from Hands-On Nature by J. Lingelbach / Vt. Institute of Natural Science 1986

Surviving the Seasons in Stages

Insects are perhaps the most successful form As it increases in size, the number of cells in the of animal life on this planet. Related to spiders and body does not increase, they merely become larger. lobsters, they are with external Thus the grows, molts several times, and skeletons and jointed legs, but belong to a separate having completed its growth, stops feeding. At this class, Insecta. point it enters a resting state called the . It may There are many reasons why insects have spin a silken covering, such as the cocoon of a , endured and survived through 300 million years of to house itself, or, as in the chrysalis of a climatic and changes. Their small size, the that has shed its outer coat, the pupa may ability of most to , the wide variety of foods they be protected by nothing but a thin membrane. When can eat, and the rapidity with which new this transformation occurs, the larval cells begin to generations are produced all have contributed to die and clusters of adult cells, inactive up to this their continued existence. But there is one especially point, are stimulated by into growth. effective strategy that insects have developed to a During the pupal stage the larval tissues are torn high degree of perfection: metamorphosis. down and slowly rebuilt into organs more suited to Metamorphosis describes the transformation adult life. Essentially the body is reorganized: wings process by which an proceeds from the egg develop, reproductive organs are formed, mouth- stage to that of mature adult. There are two forms of parts change, and most of the muscular system is metamorphosis: incomplete and complete. transformed. The adult then emerges from the pupal Incomplete metamorphosis consists of case ready to reproduce. three stages: egg, , and adult. The newly Metamorphosis greatly contributes to insect hatched insect, or nymph-, usually resembles the survival because it allows flexibility to deal with adult, but it is smaller, and among winged insects, temperature extremes, variable food supplies, the nymphs are wingless. As it grows it molts, droughts, and other harsh conditions. Eggs are often usually several times, shedding the exterior skeleton encased in hard coats that can withstand extreme after having grown a new, larger one underneath it. cold or dryness, and emergence is usually delayed Many nymphs hatch from eggs deposited in the until the proper conditions are available. The larval water and spend their whole nymphal stage feeding stage of any given insect is timed and located to beneath the surface and breathing with . coincide with the appropriate food supply. Colorado and are examples of this. potato larvae hatch out when and where the Nymphs of many aquatic species, when ready to succulent potato leaves are ready to eat, monarch emerge as adults, crawl out of the water, split their emerge a few days after their eggs are skins for the last time, and start breathing in the air laid onto tasty milkweed leaves. For many insects, it as winged adults. Insects having this type of life is in the pupal stage that they are best able to (egg, nymph, adult) include dragonflies, dam– survive extreme conditions, so many insects selflies, bugs, , , and cicadas. over-winter in a pupa or chrysalis. Finally, the adult About 87 percent of all the known insect stage of insects has but one mission, to make sure species go through complete metamorphosis, eggs are laid for the next generation so the species including , , , , , will survive.. Some adults, such as stoneflies and , and . This life cycle consists of four mayflies, live a very short time and do not even have stages: egg, larva, pupa, and adult. The egg hatches eating mouthparts. They mate, lay eggs, and die. into a larva, which does not resemble the adult. It Conversely, in many species of beetles, the adult life often lives in a different habitat from its adult stage is longer than the larval stage, and the adult and usually has chewing mouthparts even though as consumes more food than the larva. an adult it may not. In addition, it lacks its parents' Insect life cycles are adapted to take advan- compound eyes. Larvae have been given several tage of this earth's resources and , while names: fly -maggot; beetle - grub; butterfly and expending a minimum of energy to do so. moth - caterpillar. During this stage the insect feeds. Metamorphosis is one of the reasons why they are It is only during this stage that actual growth occurs. so successful.

METAMORPHOSIS

The Miracle of Metamorphosis

A butterfly has a four-stage life cycle a matter of days. When a proper site composed of egg, larva (caterpillar), is selected, the larva uses to pupa (chrysalis), adult. Each stage has anchor itself to a surface, and then specific requirements. An understanding most species remain motionless for of the life cycles will increase die about 24 hours. Within a period of a pleasure and enjoyment of the butterfly few minutes, the caterpillar skin gardener. A successful butterfly splits and is cast aside and the pupa gardener will use the following emerges. knowledge to his advantage. The pupa hardens into rigid shell Eggs are laid on the leaves of in which larval cells reorganize to specific host plants. A female in search of form the adult butterfly. The pupa is a an egg laying location will taste test non-mobile resting stage. A cocoon is potential sights by tapping them with a silk covering surrounding a pupa her front feet and some–times with her and is produced only by moths. To antennae. If the taste test is satisfactory, protect the pupa from birds and eggs are deposited. If all goes well, the animals, bark and stems should be eggs will hatch in a few days to weeks offered, as many pupa turn brown depending on the species, temperature, and are camouflaged against these and humidity. The larva (caterpillar) has surfaces. Pupation generally lasts a many enemies including bacteria, few weeks if the pupa is formed dur- viruses, spiders, insects, , ing the summer. If pupation takes birds, reptiles, and . Paper place in the fall, the winter is spent as wasps are voracious larval enemies – a pupa. When wing pattern and color- stinging larvae, chewing them into ation shows through, the pupa chunks, and flying the pieces back to die becomes very soft and the adult paper nest to be consumed by the butterfly is soon to emerge. larvae. If one desires to protect butterfly This complete life cycle can be larvae, a woman's stocking or a bag observed in your backyard. Butter. made of fine mesh material can be used flies usually emerge from the pupa in to cover a branch. Don't forget to tic off early morning, mod-is in early even- the end. Larvae can also be raised ing. The adult butterfly generally lives indoors, if the food plants are changed up to two weeks in most species. An frequently. Indoor rearing affords exception is the Monarch which maximum protection. As the caterpillar migrates to Mexico every fall. A few passes through four to five stages of species such as Mourning Cloaks growth the old skin is cast off. These hibernate as adults. stages are called . Specific butterfly species require In many species, the larva changes specific food plants for caterpillars coloration and pattern as it progresses and often a different plant for adult to the pupa stage. When the mature butterfly nectaring. If both needs are larva stops eating, starts wandering and met, butterflies will remain in the fades in color, pupation is usually within area for a longer period of time.