Methods of insect collection, preservation, display and storage by Dr. T. Krishna Chaitanya

This topic will deals with the Methods of insect collection, preservation, display and storage of Insects.

1. 1 Dr . T. KRISHNA CHAITANYA Assistant Professor (Agricultural Entomology) School of Agricultural Science & Technology, NMIMS, Shirpur Methods of insect collection, preservation, display and storage

2. Aim : To learn the ways and means of collecting, killing, preserving, pinning, labelling and display of insects and their storage methods. Also to know the method of preparing insect killing bottle/ poison bottle, relaxing container and Riker mount . NEED FOR INSECT COLLECTION To learn about insect biology, habit, habitats and behaviour, To study seasonal incidence of insect pests in fields, To determine insect population and justify insect management measures, To identify the natural enemies, present in the ecosystem. As a hobby. 2

3. Insect net : 1. Aerial net (Butterfly net): 3

4. An aerial net is used to collect aerial insects during flight (active fliers like butterflies, moths, dragonflies, flies, wasps, etc.). It is light in weight and has three parts viz ., metal ring hoop (30-45 cm dia.), long wooden / aluminium handle (90 – 120 cm long; 2.5 cm dia.) and porous cloth/ mosquito net cloth bag. The diameter of hoop and the depth of bag should be in the proportion of 1:2. This net can be made easily by using an old badminton racquet, after removing guts and fixing a cloth bag. 4

5. 5 Sweep net :

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11. It is heavier than aerial net. It is used to collect leafhoppers, grasshoppers, small insects, etc. It has a large hoop (38 cm dia.), a short stout handle (75 cm long) and a muslin cloth bag / tough cotton cloth bag. Muslin cloth bag can be used for non-bushy plants like graminaceous or vegetable crops; whereas tough cotton cloth bag can be used for collecting insects from bushy/ spiny plants like cotton. 11

12. Aquatic/ Dip net : 12

13. It is used to collect aquatic insects/ aquatic stage of aerial insects from still / running water. It is similar to aerial net, except the length of the bag. The diameter of the hoop/ring is equal to the length of the bag. Aquatic nets also have heavy duty net bags and handles and have square to triangular thick wire hoops. 13

14. Aspirator : Aspirator can also be called as “ Pooter ” (named for inventor, William Poos). It is used to collect small and minute insects without any damage. There is tube type, vial type and simple type aspirator. 14

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17. 3. Berlese funnel : To collect soil inhabiting insects, like mites, collembolans, etc., from debris, organic matter, litters and soil. 17

18. How to use Berlese funnel? Soil or debris is placed on a wire-mesh of funnel, over which an electric bulb is kept. As the debris dries under the heat of the bulb, the negatively-phototrophic insects or the humid environment-preferring insects start dropping down the funnel into collecting vessel with alcohol kept below. 18

19. 4 . Baiting : Insects attracting baits viz ., sugar, rotting fruit, meat, animal dung, newly felled logs, etc. are used to collect domestic insects (cockroach, flies, ants, beetles, termites). 19

20. 5. Traps : Different types of traps are used for collecting various groups of insects. Light trap (phototropic insects), pheromone trap (moths -species specific), sticky trap ( thrips , whiteflies), suction trap (whiteflies), methyl eugenol trap (fruit fly), water pan trap (brown planthopper ), pitfall traps (ants, antlion grubs and other soil insects). 20

21. Light trap (phototropic insects) 21

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23. Pheromone trap (moths -species specific ) 23

24. Sticky trap ( thrips , whiteflies) 24

25. Suction trap (whiteflies) 25

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27. Methyl eugenol trap (fruit fly) 27

28. Water pan trap (brown planthopper ) 28

29. Pitfall traps (ants, antlion grubs and other soil insects) 29

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34. 6. Hand picking : Large and less active insects can be collected. Tedious method; stinging/ biting insects can not be collected. eg . Beetles, grasshoppers, etc. 34

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37. II. KILLING INSECTS Killing should be done immediately after capture, especially dragonfly, damselfly, butterfly and moths. Potassium cyanide, ethyl acetate, carbon tetra chloride ( Carbona ) and chloroform are commonly used for killing insects. Potassium cyanide kills the insect quickly, cyanide charge will last for long time but it is highly poisonous, cause discoloration of the coloured specimen. Ethyl acetate kills the insects more slowly but allows the insect to be kept in it longer without becoming brittle. 37

38. Preparation of killing bottle Ethyl acetate killing bottle : Take a 300 ml wide-mouthed bottle with a closely fitting screw cap. Pour one-inch layer of plaster of Paris slurry, immediately after mixing. Allow it to dry for at least 48 hours. When dry, saturate the plaster of Paris with ethyl acetate . Cover it with a thick cardboard/ filter paper disc and add a few strips of blotting-paper/ newspaper inside the bottle, to keep it dry and avoid condensation of water droplets on the sides of the bottle . Frequent priming with ethyl acetate is necessary , for the killing bottles to retain their potency . 38

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40. Precautions While handling poison bottle : Label the poison bottle as „ POISON’ (in English and in vernacular language) and the danger sign (human skull & cross bones ). Bind the bottom of the bottle with cellotape to protect it from breakage. Always keep it tightly closed and keep out of reach of children . While handling insects : Don‟t mix small insects with scaly insects. Don‟t mix delicate insects with large insects . Use a separate large killing bottle for moths and butterflies and another for beetles and grasshoppers . Never overload the bottle, remove the insects as and when they are killed. 40

41. III. PRESERVATION OF INSECTS Materials required for preservation : Paper envelops or triangles or folds : Large winged insects such as dragonfiles , butterflies or moths can be temporarily preserved after collection (to preserve wing colouration ). Cut the absorbent paper/ newspaper into rectangles with their sides in the proportion of 3:5. Bring the diagonally opposite corners together to leave two projecting flaps. Write the data regarding collection on outer side of a projecting flap . Keep the immobilised insect in between overlapping triangles. Fold the flaps to produce a triangular envelope. 41

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43. Relaxing container : Stiffness in the dead insect can be removed by placing it in a relaxing container. Relaxing jar is made of rustless metal, tin or glass, with a tightly fitting lid or screw cap. It contains a layer of sand (5 cm)/ any absorbent material (synthetic sponge), which is saturated with water and a few drops of formalin or carbolic acid (phenol ). Over the wet sand, several layers of paper discs are placed. Keep the dried specimens in a small open box (to avoid direct contact with moist sand). Close the lid tightly and allow remaining for a day or two until they become flexible. 43

44. Entomological pins : They are slender, hard with a pointed tip and a small head; made of non-corrosive metal (pure nickel). There are three types of entomological pins viz ., English, Continental and Minuten (or points). No.16 and 20 pins used for pinning larger and smaller insects, respectively and minutens for very small insects . Minutens are very thin, slender, delicate and headless pins . Common bell pins are undesirable as they are too thick and short; and usually rust or most commonly a green substance called verdigris forms where the pin comes into contact with insect body. 44

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46. Setting board : It is useful for spreading the wings of large insects. It consists of a wooden block with a groove. Both block and grooves are lined with thin sheets of cork. A thermocole sheet with a centrally cut groove can also be used. 46

47. METHODS OF PRESERVATION DRY PRESERVATION It is the best and most common method to preserve hard bodied insects; internal organs are dried; only exoskeleton is retained. 47 Name of the insect Place of insertion of pin Most insects Thorax Dragonflies and damselflies Center of the thorax Earwig Right tegmen

48. 48 Grasshopper, crickets, preying Right of mid-line pronotum mantis, and cockroach   Right of mid-line pronotum Stick insect Metanotum Bugs Right side of scutellum Beetles Right elytron, midway on the overall body Flies, wasps and bees Mesothorax , slightly to right of the mid –line Butterfly and moth Centre of the prothorax.

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55. Double mounting : When insects are too small, double mounting is done. The specimen is first attached to a piece of card or pith or cork by staging, carding or pointing/ gumming and then fixed to the insect box using a large pin. 55

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57. 2. LIQUID PRESERVATION 57 Soft bodied insects like silverfish, springtails, mayflies, aphids, thrips , immature stages viz ., caterpillar, grubs, etc. Can be directly preserved in liquids like 70% ethyl alcohol or methylated spirit and formalin (4 %). Before preserving them in liquid preservative, their colour and tissues should be fixed by keeping them in boiling water. Smaller specimens can be dipped in boiling water for 30 seconds; while specimens of immature stages should be dipped in boiling water for extended period . All these preservatives are highly volatile; hence preserve it in screw cap vials and seal the stopper with paraffin wax, which reduces evaporation of preservatives. Label is written with pencil and placed inside the vial. Careful examination of liquid preserved specimens is done once in a year and the liquid is replaced.

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60. 3. SETTING/ STRETCHING/ SPREADING : Setting is essential for full display of their features and to study the wing characters. It is the method by which wings, antennae and legs are spread . Wings of moths, butterflies, dragonflies and damselflies are set on either side . In grasshoppers, wings on one side alone are set . Setting boards are used for setting, before the insects become stiff. 60

61. How to set a butterfly ? Pins are inserted through the thorax properly and placed on the groove. Wing base is in level with the top surface of the setting board . Position the legs with pins. Hind margin of the forewing is maintained at right angles to the body . Push the front edge of the hindwing under the hind margin of the forewing. Use separate large card board strips for pressing the wings either side . Support the abdomen with pins crossed beneath it to form a platform to prevent abdomen from sagging while drying . Orient the antenna symmetrically . Insect is allowed for 'setting' in this position for hours or days together. Keep the specimen on the setting board until the abdomen becomes stiff. Protect the insects from ants, lizards, etc. 61

62. BLOWING OF LARVA Blowing is the popular method of preserving soft bodied larva. This method consists of removing the internal contents of the larva and then inflating it like a balloon to its natural size and drying it in this position in a blowing apparatus. For blowing small sized larva a disposable syringe with a hypodermic needle can be used. 62

63. Method of blowing insect larvae Drown the caterpillar in warm water Place the caterpillar over a filter paper Make a slit at the anal end using a sharp blade Keep the larva on a blotting paper spread over the table. Roll down a glass rod or a pencil on the insect, from the head to anal end. All the internal contents will be expelled by this act. Pull out the alimentary canal protruding out through the anus by using forceps and cut it off with a razor blade Insert the syringe needle or nozzle of the blower into the anal slit and fasten in position with a thread without puncturing the body Inflate the exoskeleton by pressing the plunger of the syringe or the bulb of the blower until it reaches the normal size Keep the inflated caterpillar inside a hot chamber for a few minutes, until the integument dries and turns stiff. Gently rotate larva so that all sides get uniformly heated and turn stiff. Never expose the larva to direct flame, don’t burn it , Gently remove the syringe needle or nozzle Stick the blown up caterpillar to a match stick with gum Place it in the transparent box through match stick Display the life stages in the transparent glass/ plastic box 63

64. IV. LABELLING Label should be of a uniform size (12 x 6 mm) cut out from a stiff paper or reference card. One label should contain the details on Name of the locality, date of collection and name of collector, insect, host and habitat. Second label shall contain systematic details of insects. It should be neatly hand written by Indian ink. Label run half way up the pin projecting in same direction as specimen. 64

65. V. DISPLAY AND STORAGE 1. STORAGE BOX : 65

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68. Use of preservatives Naphthalene balls mounted on pins are pinned inside to repel museum insects. This is done by heating the head of the pin in flame and pressing it against a naphthalene ball. The ball melts at the point of contact. The pin head enters the ball and the melted naphthalene solidifies around the pin head . Naphthalene flakes can also be kept in perforated envelopes and pinned in the boxes . Para dichloro benzene (PDB) crystals can be used, which will not only keep off museum insects but also check infestation . CCN mixture (Creosote: Chloroform: Naphthalene mixture at 2:1:1 ratio) is a disinfectant and preservative liquid and effective to protect insect specimens in box . Ant wells can be used to prevent ants. 68

69. 2. RIKER MOUNTS A Riker mount is a flat container having a glass (or transparent) cover, containing cotton wool, and used for mounting a plant or insect specimen. A Riker mount is so named after an American botanist, Riker. In Riker mounting, the entire life cycle of the insect is to be displayed under dry condition. The adult and pupa are preserved after poisoning. The larval specimens are processed by removing the body contents and blowing. It can be used as an excellent teaching aid. 69

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