Identifying Insects and Understanding their Behavior and Life Cycles

5.4.1. Based on their feeding habits, majorly they can be divided into two groups:

i. Biting and chewing insects – insects which have their food by biting and chewing. E.g. Caterpillars, Helicoverpa, Beetles, Bugs, Slugs, Snails, etc.

Fig 1. Biting and Chewing Insects

ii. Sucking and Piercing insects – The insects which have their food by sucking the plant sap using their strong mouthparts called E.g. Aphids, Cotton Strainers, Mealy bugs, Scale Insects, Capsids, White flies, etc.

Fig.2. Sucking and Piercing Insects

5.4.2. Based on the damaged symptoms, majorly they can be divided into following groups:

i. Borers – They bore into the plant part and feed on the material. Based on the part they damage, they are variously known as – stem borers, fruit borers or shoot borers.

Fig.3. Borers

ii. Leaf Miners – Generally they mine into the layers of leaf and feed on the chlorophyll.

Fig.4. Leaf Miners

iii. Leaf Skeletonizers – the insects feed on the leaves leaving the veins with which the leaves appear skeletonized i.e. only veins are seen, and all the green matter is eaten away.

Fig.5. Leaf Skeletonizers

iv. Defoliators – Insects that feed on leaves are called defoliators. In severe cases complete defoliation occurs.

Fig.6. Defoliators

v. Gall Makers – Due to their feeding action, certain insects bring in structural changes in the host plant.

Fig.7. Gall Makers

5.4.3. Based on their appearance, majorly they can be divided into following groups:

i. Moths and Butterflies: This group is known for their colorful wings with various patterns. They have 4 stages in their life cycle: egg, larva, pupa and adult. The adults have the colorful wings. The larvae too come in various colors. This group has more pests of crops. Most of the borers (fruit borer, stem borer, shoot borer etc.) come under this group. Butterflies are mostly harmless except a few like blue butterfly, sulphid butterflies (on Cole crops) and pomegranate butterfly. Butterflies’ larvae feed on weeds mostly.

Fig.8. Adult butterflies and moths

The difference between moths and butterflies are –

• While in resting position butterflies keep their wings folded up, perpendicular to the surface while
  the moths rest parallel to the surface (like asbestos roof).
• Mostly butterflies are diurnal (day time active) and moths are nocturnal (evening/night time active).
• Mostly moths are crop pests and very few butterflies are crop pests.

Fig.9. Young ones of  butterflies and moths

ii. Bees and Wasps: This group has most of the agriculturally beneficial insects i.e. parasitoids. Egg, larval and pupal parasitoids are there. These insects can be identified by their thin waist and sharp ovipositor (last segment of the abdomen). Ants, bees, wasps etc. come under this category. Very few pests are there under this group (mustard saw fly).

Fig.10. Bees and wasps

5.4.4. Insect Life Cycle:

Insects have four stages in their life cycle. They are – egg, larva, pupa and adult. Based on the life cycle insects are divided into:

i. Insects with a complete life cycle: Insects in which all 4 stages are present. For e.g. butterflies, moth

ii. Insects with an incomplete life cycle: The insects in which one or more stages are not present. This usually consists of egg, nymph and an adult. The young ones resemble their parents/adults except for the wings (i.e. they cannot fly). The food habits are similar and sometimes can be different than the adults. Ex: A Bug