Biological relationships Insect Predators
Host-predator Relationships:
1) On the Basis of Type of Feeding (type of mouth parts):
a) Chewing Mouth Part:
The prey is consumed with use of chewing type of mouth parts, e.g. preying mantids, ants, coccinelids, ground beetle, lady bird beeltles, carabids. They simply chew up and bolt down there victims – legs, bristles, antennae and all.
b) Sucking Mouth Parts:
The predator feeds on their prey by sucking the juice from body, e.g. Assassin bug, Reduviidae, lacewing larvae. Chrysopidae, Syrphidae, Prentatomids. These insect often injects a powerful toxin which quickly immobilizes the prey so that the feeding process is placid affair with little thrashing about by the victim. For example once a lacewing larvae clamps its sickle mandibles into a caterpillar several time its size, the caterpillar is doomed and its period of struggle lasts but a few seconds.
2) On the Basis of the Specificity of Host Relations:
Thompson (1951) referred to the fact that predators have a full complement of sense organs and can perceive their prey at a distance. There was a high degree of host specificity. The importance of olfactory response and visual stimuli prey location is also elaborated.
a) Monophagous:
The predator which is highly host specific and consume exclusive on a single species of prey, e.g. Rodolia cardinalis is a specific predator of cottony cushion scale (Icerya purchasl).
b) Oligophagous:
The predators with restricted host range feeding on more than one host preys of the closely related species, e.g. Syrphid larvae feed only on aphid species.
c) Polyphagous:
The predator’s species feed on a wide a range of prey, e.g. preying mantids, Prentatomids, ants, ground beetles etc.
3) On the Basis of Morphological Adaptations:-
Many species have special morphological or biological adaptations to make them effective.
a) Preying Mantids:
They have grasping and holding forelegs as well as large eyes and on extremely mobile head to assist in location and capture their prey.
b) Dragon Flies:
Larval dragon flies have specialized mouth parts to capture aquatic prey and adult dragon flies are excellent fliers and able to catch their prey on the wing.
c) Adult Carabid Beetles:
They have long legs, move rapidly to run down their prey.
d) Ant Lion:
Larvae settle in their specially constructed pits awaiting on unsuspecting prey.
e) Ants:
They utilizing their social habits assist each other in capturing and moving prey to their nests.
f) Wasps:
They often paralyze their prey with a venomous sting and provides food for their developing brood.
g) Syrphid Flies:
Adults may deposit their eggs directly among aphids so that food is immediately available to newly maggots.
h) Coccinellid Beetle:
The hemispherical shape and slow movement in a colony of their prey do not disturb the feeding ants and allow the predators to continue feeding. e.g. lady bird beetle.
i) Stink Bugs:
With their powerful sucking mouth parts they are able to withdraw body fluids from their prey while it is suspended in the air.
On the Basis of Competition within and Between Predator Groups:
Cannibalism:
It occurs when on species fees on others of its own kind. This rarely occurs in nature, but it would have an advantage for species survival in the absence of alternate food. Under laboratory condition of crowding and limited food supply cannibalism can occur readily. Some coccinellids just after emerging from their eggs may feed on unhatched eggs in the same cluster Lacewings utilize stacked eggs to prevent such cannibalism or perdition by other species.