SAWFLY LARVAL HOST SUMMARY

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

TAXON NAME Family      Subfamily	# sp. with at least 1 larval host record	# sp. without larval host record	% with larval host(s) record
Argidae	21	2	91
Cephidae	6	1	86
Cimbicidae	6	2	75
Diprionidae	19	0	100
Orussidae	2	2	50
Pamphiliidae	32	14	70
Pergidae	3	0	100
Siricidae	9	0	100
Tenthredinidae
Allantinae	35	11	76
Blennocampinae	27	8	77
Heterarthrinae	22	1	99
Nematinae	76	12	86
Selandriinae	22	33	60
Tenthredininae	15	83	14
Xiphydriidae	9	1	89
Xyelidae	9	0	100
Total	313	170	65

Table 3 summarizes the degree of knowledge on larval hosts for species in the Mixedwood Plains Ecozone. The biology of eastern North American sawflies has been much studied over the past 100 years because several species are of great economic importance in forest management and in agriculture as pests of woody fruit plants and cereals. 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; 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 damage. 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 damage especially in 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 the three species of Acordulecera cause only minor damage to oak trees.

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

Larvae of the Tenthredinidae feed on a wide range of host plants. The following observations are at subfamily level. Larvae of the Allantinae feed mainly on woody plants. Few species 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 several tree species of economic importance. Larvae of Nematinae are generally known to attack willows and poplars, but in our region the feeding habits show a much wider range of hosts. Most hosts are woody plants but a few feed on herbaceous plants. Though most larvae are external feeders, some develop in galls on twigs, petioles and leaf blades. Some of the species cause 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 some species of the genus Dolerus are beneficial since they feed on horsetails, poisonous plants quite common in pastures. Larvae of the Tenthredininae feed on a extremely wide range of herbaceous plants. The hosts of most species is 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 numerous species pollinate a wide range of flowers. This subfamily consist mainly of beneficial species.

Larvae of Xiphydriidae are wood borers of deciduous trees mainly. The damage is not of 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 are not economically significant, and those of other genera are too uncommon to be of significance.

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