Question

Bean beetles (Callosobruchus maculatus) are agricultural pest insects of Africa and Asia. Females lay their eggs on the surface of beans (Family Fabaceae). Eggs are deposited singly and several days after deposition, a beetle larva (maggot) burrows into the bean. At 30°C, pupation and emergence of an adult beetle occurs 21–30 days after an egg was deposited. Adults are mature 24–36 hours after emergence and they do not need to feed. Adults may live for 1–2 weeks, during which time mating and oviposition (laying of eggs) occurs. Since larvae cannot move from the bean on which an egg was deposited, the oviposition choice of a female determines the future food resources available to their offspring. As a result, it is the most critical choice a female makes for her offspring, because it will influence their growth, survival, and future reproduction. Although females can be induced to lay eggs on a wide range of bean species, very few bean species result in normal development and the successful emergence of adults.

1. What is the test organism/experimental unit/subject in this experiment?

2. What is/are the dependant variable(s) in this experiment?

3. For a chi-square analysis how many degrees of freedom are present in this study?

Answer 1

1.Bean beetles from genus Callosobruchus are pests that can survive without food or water mostly found in Asia and Africa. The females of these insects lay eggs on beans and the larvae feeds on the bean embryo. Here the test organism is female bean beetles and the subject to test can be the preference of beans for female bean beetles for the survival and reproductive success of the larvae. For an experiment different types of beans can be selected to find the preference of bean by this type of insects. Female bean beetles might be sensitive to the type, species and condition of beans on which they lay eggs.

2.The dependent variable here is the life span of the offspring of the beetles. The independent variable is the types of bean species.

3.To perform Chi2 analysis, determine the calculated value of the experiment and the critical value. As no experiment is specified here the number of bean species or independent variables for the experiment is used to calculate the degree of freedom. For example if the bean sample were 'n' on a chi-square test, then the degrees of freedom to be used in calculations would be n - 1.