Ch 28-4 – Insects and Their Relatives

Uniramians – Centipedes, millipedes and insects

Characterized by one pair of antennae and appendages that don’t branch

Centipede and Millipede

• Wormlike body• Many leg-bearing

segments

centipede millipede

Centipedes• Carnivores• Poison claws in

head• Eat arthropods,

earthworms, snakes, mice

• Have ONE pair of legs per segment (not necessarily 100 legs!)

• Have venomous bites against predators

Cenitpede eating tarantula

Centipede poison claw

Centiped protecting hatchling

Millipede• Two pair of legs

per segment• Herbivores• Feed on dead and

dying plant material

• Protect themselves by rolling into a ball or use “nasty chemicals” to dissuade their predators

Millipedes

MillipedeMillipede

Many legs!!

MillipedeMillipede

Millipede eating

Protection

Insects

• Have 3-part body• 3 pairs of legs

attached to thorax

Feeding

• 3 pairs of appendages used as mouthparts

• One is the mandible

• Amazing modifications of the mouthparts

mouthparts

• Other modifications for feeding – mosquitos saliva – anticoagulant

• Bees legs and bodies are covered in hair for collecting pollen

• Bees have glands in abdomen that secrete wax to build bee hives for food storage and larvae nurseries

• Bee saliva changes nectar into honey

movement• Three pairs of

walking legs are greatly varied

• Many insects have highly specialized legs for jumping and capturing prey

flight

• Flying ability varies greatly

• Butterflies have limited manoeuvrability

• Certain flies, bees and moths can fly extremely well

• Thorax is filled with large muscles for wings

Adaptations for flight

• Enlarged thorax for muscles

• Oversized mitochondria supply muscle cells with energy

• Special blood supply to wing muscles keep muscles warm (sometimes warmer than outside) for optimal efficiency

Clear wing Clear wing butterflybutterfly

Insect colonies• Collections of

individuals of the same species that live together

• SOCIETIES are colonies where individuals are DEPENDENT on the others for survival

ANTS!

Ant ColonyAnt Colony

• Termites, wasps, bees and ants form societies

• Have division of labour

• Different individuals (called castes) will have specialized bodies to perform their task in the society

• Examples of castes:

• reproductive females (queens)

• reproductive males

• Workers• warriors

TermiteQueen

workers

Termite soldier

Worker

QUEEN

• Reproductive males ONLY fertilize the eggs

• In BEE SOCIETIES, the queen mates with one or more males only ONCE.

• She receives all the sperm she needs in that mating

• The successful reproductive male then dies

• All unsuccessful reproductive males are turned out of the hive, and soon die

• Workers do all the work for the hive

• Bee workers are all female and are able to do all jobs (except reproduce)

• Ant and termite workers are specialized for specific jobs

Insect Communication• Non-social insects

communicate mainly to find mate only

• Cricket males rub their forelegs together

• Male cicadas buzz by vibrating a membrane on their abdomen

• Male fireflies produce a series of light flashes

• The wingless females (glow worms) flash back their reply, and the males will find them

• (sometimes another genus will mimic this signal and prey on the expectant male)

• Many female moths produce pheromones to attract their male

• Social insects have more complicated communication systems

• Pheromones are often used

• Ex. Ants drag their abdomen all the way home from a food source to leave a trail for other ants to find the food

• The Queen Bee produces “queen substance” that prevents other females being able to lay eggs

• When queen substance is low in the hive, the worker bees will feed a few female larvae a special diet which causes these larvae to develop into queens

• Worker bees “dance” to tell other workers where they found food

• Two basic dances: the round dance and the waggle dance

The Round Dance• The bee walks in a circle, then retraces that circle in the opposite direction

• Means that food is within 50 meters of the hive

• Good quality food will be indicated by more frequent changes of direction

• The kind of flower found is determined by smelling the messenger

The Waggle Dance• The bee wiggles her abdomen while walking in a straight line

• She circles around and wiggles back up the same line

• She will then circle around on the other side of the line, and repeats

• The waggle dance means that the food source found is more than 50 meters away from the hive

• The direction of the straight line is the direction the other bees must travel away from the hive to find the food

1 million species of insects have been identified so far, which is about ½ of all animals known to science

Sizes could vary from .25mm to 50 cm

Many male insects have appendages called claspers, which help them stay in position during mating.

Centipedes