How is the broad-shouldered water strider important?  
  Identify and describe the importance of the broad-shouldered water strider, Microvelia douglasi atrolineata in the rice field.  
An important predator of hopper nymphs

Another common, important, yet smaller predator is the broad-shouldered water strider Microvelia douglasi atrolineata Bergroth, family Veliidae. It primarily attacks hopper nymphs.

In the photo below, see the Microvelia sucking the body fluids from a small brown planthopper nymph.

Microvelia douglasi atrolineata Several predators usually attack larger hoppers at one time.

  Microvelia lives on the surface of paddy water and attacks the insects that fall into the water. This active predator is a very useful natural enemy if the fields are kept flooded.

Results in insectary cages
  Brown planthoppers placed in field cages have a lower rate of survival if the bottoms of their cages are left open to allow the entry of Microvelia. The survival rate is higher if the cages are kept closed.

Natural reduction in brown planthopper Nilaparvata lugens nymph density in field cages caused by predators, especially Microvelia atrolineata, over 18 days in wetland rice.
Brown planthopper density (no./4 hills)
Reduction in density (%)
Few Predators
(2/4 hills)
(closed cage)
Many Predators
(34/4 hills)
(open cage)

Next lesson
  In the next lesson, we will learn about three genera of orthopterans.