Crabs are found in the aquatic ecosystem. Aquatic ecosystem is two types: Fresh water ecosystem and Marine water ecosystem. We investigated the biology of the freshwater crab. Freshwater crabs are included in the aquaculture.
The freshwater crab belongs to the class: Crustacea, Subclass: Malacosreaca, Superorder: Eucarida, Section: Brachyura, Family: Potamidae (Potaminidae) (Kaestner, 1970). According to Kaestner (1970), the family Potamidae (Potamonidae); freshwater crabs include numerous species in subtropical and tropical areas. The family is now often split into the potamidae, Pseudothalpusidae and Trichodactylidae. The land crabs are belonged to four families such as Potamidae, Grapsidae, Gearcinidae and Pinnetheridae.
There are more than 4500 species of crabs. This is the largest and most specialized group. More than 600 species of freshwater crabs are known (Ng, 1998).
A research survey was conducted in the Rajshahi University Campus during the November, 2008 to May, 2009 to explore the faunal diversity of insects. Sweeping net, plastic containers, stretching board, insect pins, alcohol etc. were used for collecting, killing, stretching and preserving the insects. Altogether 500 insect specimens were collected in five months (November 2008, January 2009, February 2009, March 2009 and May 2009) under 12 Orders viz. Orthoptera, Coleoptera, Lepidoptera, Diptera, Hemiptera, Hymenoptera, Odonata, Ephemeroptera, Psocoptera, Isoptera, Mantoidea. Some undetermined orders were also found during the collection period. Order Diptera was found as most abundant (22.2±1.91) followed by the Coleoptera (17.22±4.55). Minimum abundance was recorded for Mantoidea (0.017±0.016) followed by Psocoptera (0.056±0.054). Among three different trapping spots, highest population of insect was trapped in second science building (6.53±2.94) and lowest population was in third science building (5.72±2.03) during November 2008 to May 2009. Highest number of insects was found in November 2008 (12.06±1.33) followed by February 2009 (5.17±1.19). The lowest population of insect was found in January 2009 (4.04±0.12). Collected specimens were preserved in the departmental insectarium’s.
It was monitored for the foraging activity of A. mellifera commenced its foraging activity earlier in the morning. Then in the noon the foraging activity is comparatively low than the morning. Again in afternoon the foraging activity increase than the noon but comparatively low than the morning. At the end of the day the forage rate comparatively minimum in a day. The effect of various climatic conditions was also examined during the study period. Climatic conditions strongly affect the foraging activity of pollinating insects. In my study time a storm night had been occurred. After that night the forage rate of bees significantly change. Because of lack of nectar. Little or no flight activity occurs at or below 10°C (50 F). On clear and sunny days some flight was seen at temperatures of 12-15°C (53.6- 59 F). Flight begins in earnest at 16°C (60.8 F) and the numbers of bees taking foraging trips increases as the temperature continues to rise. Above 20°C (68 F) it tends to reach a relatively constant high level. At low temperatures (below 20-220C), wind, rain and low light intensity reduce the flight activity of bees. At low temperatures fewer bees are observed and most bees forage nearby to the hives (out to a distance of 50 meters), (Morgan et al., 2002).The wind speed should be less than 15 mph. Relative humidity has less effect on the flight activities of Apis mellifera species. However, combination of temperature and humidity is most important in the ripening of the anthers of the flowers and the availability of pollen to visiting insects. Therefore low temperatures and high humidity have the double effect of reducing bee activity and slowing the release of pollen
Foraging behave of Apis melliferawas observed in different hours of the day on one square metre when the bee kept on foraging on litchi trees bloomed with flowers. This experiment was carried out at a litchi orchard where a good number of bee colonies were kept by the bee keepers in order to harvest honey of litchi flowers.
Different type of places was selected in order to count the number of bees on one square metre.
Foraging activities were observed and recorded in four different hours of the day i.e. Morning, noon and afternoon and evening. Every time the foragers are counted numbers of bees in one square metre of Litchi flowers. In order to count the number of foraging visitors the following materials were used-