12. How do Monarch butterflies breathe?
When we breathe, oxygen goes into our lungs and is picked up by blood which carries it to cells throughout our body. Because we are relatively large, we need this complicated system. But insects are so small that tiny air tubes (called tracheae) carry air from the outside directly to body tissues. Air enters and leaves these tubes through small holes (called spiracles) on the outside of the thorax and abdomen. Spiracles are easily seen on larvae and pupae but are difficult to see on adults because they are obscured by scales. [Back to FAQs]

13. Why do Monarch butterflies all have the same design on their wings?
The design or pattern on the monarch's wings is genetically programed. This means that the pattern is determined by genetic rather than environmental factors. The color of our eyes and hair is genetically determined but our height and weight are partly determined by environmental factors such as the amount and quality of food we eat. The pattern on the wings of Monarchs is not influenced by the temperatures during larval and pupal development, nor the food plants upon which the larvae feed, however, the size of the adult butterflies is related to the quantity and quality of the leaves the larvae have fed on. [Back to FAQs]

14. Why do Monarchs have this particular design on their wings?
Colors and patterns of insects are thought to be the result of interactions of each species with their environment. Charles Darwin noted that "evolution is written on the wings of butterflies". By this statement he suggests that the colors and patterns on butterfly wings are the result of long term evolution. Is this true? Well, we don't have a complete understanding of how evolution works in these cases but there are numerous studies of butterflies which demonstrate many functions for color and pattern. For example, in some species color and pattern are used by individuals to recognize members of the same species for mating. Bright and/or contrasting colors, such as the black and orange of the Monarchs wings, warn predators that the insects are distasteful (Monarchs are distasteful to many predators due to the chemicals, cardenolides, they acquire from feeding on milkweeds) and, in some cases, dangerous (certain caterpillars with urticating hairs). These contrasting or warning colors are also the basis for mimicry in butterflies and other insects. Butterflies which are distasteful to predators usually have warning colors and patterns on the wings and these species serve as models for mimicry by other insects which are not distasteful to predators. Mimicry seems to work because the predators learn to avoid the color/pattern of the models and this avoidance gives protection to the mimics. In addition to communication within and between species, colors and black (melanic) pigment can also serve to maximize and minimize heat gain due to adsorption of infrared energy from sunlight. Insects tend to be more melanic and "hairier" in mountainous areas and far northern latitudes, where temperatures are low. Black pigments, particularly at the base of the wings, have been shown to enhance convective heat gain from the sun. Tropical species which frequent open, sunny habitats tend to be light in color while those which reside within the forest are usually darker. Within forests, darker colors can help conceal the insects from predators but some species also appear to use these colors to adsorb heat since they are often seen to "sun" themselves in patches of sunlight when temperatures are low. [Back to FAQs]

15. If caterpillars can chew leaves why can't adult Monarchs do this?
In the pupal or chrysalis stage, the Monarch goes through many transformations. One of the most interesting changes is the alteration of the mouthparts. In the larva, the mouthparts are designed to taste, cut, chew and ingest the leaves they feed on. During development in the pupal stage these mouthparts are modified to form a long tubular proboscis which the adults use to obtain nectar and water. These changes from chewing to sucking mouthparts during metamorphosis are unique to the Lepidoptera and Siphonaptera (fleas). Curiously, one small group of primitive moths (Micropterygidae) retains chewing mouthparts in the adults and in several other groups the mouthparts are reduced and non-functional. Why and how these changes from leaf feeding to sucking mouthparts evolved is not clear but an obvious advantage is that the adults are able to use other resources and are not dependent on their larval hostplants. Adult butterflies obtain carbohydrates and small quantities of amino acids and minerals from nectar; a sparse diet compared to the protein, lipid, carbohydrate and vitamin rich leaf materials consumed by larvae. This shift in diet from leaf to nectar feeding allows butterflies to range over broad areas. [Back to FAQs]

16. How do Monarchs get those little scales on their wings and body?
The scales form during the pupal stage of all Lepidoptera. This group of insects is named after the presence of scales; lepid-optera means scaly wings. Among the insects, only Lepidoptera have so many scales - their nearest relatives, caddisflies (Trichoptera), have relatively few scales. Scales are thought to be modified hairs but what would be the advantages of such modifications? It's hard to know how selection worked to make the conversions from hairs to scales but scales seem to have many advantages over hairs. In flight, scales probably lessen wind drag and may even contribute to lift. They also protect the butterflies by reducing water and heat loss and, depending on their color, they can aid in maximizing or minimizing heat gain. Scales may also reduce the amount of injury to the wing membrane. Scales usually contain pigments and the deposition of various pigments among scales in different regions of the wings give rise to the colors and patterns used for concealment, warning coloration, species recognition and thermoregulation. In some species, including Monarchs and their relatives, scales have been modified to disseminate pheromones (odors used for communication within species). [Back to FAQs]

17. Do caterpillars and butterflies have bones?
No. All insects have an exoskeleton, a hard covering or special skin (cuticle), which provides support and protects them from water loss. Because of their high surface to volume ratio, insects have the potential to loose water rapidly. The hard cuticle is coated with waxes (long chain hydrocarbons similar to those found in beeswax) which minimizes water loss. [Back to FAQs]

18. Why do butterflies have to be in a chrysalis before they are born?
Butterflies and moths have complete metamorphosis, which means they have four separate life stages: egg, larva (or caterpillar), pupa (or chrysalis in butterflies), and adult. The pupa is a special stage during which the tissues of the larva become reorganized and transformed into those of the adult butterfly. The changes from larva to adult are so extensive that they appear to require this intermediate or resting stage. [Back to FAQs]

19. Why do Monarch butterflies rest in groups on branches during the migration and while they are at the roost sites in Mexico?
The advantages of clustering behavior by migrating and overwintering Monarchs are not well understood. There are several possible explanations. Clustering could simply be an artifact of too many butterflies having a preference for the same type of resting spot. Or, perhaps, it's a follow-the-leader type of behavior in which some butterflies find a good spot and others join them. Temperature and predation may also influence clustering. This past fall ('95) we observed that clusters which formed late in the day appeared to be tighter on evenings with cooler temperatures. Why? Once Monarchs are on the roosts, and have cooled to ambient temperature, no heat is generated by the cluster. So, what are the advantages of such tight clusters? Is heat gain from the sun or from "shivering" the next morning greater in clusters? And, are tightly clustered Monarchs therefore able to become active earlier in the day than those Monarchs which are isolated? What about predation? Is there a "startle effect" and an improved chance of escape if predators attack a large cluster rather than a small one? Clustering could have several advantages but so far there are no studies of this behavior. This is an example of the many unanswered questions we have about insect behavior. [Back to FAQs]

20. How high can a Monarch fly?
Monarchs have been reported by glider pilots at 1250 meters (4062 feet - that's about 3/4 of a mile above the earth's surface!). And, commercial and military pilots have seen Monarchs at 3000-4000 meters over midwestern states in September. How do they get this high? They probably take advantage of bubbles (or columns) of warm air (thermals) just as birds do (e.g. hawks, eagles, vultures). If you watch migrating Monarchs in the fall, you can often see them shift from directional flight to one in which they circle, usually with the wings set in a fixed position. With each circle they rise and soar in a pattern which we usually associate with hawks.. At the top of the bubble or thermal they resume their directional flight. This behavior is most easily observed in the morning when wind speeds are low. Winds tend to break up the weaker thermals and displace the butterflies so the Monarchs probably only reach high altitudes under very special conditions. [Back to FAQs]