The Effect the Type of Food has on the Pupation Period of Painted Lady Butterflies August 1, 2000 Group 2 The Millennium Exotics Jena Greenman Zakiya Grubbs Grace Kaissal Dorothy Legros Bobbie McGruder Haris Sayeed
Introduction The type of food eaten by a butterfly can have serious effects on its life. This is because not all larvae can live on the same type of food. The painted lady butterflies feed on the host plants Malva. Young larvae like to eat radish leaf, hollyhock, and Malva. This is in addition to the commercial food with which they come packaged. For our project we decided to test the effect hibiscus leaves would have on the young larvae as opposed to the commercial food. The species we are studying is Vanessa cardui, commonly known as the Painted Lady Butterfly. The Painted Lady is the most common butterfly in the world. Its life cycle takes approximately 3 weeks. This is about 7-10 days in the larval stage and 7-10 days in the pupa stage, which we are measuring. The female butterfly can lay up to 500 eggs in adulthood. Her normal life span is from about 2 to 4 weeks. (Insect Lore) Our independent variable, the type of food eaten, can have a great impact on the growth of the butterflies. We are testing the hibiscus leaves vs. the commercial food. Organisms use food for energy. If the food is appropriate our Painted Lady Butterflies can use it as energy for growth. (Lugo, pers. comm.) We predict that the larvae fed with commercial food will pupate and hatch faster than those fed with the hibiscus leaves. A null hypothesis would be that there would be no difference between the growth of the larvae fed hibiscus leaves as opposed to the ones fed the commercial food. The alternate hypothesis is that there will be a significant difference between the two groups.
Methods Our experiment consisted of 30 organisms, 15 in the treatment group and 15 in the control group. The larvae in the treatment group were fed hibiscus leaves and the ones in the control group were given commercial food. The hibiscus leaves used were taken from the side of the Cox Science Center building. We took 12 leaves and washed them with soap and water. Lastly we dried them, cut them into small pieces, and placed them into the cups that came with the kit. The commercial food was also evenly placed in the remaining 15 cups. The rest of the conditions in our experiment were kept constant for both groups. There was a 12 hour light period for both groups, 7am to 7pm. The temperature was the same for both groups, normal room temperature (24 degrees Celsius). There were equal weights of food given to all of the larvae, 2.5 grams of either hibiscus leaves or commercial food. The food was placed in each of the small containers, which were the same for all the organisms. The only difference between the treatment group and the control group is the type of food. To test the effect of it we will measure the amount of days our butterfly will spend in the pupa stage. To analyze our data we will get the average number of days for each group and the variance. We cannot perform any statistical test because we don t have two sets of data to compare. Results For our treatment group, we were not able to collect the desired data. The average number of days spent in the pupa stage was 0 for the treatment group, and 8.5 for the control group. (Fig. 1.1). All the larvae in our treatment group died before reaching the pupa stage. (Fig. 1.2). For our control group, the butterflies spent an average of 8.5 days in the pupa stage with a
variance of 0.2778. (Fig. 1.2). It was impossible for us to perform any statistical test because there is only one set of data; there is nothing to which we can compare this data We can still accept our alternate hypothesis that the type of food was significant in the growth of the caterpillars. According to these results it is evident that the butterflies grow better while eating commercial food as opposed to hibiscus leaves. We accept our alternate hypothesis. The type of food did have a substantial effect survival of the larvae. Discussion We reject our null hypothesis and accept our hypothesis that the food would have an effect on the growth of our larvae. The results followed our predictions to a certain extent. We predicted that the butterflies in our control group would pupate faster, but we didn t imagine that the butterflies in our treatment group would die within two days. Obviously, the caterpillars eating the commercial food survived and grew as expected. Those that ate the hibiscus leaves died. We can attribute this to many possible factors. We suspect the main problem was that the leaves had some lethal contaminant. Possibly, we didn t wash them well enough and they had remains of any insecticide or pesticide when fed to the larvae. Or, another possibility is that we didn t rinse it off properly leaving soap residues. Another alternative, although less likely, is that they died of starvation. Maybe the hibiscus leaves weren t tasty to them. They were better adapted to the commercial food. If we were to design a similar experiment again we would select a different type of plant leaf. Also, we would make sure that the leaves were properly washed. A good alternative would be to do an experiment where we use radish leaves vs. commercial food. It is known that V. cardui larvae like radish leaves. We can purchase them from a food store where we will know that they will have no remains of pesticides or anything similar. Measuring the length of the
pupa stage is still a good measure of growth. The larvae eat the food and all the energy that they gain from it they use it to pupate. The better the food is to them, the faster they ll pupate. In conclusion, the butterflies that are fed commercial food grow faster and survive. But the ones fed hibiscus leaves didn t. This last group died before developing.