Insects of Economic Importance

Animal Husbandry of Class 12

Useful Insects : Most common are the honey bee, silk moth and lac insect.

Honey Bee (Apis)

Apiculture is the rearing and culturing of honey bee for commercial production of honey.

Common Indian species are

Apis dorsata (Rock bee) : the largest, wild type; one hive may yield 15-20 kg honey.

Apis indica (Indian bee) : medium sized bee, used in apiculture; one hive yields 5-6 kg honey.

Apis florea : smallest bee with least yield of honey.

Apis mellifera (European bee) : commonly used for apiculture in Europe.

These are social, colonial and polymorphic insects with 3 castes (Queen, Drones and Workers) showing extreme division of labour and discipline in the hive.

Queen : Generally one per hive, largest in size, as fertile female with only reproductive function, life span is 5-6 years.

Workers

20000 – 80000 in one hive, smallest in size, sterile (diploid) female, performs all functions in hive hence categorised as :

Foragers
Nurses
Scavangers
Soldiers
Retenues
Fanners
Builders, etc.

Drones

The parthenogenetic (haploid) male, middle sized, about 300–400, in number, only to fertilize the queen; driven out from hive, during scarcity.

Structure

The following features relate to workers

Mouth parts - chewing and lapping type; labium is elongated and form honey-spoon, mandible blade-like for manipulating wax, maxilla reduced.

Eye - sensitive to detect even UV-rays

Legs - are modified for collection of nectar or pollen. 1st leg has antennal comb and velum at the end of tibia. 2nd leg has spur to empty the pollen baskets present on 3rd leg’s tibia which also has pecten and auricle.

Whole body is covered with long bristles to which the pollen/nectar get stuck which are broomed by the legs.

Wax glands (5-6 pairs) are present below the sterna of 3rd to 8th abdominal segments

Sting is a modified ovipositor (in workers) connected with the poison gland. If injected in sufficient amount the poison can kill a person. Queen

has sting as 4-5 spines at the end of abdomen (not ovipositor) used only against it’s sister queens.

Reproduction and life cycle

First Swarming (or Nuptial flight or Marriage flight or Honey moon flight):

For producing females the queen requires copulation. It flies out of the hive going high in the sky followed by all drones. The last surviving male fertilizes the queen who then returns to the hive.

Queen lays about 15 lakh eggs in its life time in the batches of 2 to 4 thousands, unfertilized eggs give rise to drones.

Larva (grub) : Without locomotory and sensory organs, stay in their chamber, fed by nurses.

Pupa (chrysalis) : Inactive, non feeding stage within the cell of hive for a short period and then changes into adult.

Development

Queen develops in 9 to 12 days, larva is fed upon royal jelly, the most nutritious diet.

Workers develop in 17 to 19 days, larva is fed upon honey.

Drones develop in 21-24 days, larva is fed upon the pollen or nectar.

At a time 5-6 queens may emerge but the first among them kills her rest sisters.

Queen substance from the queen (a kind of pheromone) prevents other females (workers) from developing into queen.

2^nd Swarming (death swarming)

The new queen always takes charge of the hive while old queen, along with few loyal workers (20,000), leaves the hive and settle at a new

place. Many workers may die during this migration.

Supercedure

Sometimes old queen stays in the same hive but as subordinate of the new queen.

Stinging

Workers go for stinging only when it senses danger to the hive since it dies after. It is a sacrificial behaviour.

Bee dance

It is a means of communication among the hive-mates by which it passes on the coded information about distance, height, direction of food source, or danger signal etc.

These are of different types e.g. tail wagging dance, round dance etc.

Karl von Frisch (1946-69) first deciphered some of these dance codes. He shared Nobel Prize (1974) with Tinbergen who worked on termite behaviour.