Predators
       
  What role do orthopterans play in the rice field?  
  Identify and describe the importance of three genera of orthopterans.  
       
A strong preference for eating the egg masses of hoppers and stem borers
  

In the phytophagous group of orthopterans, three genera are standout predators:
  1. Conocephalus, family Tettigoniidae
  2. Anaxipha, family Gryllidae
  3. Metioche, family Gryllidae
These orthopterans have a strong preference for eating the egg masses of stem borers.

Nymphs and adult Conocephalus longipennis (de Haan) eat the egg masses of hoppers and yellow stem borers. One adult can consume three to four egg masses, or two hundred eighty to three hundred twenty eggs per day.
Sword-tailed crickets Metioche vittaticollis (Stal) (left photo) and Anaxipha longipennis (Serville) (right photo) devour the naked egg masses of striped and gold-fringed stem borers.

 
Predators in the rice fields of the tropics
   Several predatory species are capable of killing many hoppers per day. In the field, predators are probably the leading natural cause of nymph mortality. Predators are numerous in the rice fields of the tropics.

Approximate maximum capacity of important predators to kill brown planthopper Nilaparvata lugens prey under artificial conditions.
Predator
Prey killed (no.) daily by one predator
(prey stage)
Egg
Nymph
Adult
Lycosa
-
37.0
29.0
Oxyopes
-
5.6
Cyrtorhinus
8.4
0.2
0.3
Microvelis
-
8.2

 
Partial hand removal of predators
   Partial hand removal of predators in field plots allows green leafhoppers to become abundant. Click here to view data concerning hand removal of green leafhoppers in test plots at IRRI.  
Next lesson
   In the next lesson, we will learn about other animals that destroy insect pests.