, and some doubtful records of Cx. univittatus, Cx. vishnui, and Cx. vagans. The genus Culiseta includes five species and the genera Coquillettidia and Uranotaenia each include one species in Iran. No information is available for the An. subpictus, Oc. caspius, Oc. detritus, and Oc. pulcritaris species complexes in Iran. The An. claviger and Cx. pipiens complexes and the An. hyrcanus group require review.     

Updated checklist of the mosquitoes (Diptera: Culicidae) of Croatia

Improvement of morphological and molecular identification methods allows the detection of new species of mosquitoes. The mosquito fauna of Croatia currently includes 52 species, belonging to eight genera, including Anopheles (12 species), Aedes (24 species), Coquillettidia (one species), Culex (seven species), Culiseta (six species), Orthopodomyia (one species), and Uranotaenia (one species). This is an updated checklist, which includes five new species found in Croatian mosquito fauna. Two of these are invasive mosquito species, Aedes albopictus (Skuse, 1895) and Aedes japonicus (Theobald 1901), which are spreading across Europe and Croatia. The other three species, Culex laticinctus (Edwards 1913), Culex torrentium (Martini 1925), and Anopheles daciae (Linton, Nicolescu & Harbach 2004) are autochthonous species which haven't been recorded so far. Since there are several more invasive species spreading across Europe, we assume that this is not the final list.     

Updated checklist of the mosquitoes (Diptera: Culicidae) of Belgium

Most information about the systematics and bioecology of Belgian mosquitoes dates back from before 1950, and only scattered information was produced during the last decades. In this paper we review and update the list of mosquito species recorded in Belgium, from first report (1908) to 2015. Six genera and 31 species were recorded so far, including 28 autochthonous species and three invasive alien species recently recorded in Belgium: Aedes albopictus (Skuse 1894), Ae. japonicus japonicus (Theobald 1901), and Ae. koreicus (Edwards 1917). The six genera are Anopheles (five species), Aedes (sixteen species), Coquillettidia (one species), Culex (four species), Culiseta (four species), and Orthopodomyia (one species).     

The mosquitoes (Diptera: Culicidae) in Maliuc (Danube delta)--faunistical and ecological data

The paper reports the results of the survey of the mosquito fauna in the Maliuc area (Danube delta) in 1983-1985. 16 mosquito species have been recorded in the area during the investigations: Anopheles maculipennis--complex, An. hyrcanus, Uranotaenia unguiculata, Coquillettidia richiardii, Culiseta annulata, Aedes vexans, Ae. cinereus, Ae. caspius, Ae. dorsalis, Ae. excrucians, Ae. flavescens, Ae. leucomelas, Ae. intrudens, Culex pipiens, C. martinii, Cx. modestus. They have been captured by light traps, on human bait, with entomological hand net and within an indoor resting site (building). Six types of habitats of adult mosquitoes, taking into account the characteristics of the soil and vegetation have been identified in the area. The quantitative and qualitative differences of the mosquito fauna within these six habitats have been recorded. Also, the suitable capture methods within every habitat have been established.     

An annotated list of the mosquitoes (Diptera: Culicidae) of Mississippi

There has been no previous systematic statewide study of mosquitoes in Mississippi. This survey, resulting in the collection of over 400,000 specimens, was conducted by the authors from 2003 to 2007 throughout much of the state using CO₂‐baited CDC light traps and larval dipping. In addition, a health department contract mosquito surveillance technician collected several thousand specimens from the state from 2001 to 2003. Lastly, specimens housed at the Mississippi State University Entomological Museum, obtained from previous surveys, were included as vouchers for species occurring in the state. The collection records and literature show 60 species as occurring or having occurred in Mississippi. Voucher specimens representing 57 of the 60 species discussed are deposited in the Mississippi Entomological Museum or in the U.S. National Museum of Natural History (USNM), Washington, D.C.     

Gynandromorphs in mosquitoes (Diptera: Culicidae) from Valle del Cauca, Colombia

Gynandromorphs of Culex nigripalpus Theobald (2), Cx. pedroi Sirivanakarn and Belkin (1) and Aedes albopictus (Skuse) (2) are described. Two individuals of the latter species were reared in the laboratory, while the remaining three specimens were wild-caught with different traps in rural areas in Valle del Cauca department, southwestern Colombia. All of the individuals were mounted on microscopic slides with Canada balsam. From each mosquito, main morphological characteristics are described and illustrated. Due to the paucity of information about this subject, these findings as well as other relevant cases are discussed.     

Tires as larval habitats for mosquitoes (Diptera: Culicidae) in southern Manitoba, Canada

In 2003, a survey at waste management grounds and tire dealerships was conducted to determine the species composition of mosquitoes in tires in southern Manitoba, Canada. Over 25% of the 1,142 tires sampled contained a total of 32,474 mosquito larvae and pupae. Culex restuans made up at least 95% of the larvae collected for each month of the summer. Culiseta inornata and Culex tarsalis reached their greatest numbers in July and August, respectively, though they were never abundant. Ochlerotatus triseriatus was also found but never reached more than 1% of the total larvae collected in any given month. Mosquito prevalence was more than three times greater in August (36.1%) than in June (11.7%). Orientation affected prevalence of mosquitoes in tires: 31.4% of vertical tires (tires standing on their treads) contained mosquitoes, whereas mosquitoes were found in only 18.9% of horizontal tires (tires parallel to the ground). Tires in the eastern region of Manitoba contained mosquitoes more often (61.7%), irrespective of date, than Winnipeg (25.9%), the central region (29.1%), or the western region (19.8%). Mosquito prevalence was similar across three size categories of tires, car tires (18.8%), truck tires (19.8%), and semi-trailer tires (26.7%), though tractor tires (47.8%) contained significantly more mosquitoes than tires in the other categories.     

Comparative morphology of the pyloric armature of adult mosquitoes (Diptera: Culicidae)

The structure of the pyloric armature, hypothesized to aid in blood-meal digestion or parasite resistance, was compared quantitatively among the following 8 species in 5 genera of adult mosquitoes from the southeastern United States: Aedes albopictus, Aedes japonicus, Aedes triseriatus, Anopheles punctipennis, Culex pipiens s.l., Culex restuans, Orthopodomyia signifera, and Toxorhynchites rutilus. Females differed significantly among species in the structure of spines composing the armature, with Aedes spp. forming one general group, Culex spp. another, and An. punctipennis and Or. signifera a third. Relationships of species based on structural characters of the armature were consistent with recent culicid phylogenies. Although pyloric armature has been noted in mosquitoes and other insects, this is the first quantitative investigation of the mosquito pyloric armature.     

An annotated checklist of the Anopheles mosquitoes (Diptera: Culicidae) in Iran.

An annotated checklist of the Anopheles mosquitoes in Iran is provided. The list is based on data contained in Iranian manuals and reports and information published elsewhere. Supplementary information is provided for 24 species.     

Feeding patterns of mosquitoes (Diptera: Culicidae) in six Brazilian environmental preservation areas

Feeding patterns of mosquitoes in six Brazilian environmental preservation areas were analyzed by the precipitin technique. The mosquito populations were captured using Shannon traps during different time periods. Bird, cow, dog, horse, opossum, human, and rodent antisera diagnostic tests were employed and results were analyzed by calculating the Sørensen similarity index and using the null‐model test. Of the 647 analyzed specimens, 443 reacted to the utilized antisera, of which 331 reacted to one blood source, with the most frequent being birds (49.4%); and 112 specimens reacted to two blood sources, with the most frequent combination from birds + rodents (14.3%). The feed profiles demonstrated that Anopheles albitarsis, An. evansae, Aedes fulvus, Psorophora albigenu, Ps. albipes, Ps. ferox, and Mansonia titillans fed predominantly on birds. The similarity index showed that in some localities An. cruzii, Chagasia fajardi, Ae. scapularis, Ae. serratus, Haemagogus leucocelaenus, Ps. albigenu, and Ps. ferox presented similar dietary habits. The null‐models test indicated that species from SMSP, INP, CGNP, and THP demonstrated an aggregate pattern, while species from SONP and SBNP showed a random pattern. The mosquitoes fed predominantly on birds, but from an epidemiological standpoint, the eclectic feeding habits were found to be constant among the mosquitoes analyzed.