A Students Guide to
Butterflies
Module 5: Relationship to Plants
Having mated, the female butterflies lay their eggs on the leaves and stems of particular plants. The females use the sensory capabilities in their antennae to detect their correct host plant. Upon emerging from the ova (egg) the larvae (caterpillars) will proceed to eat the leaves of the plants they were laid on. These plants are called host plants.
The relationship between any given butterfly species and it's host plant(s) is very specific, and specific for very good reasons. Many butterlies will lay their eggs on a single species of plants, whereas most will prefer groups of very closely related plants. From the host plants is where the larvae obtain all the necessary nutrients and chemicals they need to produce their colors and other characteristics as adults. For example, the butterflies which are toxic in their adult stages (see Defense Mechanisms) depend upon their specific host plants for ingesting and accumulating these toxins. In the example of the Monarch which feeds on milkweed (Asclepias), the larva will slowly accumulate toxins from the leaves in amounts which it can handle. Then, as the larva becomes an adult, it carries these toxins with it and is poisoness to any predators that would feed on it. In this manner, many butterflies are dependent upon toxic plants in order to be toxic to predators.
Some of the butterfly - host plant
relationships for some common Costa Rican species are as
follows.
| Butterfly genus | Host plant |
|---|---|
| Parides sp. | Aristolochia |
| Battus polydamus | |
| Anteos chlorinde | Cassia |
| Phoebis sp. | |
| Hamadryas sp. | Dalechampia |
| Adelpha fessonia | Randia |
| Papilio thoas | Piperaceae |
| Papilio cresphontes | Citrus |
| Dione juno | Passiflora |
| Agraulis vanillae | |
| Dryas iulia | |
| Heliconius sp. | |
| Caligo sp. | Musa, Heliconia |
| Danaus plexippus (Monarch) | Asclepias (Milkweed) |
Butterflies, their Habitats, and Conservation
People from all parts of the world often wonder, What happened to the butterflies that we saw when we were children? The sad but true answer to this question is that they are gone. As mankind cultivates the land, builds roads, houses, shopping centers and butterfly exhibits, he is fundamentally changing the landscape. Forested and other natural habitats are destroyed, and so too are butterfly host-plants which are generally taken for useless weeds. So as we progress, butterfly populations and wildlife in general regress.
In order to protect the butterflies and other wildlife of the world, we as humans need to take a step back and look at the footprint we are leaving on our surroundings. In the example of butterflies, the logical first step in protecting them is to not collect and kill them, or to limit the amount of insecticides we use on our crops. While these are both valid steps toward protecting butterflies, we must focus more of our attention on their habitat. Without sufficient areas of natural habitats that contain the host plants to sustain the larvae, their will be no butterflies. As humans we need to recognize this dilemma as we decide how we are using our land and natural resources.
A very common question in the guided tour here at The Butterfly Farm in Costa Rica is: Why aren't you breeding rare or endangered species and releasing them into the wild?. The answer to this question involves this same concept of habitat destuction described above. Even if we were to breed hundreds upon hundreds of endangered species here at the farm for releasing in the wild, the effect on the number of individuals in the wild would be very insignificant. The number of butterflies of a certain species in the wild is reflective of the size of its habitat. Therefore, to increase populations of endangered species in the wild, we need to increase the habitat of that butterfly first.
Migratory Butterflies
Lets start with a very brief description of non migratory butterflies. A female hatches out of the pupa and her program says to mate and begin laying eggs right away in the immediate location. Every female of this species has this program. They will quickly seek a male, mate, and lay their eggs on the host-plant.
A migratory butterfly however, has a different program. The big question is where does this program come from? Also, what triggers the running of the program which, in turn, makes the butterflies leave their present location and head for another. It could be climate conditions , or temperature, or an internal clock that sends them on their way.
For most of the rainy season, the butterflies of the Pacific coast in Costa Rica have a program that says lay your eggs in the same area where you hatched. So, the butterflies live their lives in the same place. At the end of the rains, the females that come out have a different program that says seek out the rains and lay your eggs there. Off they go to the Atlantic slope and there they will stay until the rains return the following year. Essentially, they are searching for the ideal climate to reproduce themselves.
Now for the Monarchs. The monarch feeds on milkweed. The milkweed needs warmth and moisture to grow. At the end of the summer in southern Canada and the northern United States, Monarchs come out of the cocoon and their program says winter is coming here soon, you must seek warmth and lay your eggs next spring. They seek warmth by flying down to Mexico. They arrive in November. There are literally millions of them. They will sit on these trees until springtime when the first milkweed of the new year is coming out along the Gulf of Mexico. When that happens, they will fly there, lay their eggs, and die. Realize that butterfly just lived 9 months and flew nearly 5,000 kilometers. If that's what it takes for the species to exist, that's what it will do.
These eggs on the Gulf of Mexico will mature and fly to the central (north-south) of the United States. Because their journey is not as long, they don't live as long. They will fly for a couple of weeks, lay their eggs at their destination and die.
The next generation will do the same. Notice that they are moving up the states at the same pace as spring and summer. They are following a constant climate. This generation comes out at the end of the summer and they have the same program as their great grandparents did. They fly all the way back to Mexico where they will wait out the next spring.
The Monarchs of Costa Rica are non-migratory because their need for a warm climate is always satisfied. They live three weeks and lay their eggs in the local area.
This information is provided by Evan Fitzgerald, who was an intern at The Butterfly Farm in 1999. Evan graduated from the University of New Hampshire with a Bachelor's Degree in Environmental Science in May 1998. Evan can be reached at: evan@butterflyfarm.co.cr.
