Family common name: cimbicid sawflies
Genus: Cimbex Olivier, 1791
The family Cimbicidae is relatively uncommon and little-studied in North America. However, their large size and aposematic coloring make the family somewhat conspicuous (Taeger et al. 1998). Cimbicidae are robust, with the general shape of a bee, long hairs, and clubbed antennae (Smith 1993).
Cimbex are considered one of the “giant” sawflies because of their large size compared to most other Symphyta. Some individuals in the genus can reach 30 mm in length. The large size and yellow and black striped coloration mimics wasps from the family Vespidae, specifically Vespa spp. (yellowjackets). Males have enlarged mandibles and hind legs. (Vilhelmsen 2019). However, because coloring and size can be variable, sex is most easily determined by the presence or absence of an ovipositor (Smith 1993).
Cimbex can be confused with other Cimbicidae. In North America, they can be distinguished from Abia by the body size and the parallel inner edges of the eyes, and from Trichiosoma by the lack of apical spur on the femora (Taeger et al. 1998).
Cimbex quadrimaculatus is a destructive pest of almond trees in the Mediterranean and Southwest Asia. There are no North American records for this species (Bolu 2016).
In North America, documented hosts for Cimbex include trees from the genera Ulmus (elm), Salix (willow), Alnus (alder), Betula (birch), Tilia (linden), Acer (maple), Populus (cottonwood), Ostrya (hop-hornbeam), and herbaceous plants of Lonicera (honeysuckle) (Smith and Middlekauff 1987, Smith 1993). Survey records indicate that C. americana will also feed on Malus (apple) and Prunus (plum) (Stein 1974).
Cimbex larvae feed externally on foliage. The larvae are caterpillar-like, usually green or gray with dark spots or striping, and can be recognized by the one-segmented antennae and tarsal claws on each of the five-segmented thoracic legs. Mature larvae can measure up to 50 mm in length, making them among the largest sawflies (Smith and Middlekauff 1987).
Larvae disturbed by predators react by excreting a clear defensive liquid, a behavior called “reflex bleeding”, then fall to the ground, where they become difficult to see. Mature larvae drop to the soil and build a cocoon in leaf litter, within which the prepupae overwinter. After pupation, the adult chews a circular hole in the cocoon and emerges (Liston and Späth 2006, Harizanova et al. 2012).
Adults also feed and in some cases will use their mandibles to wound the wood of trees and feed on exuded sap. Male adults are known to fight one another for access to females using their expanded mandibles and hind femora (Vilhelmsen 2019). Cimbex are univoltine (Smith and Middlekauff 1987).
Though not exotic, Cimbex americana, also known as the “elm sawfly” can be highly destructive to both elm and willow trees. Eggs are laid up to 12 per leaf, so larvae can defoliate entire canopies. This species is common in the Northeast, Midwest, and Northwest United States, and in Canada as far north as the Yukon Territory. Populations are also recorded in Texas, Florida, Colorado, and New Mexico (Stein 1974).
World: This genus occurs throughout Asia, Europe, and North America (Taeger et al. 2010).
Map data from: GBIF.org (26 June 2019) GBIF Occurrence Download Cimbex
Details about data used for maps can be found here.