Advantages and Disadvantages of Cannibalism in Insects
Advantages:
We have now seen that there are different types of cannibalism that occur for different reasons in insects, but ultimately, they all provide some sort of advantage to either the individual or the individuals offspring. Although the advantages associated with sexual, density dependent and egg, and young cannibalism are not the only advantages associated with cannibalism in insects. Here we take a closer look at some of these advantages, which can help give us a deeper understanding for why cannibalism may have evolved in such a diverse group of organisms.
First off cannibalism provides a nutritious dinner to the consumer, but through the process of deleting an individual from the population, cannibalism is able to regulate population density and decrease intraspecific competition in a population (Richardson et al, 2010). Intraspecific competition can be described as the competition between individuals of the same species for limited resources (Towsend et al, 2009). In turn it is easy to understand that cannibalism in a population can increase the fitness of individuals by reducing the amount of competition there is for resources such as: food, habitat and mates.
First off cannibalism provides a nutritious dinner to the consumer, but through the process of deleting an individual from the population, cannibalism is able to regulate population density and decrease intraspecific competition in a population (Richardson et al, 2010). Intraspecific competition can be described as the competition between individuals of the same species for limited resources (Towsend et al, 2009). In turn it is easy to understand that cannibalism in a population can increase the fitness of individuals by reducing the amount of competition there is for resources such as: food, habitat and mates.
Figure 10 : Intraspecific Competiton
Not only does cannibalism help to reduce the intraspecifc competition in a population, it also helps to remove parasitized (Figure: )and diseased individuals from the population (Richardson et al, 2010). Just like in a human population disease and parasites can spread in insect populations, which can lead to a reduction in their fitness and sometimes even death. Unlike humans, insects don't have the medicines and antibiotics that are so readily available to us, so they have opted for a better solution which involves the consumption of the sick individual. This provides them with nutrition and also helps to reduce the risk of an infection spreading to other members of the population.
Figure 11 : Nematodes emerging from a wax moth larvae.
As we have now seen, there are numerous advantages that come with cannibalism, but the advantages associated with cannibalism can also be species specific, meaning that some species may benefit from cannibalism in different ways than others. Church and Sherratt (1996) found that under low food conditions larvae which had the opportunity to cannibalise survived significantly longer than larvae which did not. Another example is seen in the sexual cannibalism that occurs in mantids. Barry et al (2007) along with many other studies have highlighted the benefit associated with the consumption of the male mantid by the female after copulation. Specifically the work conducted by Barry et al (2007) found that cannabilistic females greatly improved their body condition and as a result were able to produce heavier egg cases than their non cannibalistic equivalent. In turn the nutritional gain associated with male consumption has the potential to greatly increase the fecundity of the female.
As we have now seen, there are numerous advantages that come with cannibalism, but the advantages associated with cannibalism can also be species specific, meaning that some species may benefit from cannibalism in different ways than others. Church and Sherratt (1996) found that under low food conditions larvae which had the opportunity to cannibalise survived significantly longer than larvae which did not. Another example is seen in the sexual cannibalism that occurs in mantids. Barry et al (2007) along with many other studies have highlighted the benefit associated with the consumption of the male mantid by the female after copulation. Specifically the work conducted by Barry et al (2007) found that cannabilistic females greatly improved their body condition and as a result were able to produce heavier egg cases than their non cannibalistic equivalent. In turn the nutritional gain associated with male consumption has the potential to greatly increase the fecundity of the female.
Evolution:
The advantages associated with cannibalism may give us an insight into why it evolved and also why it is so prevalent in insects. So far we have seen that cannibalism as a whole provides insects with a fitness advantage, as it has the potential to reduce the risk of infection within a population, reduce intraspecific competition, increase the survival and fecundity of the cannibal and improve their overall body condition. These are all reasons to help understand why cannibalism evolved, but having said that, there are disadvantages associated with cannibalism. Although for cannibalism to have evolved and become so prevalent amongst such a diverse group like the insects, the advantages must have outweighed the disadvantages.
Disadvantages:
We mentioned above that cannibalism can be advantageous for the fact that it can remove disease and parasites from a population, but what happens when the consumption of a diseased individual results in the acquisition of said disease or parasite? Well, the transfer of pathogens from the victim to the cannibal is possible and could result in the death of the cannibalistic individual (Richardson et al, 2010). Cannibals also face the risk of injury or death when attempting to capture their prey, but this risk is usually minimized by the fact that insects tend to prey on individuals smaller than them (Capinera,
2008). There is also the instance of removing potential mates from the population, and reducing the group size which can make the individual more vulnerable to predation(Capinera, 2008).
Figure 12: Dead Insect
There is also the instance of removing potential mates from the population, and reducing the group size which can make the individual more vulnerable to predation (Capinera, 2008).
There is also the instance of removing potential mates from the population, and reducing the group size which can make the individual more vulnerable to predation (Capinera, 2008).
Figure 13 : Lonely Insect