The Apterygote (wingless) insects
These are the Diplura (bristletails), Collembola (springtails), Protura and Thysanura (silverfish).
The bristletails and silverfish both have two long cerci, and
between this a caudal appendage. There are just under 10 000 described species
Class Pterygota (winged) insects
These insects have two pairs of wings; one pair on
the mesothorax and another on the metathorax. Pterygotes have muscles which
allow them to close their spiracles so greatly reducing water loss and enabling
them to colonize drier habitats.
The Pterygotes can be
further divided into two groups; those that undergo complete metamorphosis
(holometabolous). A typical holometabolous insect the brown house moth, Hofmannophila pseudospretella shown on the right in the various stages of its life. And those that undergo a gradual metamorphosis (hemimetabolous).
Hemimetabolous insects have young that resemble the adults,
and the gradual development of wings is external . Such insects include, Cimex lectularius (the bed bug) above, which shows the gradual change to the adult form, also Odonata (dragonflies), Orthoptera (grasshoppers), Dermaptera (earwigs) and Hemiptera (aphids, cicadas.
Holometabolous insects have
young (larva) that usually do not resemble the adult (see above), and often
occupy a different niche. These insects form a pupa (see above) before emerging
as the adult form.
About 88% of the described insects are holometabolous and
include the four largest Orders that have diversified along with the
diversification and radiation of the Angiosperms; they are the Diptera (flies), Coleoptera (beetles), Hymenoptera (wasps, ants, bees), and Lepidoptera (butterflies and moths).
Insects as pollinators.
Importance of insects
Nutrient recycling. In leaf litter (Coleoptera
, etc.), dead and live wood (Coleoptera
, etc.), carrion (Coleoptera
), dung (Coleoptera
), soil (Collembolla
Maintaining the balance in plant communities by phytophagy.
As food for insectivores, e. g. mammals, fish, birds etc.
Insect behaviour patterns.
Courtship. This usually involves males trying to attract females. The female behaviour is simply to accept or reject, e.g. during courtship the male scorpion fly presents the female with a dead insect which she eats during copulation.
Copulation. Copulation is the physical joining of the male and female culminating in the passing of sperm from the male to the female, e.g. bumblebees.
Egg-laying. Most species have very specific site requirements for egg-laying, so that the eggs are laid on, in or near the source of food for the larva or nymph, e.g. dung beetles.
Defence. Defence can be active, e.g. sting (bees, wasps, etc.), bite (beetles, etc.), chemicals (bombardier beetle); or passive e.g. hiding (cockroach), camouflage (stick insect).
Communication. Communication is the transfer of information between individuals - usually of the same species, e.g. honeybees communicating the location of a good food source.
Grooming. This is especially important in hairy insects, e.g. bumblebees. These and all others need to keep their antennae, eyes, wings, legs and mouthparts clean. Most have a brush or comb on their forelegs, e.g. bumblebees, that can be used to cleans antennae and legs.
(Odonata: Aeshnidae), a dragonfly at 98 km/h
Hybomitra hinei wrighti
(Diptera: Tabanidae), a fly at 145 km/h
|Fastest wing beat
|| Forcipomyia sp.
(Diptera:Ceratopogonidae), a midge, species not known can beat its wings 1046
times per second.
||Cicindela hudsoni, an
Australian tiger beetle can run at 2.5 metres per second.
|Least specific vertebrate
(Diptera: Glossinidae), tsetse fly. It can feed on any vertebrate.
||Pharnacia serratipes, a
stick insect, at 55.5 cm (22 in).
echmepterygis (Hymenoptera: Mymaridae), a parasitic wasp. The length of the
male is 139 µm.
the desert locust. In 1954 a swarm covering 200 km sq invaded Kenya. The swarm
was estimated to contain 10 billion individuals.
|| Xylocopa auripennis, a
lays eggs 16.5 mm long and 3.0 mm in diameter.
(Hymenoptera: Formicidae), a Saharan ant which can forage at body temperature
above 50oC and surface temperature of up to
vanderplanki (Diptera), an African chironomid (midge) can survive submersion
in liquid helium at -270oC.
(Hymenoptera), the honey bee. The drone (male) dies after mating once. The
queen bee files off with his phallus still in her vagina. The phallus having
broken off after sperm exits explosively. The queen eventually ejects the
phallus and goes on to mate again.
(Lepidoptera: Danaidae), the monarch butterfly. Some migrate more than 4000 km
from Southern Canada to Central Mexico. It now looks likely that the longest migration is by dragonflies who make a 14 000 - 18 000 km round trip from India to southern Africa stopping off at the Maldives and the Seychelles.
|Longest adult life
||Lasius niger, ant queen
survived 28.75 years in captivity.
Pogonomyrmex owyheei, ant queen,
30 estimated in the wild.
|Longest life cycle
larva, a wood boring beetle, emerged after 51 years
(Ephemeroptera), a mayfly, lives for less than five minutes after her final
molt. During the five minutes she chooses a mate, mates, and lays her eggs.
prunifolia, an aphid, has the shortest generation time of 4.7 days at
|Most polyandrous (female with
highest number of mates)
(Hymenoptera:Apidae) a queen bee mated 53 times, each with a different male.
Chrysochus cobaltinus (Coleoptera: Chrysomelidae), a blue milkweed
butterfly female, had up to 60 matings, though some of these were multiple
matings with the same male.
(Homoptera: Cicadidae), a cicada, produces a calling song with a mean sound
pressure level of 106.7 decibels at a distance of 50 cm.
|Best "new" man
orbicollis, a burying beetle, participate in all activities, remain with
the brood throughout development, and can take over all parenting
responsibilities if the female disappears.
|The above insect records,
taken from Walker,
T.J., ed. 2001. University of Florida Book of Insect Records,
||Termes panamensis, (a termite) has the fastest muscles in the world. It needed film shot at 40 000 frames per second to calculate the speed at which T. panamensis snaps its jaws shut, and the result is 70.4 m s-1. Its jaw muscles are so big that they fill half the space inside its head, and they are triggered by seeing an intruder's face inside the nest.
|Longest sexual intercourse
||In many stick insect species males are never or hardly ever seen, however in other species the males can maintain intercourse for months at a time.
4 main functions of a sense of smell in insects, plus examples
||Gathering of male moths to a female releasing a pheromone
|Recognition of nest mates
||Ants, bees and wasps recognise nest mates and intruders. Ants lay down trails between nest and food source.
|Egg laying attractants
||Blowflies and carrion beetles are attracted to rotting meat as this provides a food source and habitat for larvae.
||Dung beetles attracted to the smell of dung as a food source and also as an egg laying site.