Uroce r us californ ic us Nott on, f ema 1e. BULLETIN OF THE CALIFORNIA INSECT SURVEY VOLUME 6, NO. 4 THE SIRICID WOOD WASPS OF CALIFORNIA (Hymenoptera: Symphyta) BY WOODROW W. MIDDLEKAUFF (Department of Entomology and Parasitology, University of California, Berkeley) UNIVERSITY OF CALIFORNIA PRESS BERKELEY AND LOS ANGELES 1960 BULLETIN OF THE CALIFORNIA INSECT SURVEY Editors: E. G: Linsley, S. B. Freeborn, P. D. Hurd, R. L. Usinget Volume 6, No. 4, pp. 59-78, plates 4-5, frontis. Submitted by editors October 14, 1958 Issued April 22, 1960 Price, 50 cents UNIVERSITY OF CALIFORNIA PRESS BERKELEY AND LOS ANGELES CALIFORNIA CAMBRIDGE UNIVERSITY PRESS LONDON, ENGLAND PRINTED BY OFFSET IN THE UNITED STATES OF AMERICA THE SIRICID WOOD WASPS OF CALIFORNIA (Hymenoptera: Symphyta) BY WOODROW W. MIDDLEKAUFF INTRODUCTION carpeting. Their powerful mandibles can even cut through lead sheathing. The siricid wood wasps are fairly large, cylin- These insects are widely disseminated by drical insects; usually 20 mm. or more in shipments of infested lumber or timber, and length with the head, thorax, and abdomen of the adults may not emerge until several years equal width. The antennae are long and fili- have elapsed. Movement of this lumber and form, with 14 to 30 segments. The tegulae are timber tends to complicate an understanding minute. Jn the female the last segment of the of the normal distribution pattern of the spe- abdomen bears a hornlike projection called cies. the cornus (fig. 8), whose configuration is The Nearctic species in the family were useful for taxonomic purposes. This distinc- monographed by Bradley (1913). Since that date tive structure alsogives them the common name the description of one new North American of horntails. The ovipositor is exserted and in species in the genus Sirex has been published some species may be quite long, even exceed- (Middlekauff, 1948). The excellent papers by ing the body length. Males are normally smal- Benson (1943, 1951) in which he gives keys to ler than the females, with flattened tibiae and world genera and European species prompted tarsi and with the last abdominal sternite end- me to study more thoroughly the systematics ing in a sharp point. The size of adult siricids and distribution of the siricid fauna of Cali- is quite variable and may vaiy to twice the fornia. size in the same species. The wood-boring The family Siricidae in California is com- larvae are whitish cream or yellow, usually posed of two subfamilies: the Sirioinae con- cylindrical, weakly Sshaped with only ves- taining the genera Sirex, Urocerus, and Xeris, tigial thoracic legs and with a small horny and the Tremicinae containing the single genus spine at the posterior end. Abdominal prolegs Tremen. To date, 13 species and subspecies are absent. in these genera are definitely known from the In California siricids are not as a rule con- state. Sirez nigricornis Fab. is doubtfully re- sidered to be primary enemies of sound timber corded from California (Norton, 1869), and since usually they do not attack healthy stand- subsequent collections have failed to confirm ing trees. They will, however, readily attack it as being present in our fauna. fire-damaged or otherwise injured or dying trees and ones recently felled. Female Sirex areolatus have even been reported as attacking recently sawed redwood lumber. The larval BIOLOGY and adult borings reduce the quality of the Although a considerable amount of study has lumber causing it to be downgraded. Adults recently been done by British and New Zealadd may cause considerable damage while emerg- workers on various biological and life history ing from infested timbers in homes by boring phases of several species of the Siricidae, through plaster walls, hardwood floors, and little is known about our North American spe- GO BULLETIN OF THE CALIFORNIA INSECT SURVEY cies. Most of our biological information con- channel of the ovipositor and not into the ovi- sists of scattered and fragmentary notes on duct. The egg becomes infected as it is laid, ovipositing or on emerged specimens. Except and the wood-destroying fungus penetrates the for the very fine and detailed work by several wood surrounding the larva as it feeds. Experi- British workers on the life history and para- ments have demonstrated that larvae can live sites of the introduced American species Sirex for at least three months on a pure culture of cyaneus Fabricius, not one single American the fungi. It has been theorized that the larvae siricid has been adequately studied. may be more or less mycetophagous and may Adults fly mostly in bright sunshine, and not need cellulose for their subsistance. Parkin females are usually more abundant than males. (1942) found the fungi associated with the lar- Males are reputed to resort to the treetops or vae and confirmed previous work which showed high ground where pairing takes place, and that the adult female becomes infected in the this may in part account for their relative scar- pupal chamber after shedding the pupal skin city in collections. Thar males are not'yet well before emergence. known is probably due to this lack of material A number of natural enemies prey upon the for study rather than through any intrinsic dif- horntails; of these, various Hymenoptera are ficulties in distinguishing them. The genitalia most important. Members of the cynipid genus seem of slight and doubtful significance for Ibalia (fig. 18) and the ichneumonid genera purposes of taxonomic distinction. Rhyssa and Megurhyssa (fig. 19) parasitize Females usually oviposit in trees weakened the larvae of Siricidae. or dying as a result of fire, disease, or other The life cycle of Zbalia requires at least injury. Occasionally they select a tree which two years. It oviposits in the young siricid to all appearance is still healthy. Ovipositing larva just before or more rarely just after it females insert their ovipositors deeply into the hatches, utilizing the oviposition bores of the wood and lay their eggs. Sometimes they are Sirex for this purpose. The parasite larva is unable to withdraw their ovipositors and die in endoparasitic. Parasitized host larvae confine this position. their borings largely to the outer parts of the The larvae bore into the trunk of the tree, tree trunk and usually make their final cell making perfectly cylindrical holes in the wood just under and approximately parallel to the and pack the frass from their borings in the surface. tunnels behind them. Tremex may complete Females of Rhyssa and Megurhyssa lay their larval growth and pupate within a year, but no eggs in the burrow of, and near to, the almost definite data are available. According to Hanson fully grown host larva or the pupa by piercing (1939), the life cycle of Sirex cyaneus normally the solid wood with their ovipositors. Feeding extends for a period of three years from egg to by the ichneumonid parasite is entirely ecto- adult, but development may ,be retarded and the parasitic and takes only a few weeks, during adult insects may not emerge from the timber which the host larva may burrow a little farther. until several additional years have elapsed. A The winter is passed by Rhyssa or Megarhyssa number of generations may be present in a as a resting larva. Pupation takes place in the single log at any one time, and this greatly spring, and the whole life cycle normally oc- complicates understanding the composition of cupies one year. the population. Woodpeckers, contrary to popular belief, Horntails are of additional interest to biol- consume few if any siricid larvae. Beal(19111, ogists because of the symbiotic relationship in his paper on the food of North American of Sirex, Urocerus, and Tremex with certain woodpeckers, fails to mention larvae in their wood-destroying fungi. The fungi are commonly diet. found apart from the siricids but with the ex- -As in previous publications in this series, ceptions of Xeris (Francke-Grosmann, 1939) all the locations of the specimens from which the female wood wasps examined have had asso- records have been taken are reported. The fol- ciated fungi. No fungi or fungal sacs have lowing abbreviations have been used for insti- been found in adult males. tutional and other collections: In the female, the fungus is contained in a California Insect Survey, University of Cal- pair of small invaginated intersegmental fungal ifornia, Berkeley (C.I.S.) sacs which project into the body cavity at the California Academy of Sciences (C.A.S.) basal end of the ovipositor, opening into the University of California, College of Agri- THE SIRICID WOOD WASPS OF CALIFORNIA 61 culture, Davis (U.C.D.) (fig. 5); eye distinctly longer than broad University of Oregon (U.O.) (fig. 17); hind tibia with two apical spurs. California State Department of Agriculture, ........... Urocerus (p. 66) Sacramento (C. S. D. A. ) California Forest and Range Experiment Station, Berkeley (C. F. R.E.S.)' Genus Sirex Linnaeus, 1761 Los Angeles County Museum (L.A.C.M.) San Jose State College (S. J.S.C.) Sirex is Holarctic in distribution with about University of Idaho (U.I.) 20 species described, 9 of which occur in I am indebted to the authoritjes of these North America; all but 3 of these are reported institutions, as well as to individuals whose from California. The females oviposit in the records are separately rsported, fo: the privi- trunks of various species of conifers in the lege of studying the specimens which have genera Sequoia, Cupressus, Libocedrus, formed the basis of this paper, and to Mrs. Pseudotsuga, Pinus, and Abies, and the larvae Celeste Green, Scientific Illustrator, for the are wood borers. Species in the genus Sirex drawings which accompany this study.