Humberto Quiroz-Martínez

Oviposition habitat selection for a predator refuge and food source in a mosquito

Abstract.  1. The influence of filamentous algae on oviposition habitat selection by the mosquito Anopheles pseudopunctipennis and the consequences of oviposition decisions on the diet, development, body size, and survival of offspring were examined.

Aquatic insects as predators of mosquito larvae

The appropriate use of mosquito control methods is the only means by which diseases transmitted by these insects can be prevented or controlled (WHO 1982). Since the middle of the 20th century, the primary strategies employed to combat these insects have involved the use of pesticides. After the appearance of DDT in the 1940s and after World War II, control was carried out with insecticides mainly of chlorinated or organophosphate origin (Quiroz et al. 2000b). This modality was used up to the 1990s in Latin American and other developing countries where control campaigns were based on the application of chemical products with larvicidal and/or adulticidal action. However, due to various criticisms and restrictions imposed on the use of pesticides, it has become increasingly necessary to seek more environmentally friendly alternatives for mosquito control. In the search for alternatives in the fight against mosquitoes, biological control could provide ecologically acceptable reductions if suitable biocontrol agents become available. This option could help to resolve problems caused by hematophagous mosquitoes, albeit with some difficulty (WHO 1991). In addition, biological control can be included in an integrated pest management (IPM) program in its classical form through the introduction of entomophagous insects or by the cultivation and maintenance of these natural enemies. Before the 1940s, control actions had been directed specifically at the aquatic ecosystem. The focus was on eliminating larvae, and there was a growing interest in applying biological strategies to reduce mosquito populations at the breeding sites. Researchers were concerned with identifying and evaluating the regulating capabilities of many aquatic predator organisms throughout the world. In the 1920s and 1930s, there appeared a series of studies of various biocontrol agents including the insectivorous aquatic plant Utricularia vulgaris as a predator of mosquito larvae. Various organisms were considered as effective predators of mosquitoes. Among them were mosquito fish Gambusia affinis, and invertebrates such as hydras, insects like Muscidus scatophahgoides and Lispa ulginosa, various unidentified species of aquatic hemipterans, and the predaceous diving beetle Eretes dytiscus. Another important predator complex was the mosquito genus Megarhinus, one of the biological control agents most studied worldwide and now known as Toxorhynchites, including the species M. inornatus and M. splendens. Historic records even include bats for control of adult mosquitoes. In the 1930s some studies were conducted with the aim of quantifying the potential of aquatic predators of mosquito larvae, but there was not always adequate identification of either the predator or the prey. These studies reported the number of larvae consumed as well as the quantity of adults that emerged. Clarke (1938) cited several of those laboratory studies; for example, of a total of 1800 larvae exposed to the insectivorous aquatic plant U. vulgaris, only 3 adults emerged. The backswimmer Notonecta undulate was shown to prey on 4000 larvae in 2 days. When the water scavenger beetle Hydrophilus triangularis and the predaceous diving beetle Dytiscus hybridus were exposed to 3500 larvae, only 20 adults emerged. Another arthropod, the whirligig beetle Dineutus assimilis, consumed 300 Anopheles larvae in 2 days. A combination of Dineutus, Notonecta, and dragonfly nymphs presented with 7500 mosquito larvae allowed the emergence of only 12 adults (Clarke 1938). Worldwide there existed a special interest in applying biological control to mosquitoes, to the extent that the New Jersey Mosquito Extermination Association in 1939 invited two special guests to its annual meeting, Dr. J. L. King (King 1939), a specialist in strategic control in agriculture, and Dr. R. D. Glasgow (Glasgow 1939) who was particularly experienced in this field, to highlight current activities. At that time, there was a search for natural enemies of mosquito eggs, as well as an interest in using bats and birds to combat these vectors. In 1939 the insecticidal properties of dichloro, diphenyl, trichloroethane (DDT) were discovered. 1 Laboratorio de Entomologia, Facultad de Ciencias Biologicas, Universidad Autonoma de Nuevo Leon. 2 Apartado Postal 105 – F, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon, CP 66450, Mexico. Copyright E 2007 by The American Mosquito Control Association, Inc.

Population control of the malaria vector Anopheles pseudopunctipennis by habitat manipulation

Insect vector–borne diseases continue to present a major challenge to human health. Understanding the factors that regulate the size of mosquito populations is considered fundamental to the ability to predict disease transmission rates and for vector population control. The mosquito, Anopheles pseudopunctipennis, a vector of Plasmodium spp., breeds in riverside pools containing filamentous algae in Mesoamerica. Breeding pools along 3 km sections of the River Coatán, Chiapas, Mexico were subjected to algal extraction or left as controls in a cross-over trial extending over 2 years. Initial densities of An. pseudopunctipennis larvae were directly proportional to the prevalence of filamentous algae in each breeding site. The extraction of algae brought about a striking decline in the density of An. pseudopunctipennis larvae sustained for about six weeks, and a concurrent reduction in the adult population in both years of the study. Mark–release experiments indicated that dispersal from adjacent untreated areas was unlikely to exert an important influence on the magnitude of mosquito control that we observed. Habitat manipulation by extraction of filamentous algae offers a unique opportunity for sustainable control of this malaria vector. This technique may represent a valuable intervention, complimenting insecticide spraying of households, to minimize Plasmodium transmission rates in Mesoamerica.

Effectiveness of Spinosad and Temephos for the Control of Mosquito Larvae At A Tire Dump In Allende, Nuevo Leon, Mexico

Abstract The effectiveness of spinosad and temephos for the control of mosquito larvae was evaluated in a tire dump in Allende, Nuevo Leon, Mexico. Three groups of 12 to 17 tires located in tree shade were utilized for this study. After the larvicides were applied, samples were collected weekly from 7 randomly chosen tires. The data showed a significant difference between the larvicides and control. Under the conditions of the present study, the effectiveness of spinosad against mosquito larvae was similar to that of temephos, both being effective for up to 91 days postapplication. In addition, spinosad allowed the establishment of the mosquito predator Toxorhynchites sp.

Diversity, Abundance, and Disturbance Response of Odonata Associated with Breeding Sites of Anopheles pseudopunctipennis (Diptera: Culicidae) in Southern Mexico

Abstract Odonate nymphs are important predators of the immature aquatic stages of mosquitoes. Populations of the malaria vector Anopheles pseudopunctipennis Theobald (Diptera: Culicidae) can be efficiently reduced by extraction of filamentous algae from river pools in southern Mexico. Here, we examined the influence of this intervention on the diversity of odonates associated with mosquito breeding pools after annual extractions of algae from river pools in a 3-km section of the Coatán River, over a period of 2 yr. Odonate sampling was performed at monthly intervals in control and treated sections of the river for 4–5 mo after extraction in both years and before extraction in 1 yr. In total, 16 species, 10 genera, and 6 families of odonates were collected. Shannon diversity index values declined significantly during a period of 1 mo in 2001 and >5 mo in 2002. However, the abundance of odonates captured was not affected by algal extraction. In contrast, year-to-year variation in the diversity and abundance of the odonate community was strongly influenced by precipitation and river volume. Despite the importance of algae in river ecology, we conclude that the mosquito control intervention resulted in minimal impact on the odonate community in southern Mexico.

Selection of oviposition sites by female Aedes aegypti exposed to two larvicides.

Abstract The selection of oviposition sites by female mosquitoes involves the ability to choose less dangerous larval habitats. The aim of the present study was to evaluate the ovipositional behavior of female Aedes aegypti in selecting sites treated with 2 different larvicides. The study was conducted in metal cages with plastic cups containing paper strips and either spinosad or temephos, or dechlorinated water (control). After exposing all treated and control cups to ovipositing female mosquitoes for 3 days, the paper strips were removed and examined for egg laying. Based on the number of eggs laid per treatment, the oviposition index was found positive for spinosad (0.66) but negative for temephos (−0.49), indicating that the natural product spinosad acted as an attractant and temephos as a repellent.

Impact of environmental manipulation for Anopheles pseudopunctipennis Theobald control on aquatic insect communities in southern Mexico

ABSTRACT Extraction of filamentous algae from river pools is highly effective for the control of Anopheles pseudopunctipennis in southern Mexico. We determined the magnitude of changes to the aquatic insect community following single annual perturbations performed over two years. In 2001, algae were manually removed from all the pools in a 3 km long section of the River Coatán, Mexico, while an adjacent section was left as an untreated control. In 2002, the treatments of both zones were switched and algal extraction was repeated. The abundance of An. pseudopunctipennis larvae + pupae was dramatically reduced by this treatment and remained depressed for two to three months. A total of 11,922 aquatic insects from ten orders, 40 families, and 95 genera were collected in monthly samples taken over five months of each year. Algal extraction did not reduce the overall abundance of aquatic insects in river pools, but a greater abundance and a greater richness of taxa were observed in 2002 compared to the previous year. This was associated with reduced precipitation and river discharge in 2002 compared to 2001. Shannon diversity index values were significantly depressed following algal extraction for a period of three months, in both years, before returning to values similar to those of the control zone. However, differences between years were greater than differences between treatments within a particular year. When insects were classified by functional feeding group (FFG), no significant differences were detected in FFG densities between extraction and control zones over time in either year of the study. Similarly, percent model affinity index values were classified as “not impacted” by the extraction process. Discriminant function analysis identified two orders of insects (Diptera and Odonata), water temperature, dissolved oxygen and conductivity, and river volume (depth, width, and discharge) as being of significant value in defining control and treatment groups in both years. We conclude that habitat manipulation represents an effective and environmentally benign strategy for control of An. pseduopunctipennis. Variation in precipitation and river discharge between years was much more important in determining aquatic insect community composition than variation generated by the filamentous algal extraction treatment.

Predatory capacity and prey selectivity of nymphs of the dragonfly Pantala hymenaea

ABSTRACT Predatory capacity and prey selectivity of nymphs of the dragonfly Pantala hymenaea (Odonata: Libellulidae) were evaluated on larvae of the mosquito Culex quinquefasciatus (Diptera: Culicidae) and larvae of the midge Chironomus plumosus (Diptera: Chironomidae) as prey. With functional response methodology, 7 larval densities were exposed to predator individuals in a glass jar under laboratory conditions. The study was performed in 2 experiments. The 1st was a test system with each prey species alone. The 2nd tested a mixture of both prey species in a 1:1 ratio. Prey selectivity and prey capacity were significantly greater on midge larvae than on mosquito larvae.

MASS REARING AND EGG RELEASE OF BUENOA SCIMITRA BARE AS BIOCONTROL OF LARVAL CULEX QUINQUEFASCIATUS

ABSTRACT Backswimmers have been recognized as the most promising predators of mosquito larvae. The aim of this investigation was to study mass rearing and egg release of Buenoa scimitra for the biological control of Culex quinquefasciatus Say. Among the most important results were that production of backswimmer eggs occurred for 263 days, and also that eggs were released in artificial containers with production of new individuals until the adult stage was obtained. In addition, a statistically significant reduction in mosquito larval density was observed on some sampling dates.

FLEAS (SIPHONAPTERA) AND TICKS (ARACHNIDA: ACARI: IXODIDA) PARASITIZING SMALL MAMMALS IN THE SIERRA SAN ANTONIO PEÑA NEVADA, STATE OF NUEVO LEÓN, MEXICO

ABSTRACT The region of the Sierra San Antonio Peña Nevada is considered a priority terrestrial area for conservation. Studies of its flora and fauna are scarce, especially with regard to host-parasite relationships. The aim of this study was to determine the host-parasite relationship between small mammals and fleas and ticks, because of the lack of taxonomic studies of this relationship. Small mammals were collected with Sherman type traps during a period since February 2000 to December 2002. These animals were anesthetized with chloroform and then ectoparasites were separated. A total of nine species of small mammals were collected Liomys irroratus, Neotoma goldmani, Neotoma mexicana, Peromyscus boylii, Peromyscus maniculatus, Microtus mexicanus; Mustela frenata; Cratogeomys castanops, and Thomomys umbrinus; on which six species of ectoparasites were found, corresponding Dermacentor albipictus, Ixodes sp., Argas sp., Hoplopsyllus affinis, Stenoponia americana and Nosopsyllus fasciatus. The present is the first study in SSAPN about the host-parasite relationship.