Henri Goulet. 1998. Sawflies (Hymenoptera: Symphyta) in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

SAWFLIES
(HYMENOPTERA: SYMPHYTA)

Henri Goulet

SAWFLY LARVAL HOST SUMMARY

Table 3. Number of species (recorded and expected) with at least one recorded larval host and those without any larval host record. The results are given for each family, subfamily of the Symphyta.

* Member of this familly are parasitoids on woodboring beetles. The above table is only about host plants consumed by Symphyta.

Table 3 summarizes the degree of knowledge on larval hosts for species in the basin. Because of the economic significance of several species of sawflies in agriculture and forestry, efforts were invested into their biology over the past 100 years. It is unusual that host plants of a major group of insects are known for about two thirds of its species. Most species attack wild plants of no economic significance, many attack economic plants without significant damage, and a few are significant pests of economically important plants. In the agricultural and ornamental context, most pest species of sawflies are accidentally introduced into North America. In the forest context, the pest species are a mixture of introduced and native sawflies. In the following review by families and subfamilies, I try to extract the most salient facts of economic significance.

Larvae of Argidae mainly affect tree crops. The larvae of one species feed on pears, and those of one species is beneficial as they feed on Portulaca, an extremely common weed.

Larvae of Cephidae affect many agricultural crops, but those feeding on wheat, oats and rye cause very significant damages. They are also significant in the currant and bramble fruit production.

Larvae of Cimbicidae feed on a wide range of deciduous trees and honeysuckle bushes. Their impact is not greatly significant.

Larvae of Diprionidae feed strictly on conifers and cause important damages especially to young conifer plantations.

Larvae of Orussidae are beneficial external parasites on beetle larvae mining tree trunks.

Though most species of Pamphiliidae cause minor damage to trees or woody bushes, a few are economically important on pines and cherries.

Larvae of Siricidae develop usually in recently dead branches or trunks of trees. They cause significant damages for the wood industry, though their activity is primarily linked to recycling which leads to soil formation.

Larvae of the Tenthredinidae feed over a wide range of host plants. The following observations are at subfamily level.

Larvae of the Allantinae are mainly feeding on woody plants. Very few species are known to cause significant damage to forest or agricultural crops.

Larvae of Blennocampinae feed on a wide range of sedges, trees, bushes and herbs. None seems to be very significant economically.

Larvae of the Heterarthrinae either feed on leaves of trees and shrubs or are leaf miners of several tree species. The external leaf feeders are important defoliators of cherries while leaf miners significantly affect photosynthesis of some economically important trees.

Larvae of Nematinae are generally attack willows and poplars. Most hosts are woody plants with few herbaceous plants. Though most larvae are external feeders, some develop in galls on twigs, petioles and leaf blades. Some of the species cause very significant damage to agricultural, forest and ornamental plants.

Larvae of Selandriinae mainly feed on ferns, sedges and grasses (one species is a minor pest of wheat). Larvae of three major lineages of the genus Dolerus are beneficial as larvae feed on horsetails. Horsetails are poisonous plants found quite commonly in pastures.

Larvae of the Tenthredininae feed on an extremely wide range of herbaceous plants. The hosts of most species are not known, but in Europe the host range extends from ferns to Asteraceae. In North America, there are hardly any plants of economic importance consumed by members of this subfamily. A most unusual aspect of feeding behaviour is seen in adults. In most species, adults are predatory. Moreover, adults of many species especially in the ecozone pollinate a wide variety of flowers. This subfamily consists mainly of beneficial species.

Larvae of Xiphydriidae are wood borers of deciduous trees mainly. The damage is of no economic significance since they attack small dead branches. However, their role is like that of the Siricidae as they are involved in soil formation.

The larvae of Xyelidae feed either on male flowers of pines or on leaves of deciduous trees. The pine feeders seem to be of no economic significance, and those of other genera are too uncommon to be of significance.