Butterflies emerge from the pupa (chrysalis) with soft wings folded about the body. Over a few hours, the butterfly pumps haemolymph into its wings and they grow to their full length. For many species, males emerge a few days earlier than females and begin to fly. Adult butterflies are constantly looking for food and spend a lot of time looking for a mate to reproduce. They may not have much time. Weather conditions can be poor and many butterflies live for less than a few weeks.
Mating (copula)
Males that find a freshly emerged female will (try to) mate (Fig. 1)
There are different strategies (patrolling and perching) for male butterflies to search for a female, depending of the species.
Pieridae are patrollers, the males fly over areas where the females are feeding or egg-laying. When they find a potential female, they will swoop down to examine the candidate and try to convince the female to mate with them. Males of Pararge aegeria will perch on a plant where females are likely to occur.
The courting ritual can be spectacular and is different from species to species. Some species will fly high in the air (e.g. Colias croceus) but it can also be fighting males. Others will move with the antennae (Leptidea) and Hipparchia are walking around until they face each other. If the female is ready to mate, the male will open his rapidly vibrating wings and after closing the wings again he will trap the females antennae that are rubbed against the androconia of the upperside of the male's upper forewings.
Regularly a copula is harassed (Fig. 2a) by other males. The copula often flies away to escape (Fig. 2b) from the aggressor.
Mating takes time and some species will even overnight as a copula.
Sometimes only one specimen is sitting on a twig and the other butterfly hangs without other support. As well males as females have been seen hanging to their partner.
In Fig. 1a it is a ♀ Aporia crataegi that sits on a twig, in Fig. 3a it is a ♂ Colias caucasica. Sometimes a copula is sitting on warm, well exposed stones (Fig. 4) or walls (Fig. 3b), sometimes the copula is hidden in lush vegetation or shrubs to avoid the heath of the day and aggressors.
Butterflies (Papilionoidea) develop through a process that is called metamorphosis.
Insects have two common types of metamorphosis: an incomplete (the nymph looks like a small wingless adult) or a complete metamorphosis.
Butterflies have a complete metamorphosis in four stages: egg, caterpillar, pupa and adult.
Egg (ovum)
Oviposition starts shortly after mating for short living species that hatch with an abdomen fully loaded with mature eggs.
Species with a longer live may have a more continuous egg production and the egg production per day is low. Many species (e.g. Pieris brassicae) lay a lot of eggs at once, others (e.g. Thecla betulae) lay a few eggs per day over a long period.
Eggs are laid in spring, summer and fall. This depends on the species and the number of generations per year.
This first stage is a small oval or cylindrical egg (Fig. 5; 6a-b; 7a-c; 8a-b; 9), depending on the family and/or species.
Eggs are laid, individually or in clusters, on well selected plants. These different patterns are intended to increase the chances of survival during this vulnerable stage.
The female uses a glue-like substance to stick the egg to the leaf. These plants will become the food for the hatching caterpillar.
Eggs have a small, funnel-shaped opening where the sperm enters the egg and to allow water and air for the developing caterpillar: the micropyle.
An egg contains enough nutrients for the caterpillar to grow inside. The eggs are surrounded by an outer shell, the chorion, to protect the developing caterpillar.
The egg shell has raised ridges or pits that vary greatly in shape.
Eggs typically gestate for one to two weeks. Some species with a single generation (e.g. the Theclinae) overwinter in the egg stage.
Shortly before hatching, it is possible to see the caterpillar inside (Fig. 7b)
When hatching, the caterpillar gnaws open the egg shell with its mandibles (jaws). Caterpillars of many species will eat their egg case as their first meal.
The plant on which the egg is laid is usually the caterpillar's food plant but not always.
♀♀ of Argynnis paphia lay their eggs on the bark of tree trunks but the caterpillars feed on nearby violets.
Caterpillars need to grow quickly so they eat continually. Depending on the species, they consume grasses, leafs or other plant material. The rate of development is highly dependent on the nutritional value of the host plants. Typically, grass eating caterpillars will develop more slowly and produce fewer generations per year.
The exoskeleton is rigid. To expand, the skin will be shed (molt) several times during this growth phase and the appearance of the caterpillar changes significantly (Fig. 10a-c)
The stages between each molt are called instars. The first instar is the caterpillar that hatched from its egg and so on up until pupation.
The food eaten at this stage is necessary for the subsequent transformation of the pupa into an adult stage.
Caterpillars from different families and species can be very different in shape and colours (Fig. 11a-b; 12a-b)
When the caterpillar is full grown it will stop eating and look for a place (branch, in the litter layer, under stones, ...) to pupate, a phase during which the insect will be in a lethargic state for several days (Fig. 13a; Fig. 14a).
The skin of the resting caterpillar tears on the dorsal side (fig. 13b) and immediately after the pupation the butterfly form appears (Fig. 13c)
The shape of the pupae is variable as well as the way they are fixed for stability (Fig. 13c; Fig 14b-c; Fig. 15)
Inside the pupa, the body undergoes a complete cellular transformation. The special cells that were already present in the larval stage, are now growing. They will become the wings, legs, eyes and other parts of the adult butterfly.
Gradually the parts of a butterfly develop and just before hatching the butterfly will be visible inside the almost transparent pupa.
The time spent in the pupal stage varies by species, from a few weeks to months depending on the number of generations of a species and also whether the species hibernates at this stage.
Have you found eggs or a caterpillar? Would like to breed it till the butterfly hatches?
That is an excellent idea and allows you to document really well the life cycle of the species.
There are a number of things you should pay attention to.
1. Foodplant.
Pay attention to the plant where you found the egg or the caterpillar.
It is almost always the host plant. Give these plants as food to the developing caterpillar.
Carefully pick up the egg(s) or the caterpillar(s) on the leaf or twig where they were found.
If the caterpillar was found on the ground, take some plant material (herbs and leaves from trees) from the nearby area.
It often is a caterpillar that is looking for a suitable place to pupate.
2. Tubes for transportation, breeding cages at home.
In the field, the egg(s) and caterpillars can be kept in small tubes (Fig. 16). Add some food and keep the time in the tube as short as possible.
At home you move the eggs and caterpillars to breeding cages (Fig. 17). You can make them yourself and there are also commercial breeding cages available.
Rearing caterpillars is not always easy but it is very satisfying when you finally see the butterfly hatch.
Some species will develop fast, especially from caterpillars found in spring. Others, found in late summer, will overwinter and hatch during the next year.
If you have a lot of space in the garden, it is possible to build a butterfly home cage (Fig. 18) that offers even better possibilities for studying the whole life cycle of the butterflies (Fig. 19-22).
3. Tips and tricks.
Good ventilation is important! Glass jars are less suitable because of condensation, increased mold formation and diseases. Cover the cages with fine gauze.
It is recommended to breed with potted plants. Change the food regularly if you only have leaves, the freshness of the plant is crucial.
Provide upright twigs or other rough surface. Some species will pupate on it, newly hatched butterflies will crawl up to unfold the wings and dry them.
Place a layer of soil in the bottom of the breeding cage and cover it with dry litter (dead leaves, hay, ...). It will absorb excess humidity and droppings from the caterpillars.
Remove caterpillar droppings regularly, otherwise mold formatioin and diseases may develop.
Keep the cages well closed. Caterpillars are masters in escaping. The cover with fine gauze will also prevent parasitic wasps from entering.
Place the breeding cage in an unheated and quite dry space. Do not breed in a heated room that leads to an unnaturally early hatching of the butterfly.
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