Insect Biology: Classification, Reproduction, and Pest Management
Insect Classification
Apterygota: Wingless insects without metamorphosis, or with very slight metamorphosis. Their abdomen has appendages in addition to the cerci and those within the genitalia.
Pterygota: Winged insects, or wingless with some more or less complicated metamorphosis. Their abdomen is without appendages, in addition to the cerci and the genitalia.
Insect Reproduction and Population Dynamics
Biotic potential is the ability of an insect to multiply without any countervailing force decreasing the power of multiplication. It depends on two factors: the multiplication rate and the proportion of individuals of each sex, or sex ratio, occurring in each generation.
Fertility is one of the basic data points to determine the biotic potential of insects. It varies between very wide limits, from a few eggs laid by some wasps to the hundreds of thousands produced by termites. Another component is the length of their cycle and growth rate.
In nature, there is rarely the same number of females as males in a particular species. Sexual reproduction is normal among insects, but often there is total parthenogenesis.
Resistance to the environment is the set of factors that contribute in a given ecosystem to reduce the multiplication of the insect and thus slow the development of the population. These factors may be physical (abiotic) or biological (biotic).
Abiotic factors include light, temperature, humidity, and air movement.
Ecological Interactions
Parasitism is the action exercised by organisms living in or on a host organism of a different species from which they draw sustenance.
Predation is the action exerted by free-living organisms that kill their prey quickly to catch them.
Biological equilibrium: Under normal conditions, there are a number of insects that live off the trees without their number constituting a threat. They reach a mass that remains below critical levels. Thus, we have the coexistence of trees and insects without endangering the existence of any species. In this case, the biological balance is in equilibrium.
Impacts and Management
Tolerance is what something is capable of withstanding, depending on the body and the force.
Losses:
- Direct: Loss of wood product
- Indirect: Loss of recreational areas, allergies
- Socio-economic: Closure of factories in the absence of good wood
IPM Benefits:
- Reducing the amount of pesticide used
- Conservation of natural enemies of pests
- Lower total cost of fighting pests
Contact insecticide should be applied in such a manner and at such a time that we are sure that the pest cannot avoid direct contact with the product.
Ingestion insecticide acts when ingested by the insect.
Inhalation insecticide gases or vapors are entering the insect through the spiracles of the respiratory system.
Insecticide Types
First-generation Insecticides: Calcium, lead, sulfur, and nicotine.
Second-generation Insecticides:
- Organochlorines (OCs): Act simultaneously by contact and ingestion. They are quite persistent, have chronic toxicity, and their broad spectrum of action may lead to adverse side effects. Many of them are prohibited.
- Organophosphates: Act by contact, inhalation, and intake, separately or simultaneously. Their persistence is scarce, and they have acute toxicity. Malathion has high toxicity, while Fenthion has low toxicity to humans.
- Carbamates: Can act through the three pathways. They have low persistence and low toxicity but are highly toxic to bees.
Key Terms
Emergence: The birth of the adult insect (in inverted commas because there is really no such birth). The adult stage is the last phase of development of the individual.
Endemic: A plague is said to be endemic in an area where its more or less intense attacks are repeated year after year. An animal or plant is endemic in an area where it is typical or unique.
Epidemic: A plague that appears sporadically in an area is considered epidemic when extraordinary virulence appears occasionally, and after a relatively short period, attacks become minimal levels again, just for the conservation of the species in that area.
Fertility: The number of eggs laid by a female.
Potandria: In the period of emergence of adults, potandria is said to occur when males emerge earlier than females. This is a very common phenomenon among insects.