The damage caused by the larvae of four Melolonthine and one Ruteline scarab species to four grasses and Trifolium repens grown in pots was examined for interactions between species with and without manure added to the soil. Only slight interactions between scarab species and plant species were detected in the damage to pastures, and these were caused by a differential insect response to Trifolium. Most scarabs damaged Trifolium as much as they damaged the grasses, but Anoplognathus sp. appeared to avoid Trifolium in the absence of manure. Sericesthis geminata Boisd. caused more damage to Trifolium than S. vigilans (Sharp) or Rhopaca magnicornis Blkb.

The addition of manure to soil reduced to negligible proportions the damage to all pasture species except Phalaris tuberos, which suffered significantly greater reduction of foliage than other plants in the presence of manure. The highly significant alleviation of damage by manure occured with all scarab species except S. vigilans, which did not cause damage even in the absence of manure.

In this short-term experiment survival and pupation were not influenced significantly by plant species or manure.