PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
REPRODUCTION
MALES AND
FEMALES
HOW DO EGGS
HATCH?
MOST INSECTS HAVE MALES AND FEMALES
Male insects produce sperm and females produce eggs.
Most insects occur as approximately equal numbers of males and females
which mate, females then lay eggs.
In social species, eg termites, most individuals are not sexual and
reproduction is carried out by only a small number in the colony.
Female egg-laying tubes (ovipositors may be modified for digging or
serrated for cutting leaves (to insert eggs) or used as a stinger.
EGGS ARE LAID AND HATCH LATER (oviparity)
Larvae and nymphs emerge some time after eggs are deposited.
This is the usual type of egg hatching, eg moths and butterflies.
Adult
aphid
Live
nymph
EGGS ARE LAID AND HATCH IMMEDIATELY (oviviparity)
Eggs contain fully developed larvae and nymphs which emerge
immediately after the egg is laid.
Examples include various flies and coccids.
LIVE YOUNG ARE BORN (viviparity)
Eggs mature and hatch within the female body.
Common in aphids, scales and many flies.
REPRODUCTIVE
CAPACITY
PARTHENOGENESIS
Butterfly
Bee
Aphid
INSECTS HAVE TREMENDOUS REPRODUCTIVE CAPACITY
1 pair of San Jose scale insects can produce 1 million offspring each
year!
REPRODUCTION WITHOUT. FERTILIZATION OF EGGS
Parthenogenesis may take place in any type of egg hatching (see above)
and occurs in many different types of insects.
SPORADIC
Parthenogenesis may take place only occasionally although males occur
regularly.
Male and female butterflies and moths may be produced from
unfertilized eggs.
CONSTANT
Parthenogenesis may take place regularly as a normal phenomenon, eg
in aphids, stick insects and some wasps.
Male honeybees are regularly produced from unfertilized eggs and
females from fertilized eggs.
CYCLIC
Parthenogenesis alternates with normal sexual reproduction in a regular
sequence throughout the year.
Common in aphids.
HERMAPHRODITE
COLOUR AND LIGHT
INDIVIDUALS WITH BOTH MALE AND FEMALE REPRODUCTIVE ORGANS
Individuals possess both functional male and female reproductive organs,
eg cottonycushion scale.
MATING
Colour and lights can be used to gain attention of females for mating, eg
female tropical butterflies display bright colors to attract a male.
Insects and allied pests - Biology 23