MIDLANDS STATE UNIVERSITY
FACULTY OF SCIENCE AND TECHNOLOGY
DEPARTMENT OF BIOLOGICAL SCIENCES
Name : Panashe Noel Mahati
Reg : R124982N
Level : 4.2
Module : Entomology
Lecturer : Mr Bare
Describe the life history strategies displayed by agricultural insect pests and discuss their implications for pest management.
D. Ludwig and L. Rowe (1990), Short-term foraging behaviour is typically influenced by the needs to obtain food at a high rate and to avoid predation. There is increasing evidence that the need to balance these conflicting demands plays a role in ontogenetic habitat shifts, including the shifting characteristic of complex life cycles. The most systematic way of dividing up the insect world is separating them into those that have an incomplete metamorphosis and those that have a complete metamorphosis. These are known as hemimetabolous and holometabolous insects respectively.
This differentiating aspect is the degree of metamorphosis the insect undergoes from an egg to an adult. All insect life cycles start with an egg, and end with an adult insect, it is only the path between these two points that makes the difference. The distinguishing factors between the two forms of life cycle are whether the pupa is present.
Hemimetabolous life cycles have 3 stages: an egg; nymph (usually several moults); adult.
Holometabolous life cycles have 4 stages: an egg; larva; Pupa; adult.
A pupa is a special resting, normally unmoving stage of an insect’s life. During this stage it undergoes a physical transformation from a bag with a mouth at one end into a complex adult insect. This is the consequent of metamorphosis. (Brodsky, 1996)
Hemimetabolous insects, with an incomplete metamorphosis have no pupa and their wings develop on the outside of their body. Wing buds grow outside cuticle at each moult and at final nymphal moult it gains genitalia and fully grown wings as an adult. Their growth is largely direct, undergoing...