Genus: Tremex Jurine 1807
Common names: horntails, woodwasps, tremex wasp
The genus Tremex in the family Siricidae occurs in North America and Eurasia. This is a small genus with 33 species. Tremex columba (Fabricius) is the only species native to North America. However, Tremex fuscicornis (Fabricius), native to Eurasia, was unintentionally introduced to Canada, Australia, and Chile. Tremex larvae are wood-boring in hardwoods (Baldini 2002).
Tremex is found throughout the Holarctic region. There are 33 known species; only two occur in North America, one native species, T. columba, and the introduced species T. fuscicornis (Taeger and Blank 2011).
Distribution map of Tremex sp. by GBIF: https://www.gbif.org/species/1358460
Variations in abdominal coloration led to Tremex columba being divided into multiple species. However, using both DNA and morphology, Schiff et al. (2012) found that the three-color forms were all the same species. The reddish-brown form is found from southern New York and Illinois into the southeast. The darkest form with black and yellow marking is widespread in eastern North America from Saskatchewan to the Atlantic coast and south to Georgia. A form with a pale reddish-brown abdomen, black transverse bands, and yellow-tinted wings, occurs in the middle of North America from Canada, east of the Rocky Mountains across the Great Plains and south into northern Mexico. Wing color also varies geographically, with dark-winged forms to the south and amber-colored wings to the north.
Female Tremex oviposit in dead or weakened limbs of deciduous trees, particularly hickories, maples, and elms (Schiff et al. 2012). The larvae are wood-boring. In Chile, Tremex fuscicornis damages poplar (Populus nigra), as well as Robinia pseudoacacia and Acer negundo (Parra 2007).
Females begin laying eggs in mid-August and continue until late September. They lay 2–7 eggs in each oviposition hole. Eggs either hatch within 15–30 days, or overwinter and hatch the following spring. Larval development lasts two or more years in cold temperate regions. Larvae cannot develop without the presence of a wood fungus (Schiff et al. 2012). In Canada, new adults start to emerge in mid-August, peak in early September, and end in early October. Males emerge about one week before the females.
Megarhyssa macrurus, the giant ichneumon wasp, parasitizes Tremex columba. It searches for Tremex larvae in their tunnels and when it locates one it lays an egg next to it, and then stings the larva to paralyze it.
Tremex fuscicornis, a species native to Eurasia was accidentally introduced into central Chile (Baldini 2002) and is now found in Canada and Australia as well.