About Lesson
Families of economic importance
a. Cicadellidae: (Jassidae): Jassids or leaf hoppers
- Slender, usually tapering, posteriorly, wedge-shaped insects usually rest in a position ready for jumping.
- When disturbed they leap often several feet.
- Antennae minute, bristle-like, 3-segmented
- One or two rows of small spines are present on the hind tibia which is the most important feature.
- Both young ones and adults have the characteristic habit of running sideward or diagonally.
- These are very important vectors of viral diseases.
- The ovipositor is well developed and adopted for lacerating plant tissues for egg laying.
- Many excrete honeydew through the anus.
- Forewings are somewhat thickened and often brightly colored
- Anal veins 1A and 2A do not unite to form a ‘Y’ shaped vein. Eg: Cotton leafhopper –Amrasca biguttula biguttula Paddy leafhopper –Nephotettix virescens – Mango hoppers – Amritodes atkinsoni, Ideoscopus clypealis
b. Delphacide Plant hoppers
- This is the largest family among the plant hoppers
- Most of the species are small with reduced wings
- The characteristic feature of this family is the presence of a large mobile apical spur on the hind tibiae.
- Costal cells are absent in the winged forms
- Alary polymorphism is very common winged, wingless, and brachypterous
- Forms occur in some species. Eg Brown plant hopper of paddy (BPH)-Nilaparvata lugens
- White-backed plant hopper on rice (WBPH) –Sogatella furcifera
c. Aphididae : Aphids or plant lice
- This family constitutes a large group of small soft-bodied, pear-shaped, fragile phytophagous insects that are frequently found in large numbers sucking the sap from various parts of plants.
- Antennae fairly long
- Rostrumis usually long and well-developed
- The characteristic feature of aphids is the presence of a pair of cornicles on the dorsal surface of 5th or 6th abdominal segments (It is believed that they produce waxy substances)
- Winged / Wingless. Alary polymorphism is prevalent. When winged, hind wings are much smaller with fewer veins. At rest, the wings are generally held vertically above the body.
- Tarsus – 3 segmented with a pair of claws
- Nine pairs of lateral spiracles present
- Excrete honeydew through the anus (honeydew consists of excess sap, excess sugars, and waste materials) to which ants are attracted,
- Associated phenomena in reproduction are parthenogenesis, oviparity, and viviparity.
- Occurrence of alternation of generations. The sexes are unequally developed, males often being rare. Eg: Myzus persicae – Tobacco aphid, Aphis gossypi – Cotton aphid, Aphis craccivora – Groundnut aphid
d. Pseudococcidae Mealy bugs
- Females are wingless, elongated oval with distinct segmentation.
- Body covered with powdery wax or filamentous waxy secretions.
- Legs well developed. No instar is sessile. All the insect stages can move because of legs.
- Eggs are placed in a loose cottony waxy material.
- Eg: Brinjal mealy bug – Planococcus insolitus Citrus mealybug –Planococcus citri Sugarcane mealy bug –Saccharicoccus saccharin
e. Coccidae Scale insects (Soft scales):
- The females in this group are flattened, elongated oval insects with obscure segmentation and hard smooth exoskeletons or covered with wax or tough scales.
- They are wingless, legs present or absent and the antennae absent or much reduced.
- Males are active, 1st pair of wings well developed, 2nd pair reduced to halters.
- Tarsus if present 1 – segmented with a single claw.
- Metamorphosis complex. 1st instar nymph has legs & antennae anis d active known as the crawler after 1st molt, becomes sessile a waxy or scale-like covering is secreted.
- In males, the last instar preceding adult is quiescent and called a pupa. Females have one less instar than males.
- Oviparous, ovoviviparous
- Excrete honeydew-like aphids Eg: Pulvinaria side – Guava scale, Icerya purchase – cottony cushion scale
f. Aleurodidae E.g. White flies
- E.g.: Sugarcane whitefly – Aleurolobus barodensis Cotton whitefly –Bemisia tabaci Castor whitefly –Trialeurodes.