The dictionary says that
the plural for "pupa" is either "pupae" or "pupas." When I
was a kid we were obliged to call them pupae but nowadays I think most people call them
pupas. Anyway, here we are speaking of the resting stage
between the larva and adult stages of insect species undergoing complete metamorphosis.Pupal stages vary dramatically in appearance from insect group to insect
group. For example, the pupae of many butterflies develop into beautiful chrysalises
(singular chrysalis),The picture at the right shows one of the most famous chrysalises,
that of the Monarch Butterfly. This picture is especially nice because
you can see the Monarch's orange and black wings inside the pupa's shell.

The above, of a Black Swallowtail chrysalis
also is nice for the same reason. Note the future adult's segmented abdomen and, at the
lower left, the enlarging wings. You can even see veins in the future wings. This
chrysalis was found stuck by the silk at the picture's lower left onto a piece of plywood
leaning up against a house! If you should find such a thing, the best would be to let it
stay, and watch it develop each day. You can also put a pin through the silk -- but not
through the chrysalis itself -- and hang it where you can watch it more closely. At the
right is the abandoned, split-open "skin" of the same chrysalis shown above,
after the adult Black Swallowtail butterfly emerged a week later.
At the left is the chrysalis of the Gulf
Fritillary butterfly. Gulf Fritillary larvae feed on Passionflower vines. The
species ranges all the way from Argentina to New Jersey and Iowa in the US.
Some
chrysalises are beautifully camouflaged, such as the one at the right. That's the Polydamas
Swallowtail, the larvae of which eat Aristolochia vines. This species
occurs in the US Gulf States, into Mexico. Polydamas larvae are mostly black, so you
can see that you can't depend on the appearance of a larvae cueing you as to how the pupa
may look. Notice how this chrysalis attaches itself to the plant stem. In the top,right
corner of the picture you can barely see two thin silk strands connecting the chrysalis
with the stem.
Some
pupae develop inside cocoons, such as the one at the left, which was
constructed by one of the large, showy Giant Silkworm Moths. The cocoon
is held together by silk spun by the caterpillar before entering its resting pupal stage.
This cocoon is suspended at the tip of a slender tree branch. The cocoon is empty, with a
hole at the top, where the adult moth emerged. Notice the neat way that a leaf has been
incorporated into the cocoon, the leaf's midrib clearly visible bending around the
cocoon's bottom.
A bagworm cocoon
is shown at the right. Sometimes you can spot a bag slowly creeping along a
stem. The larva is mostly hidden inside the bag, where its soft body is protected from
birds who might want to eat it. Just enough of the larva's body sticks through a hole in
the top of the bag to enable the larva to move the whole bag along a stem to a new
location where there's plenty of greenery to eat! Once the larva eats and matures enough, then
it turns into a pupa, and while it's in the pupa stage the bag stays in one place and
protects it. Then one day the bag splits and out comes the adult moth.
By the way, the bagworm cocoon in the picture was found on a twig of
Loblolly Pine and if you look closely you can see that some pieces pine needles have been
incorporated into the bag. If the bag had been on a Redcedar, then Redcedar scales would
adorn the bag. The whitish splotches are lichens that have established themselves on the
bag, and this shows that this particular bag has been in service for several months! This
bag is about two inches (five cm) long.
At the left you see the nests of a Mud-dauber Wasp
(family Sphecidae, subfamily Trypoxyloninae). Mud daubers
construct such nests from mud. The nests are partitioned off with mud and each cell is
provisioned with several paralyzed spiders and implanted with an egg. After the eggs hatch the larvae feed on the
spiders, and mature in about three weeks. Then the larvae spin a cocoon inside the
dried-mud nest and overwinter. Pupation occurs within the cocoon while it's still
inside the cell. Sometimes overwintering mud dauber nests fall off, as the one shown at
the right did, and you can see into the nest's cells. Can you see the smooth, dark-gray
cocoons inside the cells? The cells at the bottom, right and top, middle, are
empty, for comparison.
By the way, mud daubers are very different from social wasps
(hornets, yellowjackets and paper wasps) in that there is no worker caste and the queens
must care for their own young. You don't need to worry much about being stung by mud
daubers because the wasp queens use their sting to paralyze their prey (spiders) rather
than to defend their nests. Also, the wasps in general are not aggressive and they rarely
sting unless touched or caught in clothing. |