T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Beetle (Chafer) (Grass Grub) Costelytra zealandica

Phylum: Arthropoda 
Subphylum: Uniramia 
Class: Insecta 
Order: Coleoptera 
Family: Scarabaeidae 
Subfamily:Melolonthinae 
Genus: Costelytra
Scientific Name: Costelytra zealandica
Common name: Grass Grub Chafer, Grass grub beetle

The Grass grub beetle (10 mm long) is the natural enemy of the common grass. Native to New Zealand  the Grass Grub, ‘Costelytra zealandica’  has proliferated since we became a pastoral country.
June and July are the most active months of the grass grub. Activity starting in March and building up to June/July then dropping off to finish in September. Where the adult beetle emerges in October and is active till December dependant on area and temperatures. 
The females mate soon after emerging and lay their eggs back near where they emerged from. (unless distracted by night lights). A female lays about 40 eggs in batches, 70 to 200mm below the soil surface. The larvae hatch in about 20 days dependant on soil temperature. They start feeding at these low depths and over the months work their way up to the top 20-30mm of soil in the May to July period. During the dry soil times of summer the grubs hibernate till the soil becomes moist with autumn rains.



  

 

The elytra (wing cases) do not completely cover the abdomen so that a small terminal portion is left exposed.