Mulberry silkworm –races and their characters – Mulberry plantation studies

Agricultural Study Materials Insects

Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. or Number of generations per year under natural environmental conditions. Based on voltinism, Bombyx mori is divided in to 3 types, namely  

i) Univoltines, ii) Bivoltines  and iii. Multivoltines.

i) UNIVOLTINE RACES: 

  • They produce ONE generation per year. 
  • The larval weight is comparatively higher and cocoons are heavy. 
  • Denier of the silk filament is above 2.3.
  • They are not suitable for summer & winter rearings, since the larvae are weak against unfavourable conditions especially to higher temperature.
  • They lay only diapausing eggs. 

Example: All European races are univoltines e.g., E16. 

ii) BIVOLTINE RACES: 

  • They produce two generations per year. 
  • The length of the larval stage is short. 
  • The leaf consumption to cocoon production (cocoon ration) is less, and the quality of the cocoons inferior to that of Univoltine races. Further, cocoon weight, shell weight, silk % & filament length lesser than uni/mono voltines. 
  • Most of the temperate races are bivoltines and lays both non hibernating and non hibernating eggs 

Example: NB4D2, NB18, KA, NB7 etc.

iii) multivoltine races: 

  • They produce more than 5-6 generations per year. 
  • The length of the larval duration is short. In most of the polyvoltine races the leaf cocoon ratio is high, cocoons are compact grained and cocoon layer is soft. 
  • The length of the filament is short (approximately 400 mts). However, the cocoon filament is fine and clean with little lousiness; but with more lustrous. 
  • The larvae are robust and can tolerate fluctuating environmental conditions and hence best suited for tropical climates. 
  • They lay only non-diapausing eggs. 

Example : Pure Mysore, C. nichi, Hosa Mysore.

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