Life Cycle, Food and Environment of Bombyx Mori

LIFE CYCLE, FOOD AND ENVIRONMENT REQUIREMENT OF BOMBYX MORI Submitted To:

Submitted By:

Mr. Minraj Pokhrel

Babu Ram Panthi

Asst. Professor

B.Sc.Ag. 8 Sem

Department of Entomology

Roll.No: 58

IAAS, Rampur Campus

IAAS, Rampur Campus

th

January 2012

Abstract

The silkworm, Bombyx mori, is used for sericulture and is one of the most economically important insects in the world. The species of silkworm usually raised by sericulturists is B. mori (Lepidoptera: Bombycidae). Silkworms undergo complete metamorphosis. Larvae feed on the leaves of the mulberry (family Moraceae, genus Morus); they will consume other genera in this family, but growth rate is reduced. At 23 to 25°C the five instars require 25 to 30 days to hatch. Toward the end of fifth instar, B. mori spin a cocoon over a 3-day period and pupate within that cocoon; the pupal stage lasts for about 10 days. After molting to the adult has occurred inside the cocoon, the moth emerges. The quality and quantity of mulberry leaves play an important role in growth and development of silkworm (Bombyx mori L), particularly during adult larval stage, which in turn influence the expression of cocoon productivity traits. This also leads to the increase in body size and dry weight of cellular mass which are dependent on the rate of metabolism, absorption of nutrients, and stage of development. The larval growth, cocoon quality and nutritional indices are significantly higher when larvae are reared under optimum temperature and humidity with adequate feed quantum as per the recommendation. Maintain optimum range of temperature and humidity by artificial heating (electric heater etc.) or cooling (wet sand bed may be formed in the floor during dry season). Keywords: Bombyx mori, Morus alba, Larvae, Life Cycle, Food, Environment

Table of Contents

1. Background………………………………………………………………………………………………………………. 1

2. Objectives…………………………………………………………………………………………………………………. 1

3. Introduction…………………… Introduction………………………………………………………………… ………………………………………………………………………………. …………………………………. ………. 2

•

Life Cycle…………………………………………… Cycle……………………………………………………………………………………………… …………………………………………………………. ………. 2

•

Food Requirement………………………… Requirement……………………………………………………………………… ……………………………………………………………… ………………… 4

•

Environment Requirement……………………… Requirement……………………………………………………………………… ……………………………………………………. ……. 4

4. Methodology…………………………………………………………………………………………………………….. 5

5.

Summary and Conclusion…………………………… Conclusion…………………………………………………………………………… …………………………………………………………….. …………….. 5

References

Life Cycle, Food and Environment Requirement Requirement of Bombyx mori January 1, 2012

Background

Figure 1: Adult of Bombyx mori

Figure 2: Different life stages of Bombyx mori

The silk worm (Bombyx mori L.) is domesticated insect, which feeds exclusively on mulberry leaves to produce raw silk in the form of cocoon. It is an economically important insect, being a primary producer of silk. . It is entirely dependent on humans for its reproduction and does not occur naturally in the wild. Sericulture, the practice of breeding silkworms for the production of raw silk, has been underway for at least 5,000 years in China, from where it spread to Korea and Japan, and later to India and the West. The silkworm has been extensively utilized as model organism in biological studies as well as for economic gains. The life cycle of silk worm is greatly influenced by environmental stress and nutrition particularly during larval period. Environmental factors such as temperature, humidity, light, air, feed quality as well as quantity have intimate influence on its growth and development. The consumption and utilization of food in insects facilitate the understanding of the adaptability of insects to the environment. Humidity also plays a vital role and directly influences the physiological functions of the silkworm. With the increase of temperature (20° – 30°) leaf to silk conversion rate decreases. . Day to day change in weather during the larval rearing poses great threat to the cocoon crop. The larval growth of silkworm is under direct influence of temperature and humidity. Silk worm larvae spun best quality cocoons at 22°C and 65% RH (Ramachandra et al., 2001; Srivastava et al., 2007; Suresh Kumar e t al., 2008). RH levels, above and below the optimum, result in poor performance of the silkworm larvae (Furdui et al., 2010).

Objectives: To know about the life cycle of Bombyx mori. To know about the food requirement of Bombyx mori. To know about the environment requirement of Bombyx mori. 1

Reviewed By: Babu Ram Panthi, B.Sc.Ag. 8 th Sem


Introduction: Life Cycle

Life cycle of silk worms has four stages: such as egg, Larva, Pupa and moth. Domesticated Mulberry silk worms are univoltine, bivoltine and multivoltine. Univoltine silkworm completes one generation, Bivoltine complete two generation and multivoltine silk worm completes 5-6 generations

per

year.

The

univoltines

lay

diapausing eggs and only hatch once in a year at spring season. Bivoltines lay both type of eggsdiapausing eggs and non diapausing eggs which hatch in spring season and autumn season. Multivoltine don’t lay diapausing eggs.

Eggs: The size, weight, shapes and color of the eggs varies with the silkworm races, season and

nutrition of mother moths at larval stages. Generally the eggs are ovoid, spherical or ellipsoid in shape and flat on one side. The female moth lays

Figure 3: Life cycle of Bombyx mori

400-500 eggs on mulberry leaves or artificially prepared butter cups. 100 eggs weigh about 60 mg. the silkworm eggs hibernated during winter will hatch in spring when the mulberry sprouts. Generally the eggs hatch in 9-11 days at proper temperature and humidity condition. Larvae: The larvae are polypodous or eruciform type. The head is hypognathous, heavily

chitinized and bright brown in color. There is spinneret, as the median process, at the distal portion of the labial prementum through which silk glands open and silk exudes. It has three pairs of ocelli or simple eyes. The thorax bears 3 pairs of cornical short, jointed true kegs and th

the prothorax has a pair of spiracles laterally. Abdomen has nine visible segments as the 9 , th

10

and 11

th

segments are fused to form the apparent ninth segment that bears the paired rd

th

th

prolegs one in each. The 3 , 4 , 5 each. The dorsum of the 8

th

th

and 6

abdominal segment bears paired prolegs one in

segment has a projection called caudal horn. The first eight

abdominal segments have a pair of spiracles laterally. The larvae go through four moults and have five instars. The newly hatched worms are black in color and covered with bristles and thus resemble tiny black ants at a glance so called ant worms. The worms are about 3mm long, have 13 segments. 2



The worms become smoother and lighter during different succeeding instars. Among five larval instars the first three are known as young worms and the rest two instars are called grown up worms. The larvae raise their head and search a shelter for resting and secrete silken thread and cover themselves with cocoon. Pupae: Pupae are soft and white soon after the moult that occurs within the cocoon spun by

the final instar larva. It takes 48-72 hours to spin its cocoon and transforms into pupae in 2-3 days and after another 10 days emerges as moths. The pupa is a non-motile and non-feeding stage. The color of the pupal cuticle, compound eyes, and wing pads change with the age of the cocoon and is useful for the gross examination of the age of the pupae. Adults: From the cocoon the moth emerges and emergence takes place in the morning.

Copulation also takes place just after emergence. The moths have prominent bipectinate antennae and compound eyes on the head. The coiled proboscis is non functional. There are three pairs of thoracic legs and two pairs of wings in the thorax region. Moths cannot fly but males are more active than females in movement. Table 1: Life cycle (in days) of different races of Bombyx mori Stages

Univoltine

Bivoltine

Multivoltine

Embryonic period Larvae Pupae Adult

11-14 24-26 12-15 6-12

11-14 24-26 12-15 6-10

9-12 20-24 10-12 3-4

Table 2: The summary of life stages of mulberry silkworm races Stages

Sub stages

Duration (days)

Eggs

Multivoltine or non diapausing Diapausing I Instar II Instar III Instar IV Instar V Instar Cocooning/Mounting Pupation Emergence Life

11-12 Over wintering 3-4 2-3 3-4 3-6 7-8 2-3 2-3 3-4 3-4

Larvae

Pupae

Adults

3


Life Cycle, Food and Environment Requirement Requirement of Bombyx mori January 1, 2012 Food Requirement

A silkworm's (Bombyx mori ) preferred food is mulberry (Morus alba) leaves, but it may also eat the leaves of any other mulberry tree (i.e., Morus rubra or Morus nigra) as well as the Osage orange. The quality and quantity of mulberry leaves play an important role in growth and development of silkworm (Bombyx mori L), particularly during adult larval stage, which in turn influence the expression of cocoon productivity traits. This also leads to the increase in body size and dry weight of cellular mass which are dependent on the rate of metabolism, absorption of nutrients, and stage of development. The larvae of silkworm is the most important stage in the context of food requirement as mulberry leaves consumption takes place during the larval stage of silkworm. So, considerations should be made in fulfilling the required amount of food (mulberry leaves) at proper stage of time. Use fresh, tender dark green and succulent leaves raised as per recommended package old practices. Use nutritious leaf with lesser moisture content and medium to coarse type. In the initial stage use the 2nd and 3rd full blown leaves below the glossy leaf and gradually as the worms grows, use medium leaf for feeding the worms. Pluck mulberry leaf during the cooler hours of the day and carry it i t in wet gummy bags or baskets to the rearing house. Store the leaf in wet leaf chambers of earthen pot kept in cool and dark place. During summer, sprinkle water on the leaf and cover with wet gunny cloth. Use the leaf plucked in the morning for afternoon and night feeding. Use the leaf plucked in the afternoon for morning feeding of the next day. Collect 55 to 60 days old fully grown leaf. Do not feed the worms with withered leaf as it leads to the reduction in consumption and growth of worms. During high humid condition increase the number of feeds/day, each feed with lesser quantity of leaf and supply the worms with chopped leaf (1 leaf cut into 4 pieces)

Environment Requirement

The bivoltine silkworm larvae should be reared under optimum temperature and humidity conditions and fed with recommended quantity and quality mulberry leaf with sufficient leaf moisture. The larval growth, cocoon quality and nutritional indices are significantly higher when larvae are reared under optimum temperature and humidity with adequate feed quantum as per the recommendation. However, most of the feed conversion efficiency is higher when worms are reared under high temperature and 30% quantity of feed (Rahmathulla et al. 2004).

4



Maintain optimum temperature and humidity; regulate the spacing and feeding dose for the healthy growth of the silk worms as recommended in the table 3. Maintain optimum range of temperature and humidity by artificial heating (electric heater etc.) or cooling (wet sand bed may be formed in the floor during dry season).

Table 3: Environmental condition, spacing and feeding st

nd

Factors

1 Instar

2

Instar

Temperature(°C) Humidity (%) Feeds per day (No) Quantity of leaf (kg) Quality of leaf Leaf size (sq. cm) Spacing (sq. m)

27-28 85-90 4 2.5-3.0 Tender 0.5-1.5 0.36-1.35

27-28 85-90 4 13-14 Tender 1.5-4 1.35-4

rd

th

th

3 Instar

4 Instar

5 Instar

26 75-80 4 50-40 Medium 4-6 4-9

25 70-75 4 150-120 Medium Entire leaf 9-20

24 65-70 4 1000-800 Coarse Entire leaf 20-20

Methodology: To prepare this report, I consulted textbooks, reference books and lecture notes. Many findings from research also helped me much which was published in many journals. Review is made by consulting as many books and journals and through net surfing.

Summary and Conclusion For the best quality of silk production, silkworm should be reared under optimum temperature and humidity and fed with recommended quantity and quality mulberry leaf with sufficient leaf moisture. The larval stage is the most important stage for the better cocoon production. For the efficient and quality production of silk, lifecycle of silkworm should be understood. One should know the proper time for mounting of the larvae and cocoon maturing for silk extraction. Temperature and humidity factors plays important role for the food consumption and utilization. Humidity also plays a vital role and directly influences the physiological functions of the silkworm. With the increase of temperature (20° – 30°) leaf to silk conversion rate decreases. The mulberry leaves used for the larval feeding should be fresh, tender, dark green and succulent with lesser moisture content.

5


References

V.K. Rahmathulla, V.B. Mathur and R.G. Geetha Devi. June 2004, Growth and Dietary Efficiency of Mulberry Silkworm (Bombyx mori L.) Under Various Nutritional and Environmental Stress Conditions, Philippine Journal of Science 133 (1): 39-43 Ramachandra, Y.L., G. Bali and S.P. Rai, 2001. Effect of temperature and relative humidity on spinning behavior of silkworm (Bombyx mori L). Indian J. Exp. Biol., 39: 87–89 Srivastava, P.P., P.K. Kar, A.K. Awasthi and S.R. Urs, 2007. Identification and association of ISSR markers for thermal stress in polyvoltine silkworm Bombyx mori. Russian J. Genet., 43: 858–864 Suresh Kumar, N., H.K. Basavaraja, P.G. Joge, G.V. Kalpana and N.M. Reddy, 2008. Heterosis Studies on Hybrids of Cocoon Colour Sex-Limited Breed of the Silkworm, Bombyx mori L. under different environments of temperature. J. Ent. Res. Soc., 10: 1–12 Furdui, E.M., L.A. Mărghitaş, D. Dezmirean, C.M. Mihai, O. Bobiş and I. Paşca, 2010.

Comparative Study of Biological Characteristics of Larvae, Crude and Dried Cocoon in 7 Races of Silkworm Bombyx mori L., L., Raised in Transylvania Transylvania Area. Area. Biotechnology., 43: 490–493

Anim. Sci.

Life Cycle, Food and Environment of Bombyx Mori

Recommend Documents