The Karner blue has a different diet during its larvae stage in comparison to its adult stage. The larva only eats wild lupine (Lupinus perennis) whereas the adult Karner blues mainly feed on the nectar of a variety of different flowering plants. Some adults have also been observed obtaining salts and minerals by sipping on the water of moist ground, on human perspiration, as well as some males feeding on animal droppings (Animal Diversity Web 2013).


     Not only is the wild lupine important in the nutrition and diet of the Karner blue larvae, but it is the one plant that the Karner blue structures its whole life cycle around. After the caterpillar hatches it will feed excessively on the wild lupine for approximately three weeks. After three weeks the caterpillar will pupate and later emerge as an adult butterfly. During the Karner blue’s short lifespan as an adult it will mate as well as hatch eggs near the wild lupines so that the hatching larva will be able to eat and survive (ehow 2013).


     The abundance of wild lupine has been greatly decreasing over the past years. Wild lupines depend on Pine Barrens to grow. Years ago there was no shortage of Pine Barrens for the wild lupines to habitate, but with the increase of deforestation there is a lack of regions for the wild lupines to grow. This decrease in wild lupines then causes a decrease in Karner blue populations because there is not enough food to feed the larvae. The limited food choice of the Karner blue larvae is one of the main reasons that the species is currently nearing extinction at a rapid rate (U.S. Fish and Wildlife Services 2012). The Karner blue’s diet is crucial to its survival as a species and it is crucial that something is done to help decrease the rate of pine barren loss and in turn increase the production of wild lupines.


     Observational studies have been conducted in order to evaluate the types of wild lupines and nectars that are preferred by the Karner blue. It was noticed that larvae prefer to eat wild lupines which have longer, thicker stems as well as larger leaves (Animal Diversity Web 2013).  Not only was a preference of vegetation noticed in the larvae but the adult Karner blue have also shown patterns in their selection of  nectar plant species. An observational study conducted in Wisconsin found that the Karner blues feed on as many as 36 different nectar producing plants. The researchers of this study found that the adult butterfly of the Karner blue chooses its plants based on abundance of flowers, location of the plant in shade or sunshine, as well as color of the flowering plant. It was found that plant species with the most flowers were selected 60% of the time and that the butterflies were more likely to choose species that had yellow or white petal coloring. It was also shown that male Karner blues prefer plants that are in the open whereas adult females prefer  plant species that are nearer to shade. They also found that the abundance or accessibility of a species of plant had no effect on the amount of times it was selected by the adult butterflies. These studies not only showed tendencies when it comes to plant type but it was also notices that different broods (meaning the different times of the year that the butterfly hatched) as well as the sex of the butterfly made a difference of the likelihood of certain nectar producing plant species to be chosen (Grundel, R., Pavlovic, N.B., and Sulzman, C.L. 2000).


     These types of observational studies are very useful because the information obtained can help plan more productive and effective conservation management programs. With the information of which nectar producing plant species an adult Karner blue is likely to choose, those types of plant species can be strategically grown in order to create an optimal feeding habitat for conservation of the Karner blue species.


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