الفهرس 
Introduction
Survey of immature mosquito predatorsOnly 14 pages are availabe for public view
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Abstract
Studies on the evaluation of certain biological agents against mosquito larvae were conducted in Assiut area. Results are summarized as follows:
1. Survey of aquatic predators associated with mosquito larvae:
1.1. In Al-Ghorieb area, Assiut governorate, four species of aquatic beetles, Hypera postica, Rhantus mtfwrafo, Enochorus bicolor and Sternolophus solieri belonged to 3 families and order Coleoptera, two species of aquatic bugs belonged to order Hemiptera and two families (Sigara sp. and Arctocrisa hieroglyhica) and two species of Odonata belonged to two families (Agrion sp. and Cordulia sp.) were recorded. Also, G. affinis was surveyed.
1.2. In Arab El-Madabegh (Assiut governorate) where water contain high organic matter, only – 3 species of aquatic predators belonged to order Coleoptera and Odonata were surveyed (Rhantus mtfwrafo, Agrion sp. and Cordulia sp.).
2. Predation of G. affinis from mosquito larvae:
The predation rate of G. affinis from the 4th instar larvae of culicine mosquito was studied. Results showed that high efficient of both female and male of fish for predation at all sizes tested. The average number of mosquito larvae consumed by one male of fish after 8 hr from offering larvae was 41.37 for fish 1.5 cm long, 47.37 for 2.5 cm and 53.71 for 3-5 cm.
The predation rate of females was higher than male, the average number of mosquito larvae consumed after 8 hr was 44.12 for fish 1.5 cm long, 50.13 for 2.5 cm, and 61.19 for 4 cm long.
3. Factors affecting the predation efficiency of G. affinis on mosquito larvae:
3.1. Light:
For male and females of G. affinis the consumption from 2nd mosquito larvae was significantly higher in light than that at darkness despite the fish length. The number of mosquito larvae consumed increased as the length of male fish increases, and the reverse was noticed with females.
The consumption of both male and female of G. affinis from 4th instar larvae was also higher in light than that at darkness despite the fish size. The number of mosquito larvae consumed was much less than that recorded with 2nd instar larvae. Females were much efficient in predation than males, and the consumption of both males and females increased as the size of fish increases.
3.2. Temperature:
Result of the effect of three constant temperatures (25, 30 and 35°C) on the predation efficiency of G. affinis against 4th instar larvae of culicine mosquito showed that, for both male and female, temperature of 30°C was the most favorable degree for predation despite of fish size.
The fish female was in general more efficient in predating mosquito larvae than males under the three temperatures tested.
3.3. pH:
The predation efficiency of both male and females of G. affinis was affected by pH of water. At pH 4 all fishes died, but at pH 7, 4 and 12 the consumption of mosquito larvae varied significantly. In general, pH 9 showed the most favorable level for predation despite fish sex or size. Female was more efficient in predation than male at pH 7 and 9, and the reverse was noticed with pH 12.
3.4. Salinity:
The salinity level (5, 10 and 15%) affected significantly the rate of predation of G. affinis. All fishes died at salinity level of 15%. However, the predation efficiency of both male and female was significantly higher at salinity level 5% than that at 10% despite fish sex or size. The number of mosquito larvae consumed by female was higher than male at salinity level 5%, but the reverse was observed at salinity level of 10% despite fish size.
3.5. Type of water:
The type of water in which mosquito larvae or fish breed, affect the predation efficiency of G. affinis. For both fish male and females and for all sizes of fish, distilled water showed the highest significant favorable water for predation. In general, female predated much higher number of mosquito larvae than males, regardless of fish size.
3.6. Prey density:
The density of mosquito larvae affected the predation efficiency of G. affinis. Results showed that mosquito larvae density (60 larvae/200 ml water) was the most favorable density for predation by G. affinis despite sex or size. In general, females were more efficient in predation than males despite fish size or prey density.
In conclusion, the predation of G. affinis was much efficient in light, temperature 30°C, pH 9, salinity level of 5%, and density prey (60 larvae/200 ml). These results should be taken in biological control programs of mosquito larvae.
4. Predation efficiency of the aquatic beetle Rhantus mtfwrafo on culicine mosquito larvae:
Against 2nd instar larvae of culicine mosquito, one adult consumed between 15 and 18.33, with an average of 16.2 larvae/day.
For the 4th instar larvae, the range of consumption was between 9.33 and 14.67 with an average of 11.13 larvae/day. The rate of predation from 4th instar larvae was much lower than that from 2nd instar larvae.
5. Toxic effect of spinosad 12% in C. pipiens larvae:
The LC50 values of spinosad tested against 2nd instar larvae of C. pipiens were 0.107 and 0.004 ppm after 24 and 48 h exposure. These values increased when exposure period was 48 h to attain 0.882 and 0.252 ppm, respectively.
The slope values were 0.67 and 0.72 after 24 and 48h. The low values of slope indicate that the strain of mosquito used in the study showed heterogeneity response to spinosad. Against the fourth instar larvae, the LC50 values after 24, 48 and 72 h exposure were 0.220, 0.032 and 0.014 ppm, respectively. The corresponding values for LC90 were 1.502, 1.327 and 0.521 ppm, and the slope values were 0.70, 0.79 and 0.82. Also, low values of slope in the 4th instar larvae treatment confirm the result of 2nd instar larvae that C. pipiens used in this experiment showed heterogeneity response to spinosad. In general, 4th instar larvae were more tolerant than 2nd instar larvae to spinosad, and increasing the exposure period increased the percentages of mortality.
According to the percentages of mortality and LC50 and LC90 values, it might be concluded that spinosad exhibited high efficiency against mosquito larvae, and should be used in the integrated management of immature stages of mosquitoes.
6. Efficiency of G. affinis against mosquito larvae under semi-field condition:
The efficiency of G. affinis against culicine mosquito larvae under semi-field condition was conducted. Data showed that fish at length 2.0 cm reduced the population of larvae by 95% after 5 days of introducing the fish. Fish at length 3 reduced the population density of larvae by 97.4% while fish at 4 cm length completely reduced the population of mosquito larvae.
Results of the present study proved that G. affinis is efficient control agent for mosquito larvae.