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AR - 7916 B.Sc. (Forestry) (Sixth Semester) Examination

Paper-IV : Forest Entomology Time : Three hours

Maximum Marks : 60

Model answer

DR. PRABAL SARKAR Department of Forestry, Wildlife & Environmental Sciences

Guru Ghasidas Vishwavidyalaya

Bilaspur, Chhattisgarh

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AR - 7916 B.Sc. (Forestry) (Sixth Semester) Examination

Paper-IV : Forest Entomology Time : Three hours

Maximum Marks : 60

Note : Section-A is compulsory. Attempt any four questions from Section-B

Section: A

1. Objective type questions (20x1=20)

Short questions:-

(i) What is insect pest?

Ans : Insect which ruthlessly damages our property (Agriculture, livestock, household articles) and

causes severe economic loss and public health is called insect pest.

(ii) What is called to those insect whose mouth parts pointed forward?

Ans : Prognathus.

(iii) Who authored the book entitled the Fauna of British India series on “Moth of India” published in 1892?

Ans : Sir G. Hampson.

(iv) What are the different segments in insect thorax?

Ans : Three segments- namely pro, meso and meta thorax.

(v) How many divisions are there in insect legs?

Ans : Five.

(vi) What is insect spiracle?

Ans : Spiracle is a small hole of some animals that serves respiration.

(vii) What do you mean by a hyperparasitism?

Ans : The parasite is being parasitized naturally by another species of parasite is called

hyperparasitism.

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(viii) How much relative humidity should be managed before storing of forest seeds?

Ans : 70-75%.

(ix) What are the major insect pests of nursery plants?

Ans : Cutworms, white-grubs, termite, crickets, grasshopper etc.

(x) How many insect pest causes damage to teak?

Ans : More than 174 species of insect pests.

Fill in the blanks :-

(xi) _J. G. Koening , a Danish physician turned Naturalist published first detailed life history of termites of India.

(xii) The Indian Ants is the first publication on biological control of Insect Pests in India authored

by _Rothney_ in 1893.

(xiii) The mouthparts of Insect which has a long finger like extension that tends to fold back while

in rest is called _Opisthognathus_ .

(xiv) All insects except the __protura_ possess a pair of antennae.

(xv) Abdomen of insect is differ from head and thorax by lacking of __appendages_ .

(xvi) Fumigants effect on _metabolic process_ and _acts as neurotoxicants_.

(xvii) Pests which are being parasitized by different species of parasite are called _multiple parasitism_.

(xviii) _Pyrethrum insecticide is extracted from flower of the plant, Chrysanthemum

cinerariaefolium.

(xix) In India, the Insecticides Act has been enforced in the year _1971_.

(xx) The exoskeleton in insect is made up of _chitin_.

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Section : B (Attempt any four questions)

Q2. Define metamorphosis? What are the different types of metamorphosis found in insect? How

does it differ from growth? (2+6+2)

Ans :

Definition :

Whenever the development of an embryo into adult takes place through a series of successive

transitional, morphologically alike or variable forms, such types of mode of post-embryonic

development is called metamorphosis. It is in other words, the process of indirect development of an

embryo into adult.

Different types of metamorphosis

Depending upon the degree of changes, three different types of metamorphosis is recognized which

are given below :-

(a) Ametamorphosis :

It is also known as no metamorphosis. It is common in some primitive Apterygote insect in which

there is no change or very little change takes place. The young/ immature insect looks similar to

their adult insect except in body size and shape and sexual maturity. The only polyembryonic

development takes place in instars of several abdomen segments. Eg. Starfish

(b) Hemimetamorphsis :

It is the kind of incomplete metamorphosis. In some insect the incomplete metamorphosis takes

place through partial or gradual metamorphosis, during which the immature nymphs become the

imago by development of external wing-buds into perfect wings and thus showing the exopterygote

condition. There are two different kinds of hemimetamorphosis which are as follows –

(i) Paleometabolous – In this type of metamorphosis, the young immature insect (nymph)

differ from their adult paleogenetically. Eg. Protura.

(ii) Heterometabolous – In this type of metamorphosis, the nymph differ from their adult

coneogenetically. Eg. Odonta.

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(c) Holometamorphosis :

In this type of metamorphosis, a complete or indirect metamorphosis can be seen. The larva quits

the egg at very early stage of morphological development. The wings develop as bud which are

internal. Eg. Lepidoptera.

Difference from growth

Metamorphosis is differing from the growth of insect because growth involves both embryonic and

post-embryonic development, while the metamorphosis involves only post-embryonic development.

In case of metamorphosis, the shape of every stage (larva, pupa and adult) is different from each

other while in growth no major difference can be seen except shape and size.

Q3. Write short notes on – (5+5)

(a) Different types of insect antennae.

The insect head is characterized by possessing a single pair of antennae. The antennaes are the

homologous with the antennules of the crustaceans. The antennae are segmented and mobile paired

structure. They are basically fixed into the deep antennal socket.

The antennae are known to be present in Protura and also in larvae of most Hymentoptera.

Types of antennae :

There are thirteen types of antennae which are as follows

(a) Setaceous Antennae

The flagellum looks like a bristle due to gradual reduction in the size of the segment. Eg. Odonta.

(b) Filiform Antennae

The flagellum appears as a thread like structure made up of uniformly thin segments. Eg. Blatidae.

(c) Moniliform Antennae

The flagellum is composed of the globose-shaped segment, providing a necklace-like appreance to

the entire antennae. Eg. Termites.

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(d) Serrate Antennae

The flagellum consists of triangular segment with eccentric arrangement leaving free ends of the

segments . Eg. Elatridae.

(e) Pectinate Antennae

The flagellum is extended on only one side and look like a comb. Eg. Bombycoidea.

(f) Clavate Antennae

The successive segments of the flagellum become a club-shaped form. Eg. Some Lepidoptera.

(g) Capitate Antennae

The proximal segments of the flagellum are uniform sized while the distal segments modify into a

large knob. Eg. Nutidulidae.

(h) Lamellate Antennae

The terminal segments of the flagellum modify into the leaf-like broad plates. Eg. Melolontha.

(i) Geniculate Antennae

The antennae are bent completely from the scape-pedicel joint. Eg. Chalcidoidea.

(j) Plumose Antennae

The flagellum is composed of large number of cylindrical segments and the segments are provided

with long hairs on either side. Eg. Male mosquito.

(k) Pilose Antennae

The flagellum looks like a flexible hair. Eg. Female mosquito.

(l) Aristate Antennae

The flagellum is undivided but the second segment is situated at the different angle on the first

segment.

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(m) Stylate Antennae

The segmented antennae and third segment divides repeatedly and thus it becomes falsely multi-

segmented often forming a stylate.

Fig-Different types of antennae

(A) Typical, (B) Filliform, (C) Setaceous, (D) Moniliform, (E) Serrate, (F) Clavate, (G) Plumose,

(H) Aristate, (I) Stylate, (J) Pectinate, (K) Capitate, (L) Lamellate, (M) Flabellate, and (N)

Geniculate.

(b) Typical mandible mouthparts

Ans :

The mandibulate mouthparts are considered to be the primitive form. They typically consists of

following parts :-

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(a) Labrum : Typically this is a movable flap hanging down from the edge of the clypeus and

covering the mouth. Its inner side forms the front of the pre-oral cavity and is called the

epipharynx.

(b) Hypopharynx : It is an unsegmented outgrowth of the body wall and lies in the pre-oral cavity

like a tongue.

(c) Mandible : They are paired appendages of fourth head segment behind the mouth and highly

sclerotized unsegmented jaws.

(d) Maxillae : The maxillae lie directly behind the mandibles and are the paired appendages of fifth

head segment and serve as accessory jaws, helping in holding and chewing food. Each maxillae

is composed of five different parts namely, Cardo, Stipes, Galea, Lacinia and Palpes.

(e) Labium : The labium or the lower lip, is the most posterior part of the mouthparts and more or

less similar in structure as the maxillae but with appendages fused along the midline and

forming a large plate like structure on the ventral side of the head. It is composed of two parts,

viz., anterior prementum and a larger posterior postmentum, the two being separatd by a

traverse labial suture. The prementum carries distally paired ligula, each member of which is

further divided into an inner glossa and an outer paraglossa. The lateral part is projected into a

palpiger, each carrying jointed palpi.

Figure-Typical mandible mouthparts (Cockroach)

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Q4. What are the major insect pests of forest nursery? Write details about the damage pattern of

White –grubs and Cutworm. Brief about their management practices. (2+5+3)

Ans : The nursery stock, being tender and delicate, is prone to damage by various biological pest.

Major injury to nursery stock is caused by certain groups of insect, such as white-grubs, cutworms,

termites and crickets, all classified as “Major Pests”. Many other insects, which include defoliators,

sapsuckers etc. cause minor damage to nursery stock.

Damage pattern

(a) White-grub :

White-grub is also known as “The Chafer Beetle”. They cause severe damage in the nursery plants.

Egg - A single female beetle may lay nearly 30-60 eggs which transform into larval stage during

summer after 4-6 week of first sower.

Larvae – There are three larval instars, each lasting for nearly two to ten weeks, but the last instar

may last for 3-6 moths. The second and third instar larvae go down in search of live root.

Pupa – The grub undergoes pupation usually during winter months from November to January.

They move down deeper in the soil and construct a pupal cell.

Adult- Adult beetle emerge out between November and January. The beetles emerge from the soil

in the evening, usually between 7 and 8 pm in summer from April to June. Both the sexes

congregate on their host plant and remain active throughout the night. They continue to feed on the

foliage of the host plant. Many species of beetle have also been recorded attacking roots of

seedlings in forest nurseries in the Indian sub-continent. Dying off in nursery stock usually occurs

as a result of root injury by the root-feeding white-grub larvae (species of Granida).

(b) Cutworms :

Four species of cutworms are seems to be the major pest for nursery plants.

Egg- Oviposition takes place at the time of evening. The female moth continues to lay eggs almost

throughout the night. They lay about 2000 eggs in small batches on ground litter.

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Larva – Hatching takes place after 2 days in summer to about seven or eight days in winter. The

larva undergoes 6 to 7 moults, except the last one when the larva is ready to undergo pupation.

Total larval period varies from 20 to 35 days.

Pupation- Pupation occurs underground in a specially prepared chamber of earth. The pupal period

varies from 10 days in summer to nearly 30 days in winter.

Adult- Moth emerges by brust opening the obtuse end of the pupa. Newly emerged moth possesses

soft and crumpled wings which expand and harden very soon.

They are considered to be the most serious pest in regeneration areas in the coniferous forests. The

larvae cut off young germinating seedlings in thousands in seed beds and patches of deodar, wasting

a large chunk of the growing stock, consuming only a fraction of the cut plants.

Management :

There are various methods by which cutworm and white grubs can be controlled at the nursery. A

few of these control measures are given below :

- Eradication or removal of the seedling infested with the pest.

- Hand picking or mechanical method of collection and killing at the time of infestation.

- Use of Silvicultural technique to control their population. Deep ploughing may lower the

chances of infestation.

- Use of pheromones.

- Use of some parasite as a part of biological control of these pests.

- Spraying of endosulfan and other pesticide to control pest on emergency basis.

Q5. Write short note on- (5+5)

(a) Oviposition

Ans : Egg laying (Oviposition) usually commences only sometimes after the copulation. The

interval (i.e. between the copulation and the oviposition) is referred to as pre-oviposition period.

This period may be as brief as only a few minutes in short-lived insect, where the female starts

laying eggs almost immediately after copulation. In some insect (termite), where the queen may

sometimes live well over thirty years, the partners continue to copulate at regular intervals, while in

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few other cases (honey bees), the female may live as long as five years, but mating occurs only once

during the nuptial flight.

Most insect lack parental care, the females paying little attention after oviposition, leaving the

young insects to take care themselves after hatching. The eggs are therefore, generally oviposited in

sites most suitable for their survival and also where the new young insects can have ready access to

the suitable food.

In contrast to the above mentioned pattern of oviposition, certain insects, such as cockroaches lay

eggs in capsule-like structure, called Ootheca and displayed often in conspicuous places, often

glued to small twigs or walls and other such substrata.

(b) Eclosion (Hatching)

Ans : With the completion of embryonic development, the young insect (larva/ nymph) makes its

way out by rupturing the egg-shell, the chorion, at a predetermined weak spot with the aid of

various hatching structures, which facilitate breaking off shell. These structures may be in the form

of paired or unpaired strongly sclerotized processes or spines on the ventral sides of the embryonal

cuticle, frons, mouthparts or thorax of the young larvae. In most of the Hemiptera, it may be in the

form of cap-like circular disc.

Mosquito possess a spine like structure on the head which helps in piercing the egg shell, while in

some insects, rupturing of the egg shell is achieved by the application of internal pressure at one

week point by the embryo by swallowing fluid or air.

Q6. Write about the characteristics features of Insect order-Lepidoptera. Differentiate between

sub-order Rhopalocera and Heterocera. (5+5)

Characteristics

1. Head : Small, spherical and hypognathous

2. Antennae : Long but variable length, often clavate, pectinate.

3. Eye : Compound eyes-large, globular;

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4. Ocelli : Lateral, concealed under scales, situated closely ventral to eyes.

5. Mouthparts : Siphoning types with long coiled proboscis

6. Thorax : Thoracic segments fused but mesothorax is large and distinct.

7. Wings : Two pairs. Forewings large while hind wings small

8. Legs : Foreleg reduced, long and immovable.

9. Abdomen : Slender or tubular, 10 segmented

10. Male genitalia : Median saccus on the 9th

segment, penis -funnel.

11. Female organ : 9th

and 10th

segments from telescopic ovipositor.

12. Metamorphosis- complex

13. Medium to large-sized flying terrestrial insects

14. Example – Butterflies, Moths.

Characters Rhopalecera Heterocera

1. Antennae Clubbed or dilated, never

pectinate

Pectinate, plumose in males.

2. Ocelli Absent Mostly present

3. Mandibles Absent Reduced.

4. Frenulum Wanting Present.

5. Humeral lobes of hind

wings

Greatly developed Undeveloped

6. Wings at rest Folded vertically upward Held roof-like transversely

over dorsum.

7. Coupling apparatus Amplexiform type (simple

overlapping among hind and

forewings)

Frenate-type predominant.

8. Cu2 vein of forewings Wanting Present

9. Abdomen Comparatively small Large

10. Pupa Naked, coloured and supported

by silken girdles.

Within cocoon.

11. Members Butterflies Moths.

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Q7. Write details about various insect pests of sal and mention their damage pattern and control

measures. (10)

Ans :

1. Sal Cockchafer Lachnosterna

Distribution :

UP, MP, Chhattisgarh, Maharastra, Bihar and J&K.

Life Cycle :

Beetle is elongate, smooth, dark brown, about 16 mm longs and 8 mm broad. Head small, antennae

ten segmented. Larvae are 25 cm long, white and curved.

Beetle appears in the month of May in the sal forests. Female lays eggs in May and June. Larvae

feed in soil on the roots of the sal tree. The grubs feed the bark of the younger roots and also

girdling the root till late April. It pupates for a long period of three to four weeks. Mature adults

come out from soil through the humus and dead leaves above. It passes through one life cycle

during a year.

Damage :

It is a serious pest in the sal forests of Indian sub-continent. It causes heavy destruction of the young

root system and inhibiting growth of the young trees.

Control measures:

i) Burning of all the undergrowth and young trees

ii) Removal of dead leaves, humus and upper layer of soil

iii) Mechanical killing of grubs and adult beetles.

2. Sal defoliator (Lymantria dispar, L. obfuscate)

Distribution:

The Gypsy moths (Lymantria obfuscate) is distributed in Kashmir and North-Western Himalayan

region.

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Life Cycle :

The adult moths during June-July. The female moths are unable to fly and live for a short span of

two weeks and rest on the bark of the tree trunk. The fertilized female lays about a mass of 100 and

250-500 eggs which hatch in early April of the next year. The larval period lasts for 70-80 days. In

June-July, fully grown larvae undergo pupation for two weeks. The pupa is dark-brown and 20-

30mm long with fine bundle of hairs and hook-like structures on caudal end. The adult emerges in

June-July.

Damage :

The first instar larvae feed on young leaves and excavate small holes, whereas large caterpillars

feed on leaves, bud, flowers, annual shoots voraciously for a long period of six weeks. This pest is

very harmful because it often attacks a large irregular area and spreads continuously over three or

four years.

Control measures:

i) The pest can be controlled by removing egg masses from shoots of the tree during winter.

ii) By using Gyptol pheromones traps during monsoon season, adult can be collected and

killed effectively.

iii) Aerial spraying with 3% crude oil or 1% malathion on caterpillars and pupae lying on

trunks and branches in May-June.

3. Sal Hard Wood Borer (Hoplocerambyx spinicornis)

Distribution:

It is distributed from Philippines and Borneo-Sumatra to the Indian Sub-continent, Nepal and South

Afganisthan. In India, it is common in Assam, Bihar, Jharkhand, UP, Chhattisgarh, Himachal, MP,

Maharastra and West Bengal.

Life Cycle:

The adult beetles appear with beginning of monsoon. After a week since first pairing, the female

lays about 400-500 eggs in cracks, holes, flakes of bark, branches etc. The eggs hatch after 3-7 days

of incubation during June –August. The first instar larva starts making tunnel in in bark of a living

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tree with the help of strong mandibles. The larval stage last for 6-10 months from July to April next

year. The last instar larva excavates a “pupal chamber with an adult exit hole” and then pupate.

Pupation comprises a period of about 1-4 months during March – June and adults emerge out.

Damage :

Grubs initially feed under the bark, then on sap wood and finally the fully grown grubs bore into the

heartwood into tunnels. Due to vigorous tunneling the bark, phloem, sapwood and heartwood of the

tree, they cut the transport of water and nutrients causing death of the tree and also spoil the quality

of wood leading the heavy commercial loss.

Control Measures :

i) The felling and removing of the infested trees.

ii) Burning the felling refuse and live stumps

iii) Borer can be killed by pouring insecticides like endosulfan.

iv) The larvae of the click beetle can be used to control Sal Wood Borer.

Q8. What do you mean by Silvicultural method of pest control? Brief about various Silvicltural

method of pest control. Write details about the advantage and disadvantage of Silvicultural

method. (2+5+3)

Ans :

Silvicultural measure is a kind of routine farm exercise by which pests can be controlled. In this

method, farmers require the knowledge of the type of pest, their life cycle, favorable environmental

conditions and habit and their period of attack.

Various Silvicltural method of pest control

(a) Clean cultivation:

The pest generally hides themselves inside the crop residue, weed and trash after the crop is

harvested (eg. Gandhi bug). During winter season, several insect pests may hide under surface trash

and formed from dry leaves, dead vegetables or dense grasses. Eg. Codling moths, Aspara beetles.

After harvesting, the entire area can be either cleaned or fired to control pests.

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(b) Tilling the soil :

Several insect pest species undergo winter hibernation below the soil. By deep and frequent

ploughing should be done. A regular cracking of soil a will prevent the multiplication of cutworms.

By rolling the soil, the water level may be increased that drive some of the insect pests.

(c) Crop rotation :

Some pests develops host-specificity very strictly. This is because of a regular sowing of the same

species year after year. This can be restricted by a regular crop rotation. Eg. Cabbage yellow.

(d) Synchronization of sowing and harvesting :

Many pests are seasonal. They occur in a particular season or time of the year. If the sowing or

harvesting time is changed, the crop can be saved. Eg. Wheatfly, Pea stem borer etc.

(e) Use of resistant varieties

A new strain which is developed after intercrossing is found to be more resistant tom pest. By

introducing such variety, the pest-host relationship is disturbed (suitability to take protection, food

and shelter). Eg. Rough texture or surface of the soybean plant, the pest cotton and red clover

become unsuitable for attack.

(f) Use of manures and fertilizers

Manure containing nitrogen encourages attack of potato blight. On the other hand, manure

containing potassium and phosphorous reduces the chance of attack from some pests. Eg.

Wireworm and stem sawfly.

(g) Cultivation of trap crops

Trap crop is generally used to ward off the insect from the main crop. Trap crop are more attractive

and susceptible than the main crop. The planting of trap crop is done in such a time that it

susceptible stage coincides with peak activity of the insect.

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(g) Crop pruning

Pruning off the apical part of the young leaves or dead branches during initiation of infestation are

found to be suitable for pest control.

(h) Water management

Water can be used directly for suffocating insects or indirectly by changing the overall health of the

plants. This can be practiced at the time of dry season.

Advantages :

1. Cheaper compare to chemical measures.

2. Environment friendly.

3. Naturally developed control measures.

Disadvantages :

1. Time taking procedure.

2. This method proves failure during emergencies.

3. Success depends upon on in-depth knowledge of the pest biology.

4. Unplanned cultivation may have more side effects.