Agriculture Entomology Important Point
Agriculture Entomology Important Point
Reproductive System In insects male and female sexes are mostly separate.
1.Sexual dimorphism:–
- It is common where the male differ from the female morphologically.
- Example- Bee, Mosquito and Cockroach.
2.Gynandromorph:-
- (Sexual mosaic) Abnormal individual with secondary sexual characters of both male and female.
- Example- Mutant Drosophila.
3.Hermaphrodite:-
- Male and female gonads are in one organism.
- Example- Cottony cushion scale.
Types Of Reproduction:- Three types of reproduction is generally observed in Insect.
1.Oviparity:-
- Majority of female insects are oviparous that is, they lay Eggs.
- Example- Head louse moths.
2.Viviparity:-
- Unlike oviparous, here initiation of egg development take place within the mother.
- Four main types of viviparity are observed in different insect groups.
i.Ovoviviparity:-
- Thysanoptera, some cockroaches, few beetles, and some flies-(fleshfly).
- Fecundity of this group is low.
ii.Peseudoplacental Viviparity:-
- This occurs when a yolk-deficient egg develops in the genital tract of the female.
- Example- Aphids, some earwigs, psocids and polytenid bugs.
iii.Haemocoelous Viviparity:-
- This involves embryos developing free in the female’s haemolymph with nutrients taken up by osmosis.
- This form of internal parasitism occurs only in sterpsiptera and some gall midges.
iv.Adenotrophic Viviparity:-
- This occurs when a poorly developed larva hatches
- Example- Flies, louse or wallaby flies, bat flies.
3.Parthenogenesis:- Reproduction without fertilization is called parthenogenesis.
Different types of parthenogenesis are as follows
| parthenogenesis Types | Example |
| Based On Occurrence | |
| Facultative (not compulsory) | Bee. |
| Obligatory or constant (compulsory) | Stick insect |
| Cyclic or spordic | Aphid. |
| Based On Sex Produced | |
| Arrhenotoky (Produce male) | Bee. |
| Thelytoky (produce female) | Aphid. |
| Amphitoky or deuterotoky (produce both male and female) | Cynipid wasp. |
| Based On Meiosis | |
| Apodictic | No meiosis occurs |
| Automictic | Meiosis occurs, but diploidy is maintained |
Organisms are classified according to a system of seven ranks
| S.N. | Ranks (In descending arrangement) |
| 1. | Kingdom |
| 2. | Phylum |
| 3. | Class |
| 4. | Order |
| 5. | Family |
| 6. | Genus |
|
7.
|
Species |
Classification Of Class Insecta Upto Orders
- Insect is a Six legged arthropod.
- Taxonomist A.D. Imms proposed a classification of insect.
Phylum:- Arthropoda (with several classes)
Class:- Insecta (Hexapoda)
Characters of class Insecta
- Body is divided into three regions. Head, Thorax & Abdomen
- In head a pair of antenna and a pair of compound eyes are usually present.
- Thorax is the centre of locomotion with, 3 pairs of five jointed legs and Two pairs of wings.
- Excretion is mainly through malpighian tubules.
- Tracheal system of respiration well developed.
- Brain is divided into protocerebrum, deutocerebrum and tritocerebrum.
The class Insecta has two subclasses viz., Apterygota and Pterygota.
| Apterygota | Pterygota |
|
Primarily wingless evolved from wingless ancestors
|
Winged or secondarily wingless- evolved from winged ancestors. e.g. Flea, head louse, bed bug.
|
| Metamorphosis is totally absent or slight. | Present |
| Mandibular articulation in head is monocondylic i.e., single | Dicondylic i.e., double. |
| Pleural sulcus in thorax is absent. | Present |
| Pregenital abdominal appendages present. | Absent. |
The subclass Apterygota has 4 orders namely
| Orders | Word meanings | Example |
| Thysanura | Thysan- fringed, Ura-tail | Silverfish |
| Collembola | Coll- glue; Embol- peg | Springtail or snowflea |
| Protura | Pro- first, Ura- tail | Proturans or Telsontail |
| Diplura | Di- two; Ura- tail | Diplurans or Japygids |
The sub-class Pterygota has two division-
- Exopterygota
- Endopterygota
Based on the wing development.
| Character | Exopterygota | Endopterygota |
| Wing development | External | Internal |
| Type of metamorphosis | Incomplete(Hemimetabola) or gradual (Pau- rametabola) | Complete (Holome- tabola) |
| Pupal stage | Absent | Present |
| Immature stage | Naiad or Nymph | Larva |
| No. of orders | 16 | 9 |
The Class Insecta has 29 orders (4 in Apterygota and 25 in Pterygota)
| Exopterygota Groups | |
| Paleopteran orders | |
| Ephemeroptera | Mayflies |
| Odonata | Dragonfly, Damselfly |
| Orthopteroid orders | |
| Plecoptera | Stonefly Group |
| Grlloblatodia | Rock crawlers |
| Orthoptera |
Grasshopper, locust, cricket, mole cricket
|
| Phasmida | Stick insect, leaf insect |
| Dermaptera | Earwigs |
| Embioptera | Webspinners /Embids |
| Dictyoptera |
Cockroach, preying mantis
|
| Isoptera | Termites |
| Zoraptera | Zorapterans |
| Hemipteroid orders | |
| Psocoptera | Book lice Group |
| Mallophaga | Bird lice |
| Siphonculata |
Head and body louse
|
| Hemiptera | Bugs |
| Thysanoptera | Thrips |
| Endopterygota | |
| Panorpoid complex | |
| Neuroptera | Antilions, aphidlion, owl flies, mantispid flies. |
| Mecoptera | Scorpionflies. Group |
| Lepidoptera | Butterflies and moths. |
| Trichoptera | Caddisfly |
| Diptera | True fly. |
| Siphonaptera | Fleas. |
| Others | |
| Hymenoptera | Bees, wasps, ants. |
| Coleoptera | Beetles and weevils. |
| Strepsiptera | Stylopids |
Agriculture Entomology Important Point
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