Askew & Shaw tested the relationship between attack strategy and host range by comparing the number of host families for idiobiont and koinobiont chalcidoid Hymenoptera associated with arboreal leaf miners in Britain. They found that idiobionts attack about 2.8 times more families of hosts than koinobionts, indicating that in these communities, idiobiosis/koinobiosis is quantitatively related to the degree of host specialization. However, beyond this test, there are no quantitative data that idiobionts generally have broader host ranges than koinobionts. Our purpose here is to test the hypothesis further by comparing the known host associations of two subfamilies of Ichneumonidae which attack forest Lepidoptera: One composed of idiobionts (Pimplinae; excluding the tribe Polysphinctini which are associated with spiders) and the other koinobionts (Metopiinae).