Cimbex

Taxonomy

Order: Hymenoptera
Family: Cimbicidae
Subfamily: Cimbicinae
Genus: Cimbex Olivier, 1790
Common name: cimbicid sawflies

Background

Cimbex is a genus of large-bodied sawflies in the family Cimbicidae. They are relatively uncommon and little-studied in North America. Their large size and yellow- and black-striped coloration in at least one species resembles species of yellowjackets in the genus Vespula.

How to separate from Asian giant hornet

  • Cimbicid sawflies are smaller and are generally only half as large as Asian giant hornets
  • One common native species, the elm sawfly, has several different forms; the black and yellow form appears similar to some wasps and hornets

Distribution

Cimbex species are only found in Eurasia and North America. Four species occur in North America (Taeger et al. 2010).

The distribution of Cimbex sp. by GBIF: https://www.gbif.org/species/1249709

Diagnostic characteristics

  • Adults are 15–30 mm (0.6–1.2 inches) long.
  • The head is large, with large, strong mandibles.
  • The antennae are clubbed.
  • Males have expanded mandibles and spiny legs.
  • These sawflies cannot sting.
  • The larvae are caterpillar-like and can be up to 55 mm (2 inches) long.
  • Larvae have one-segmented antennae, and tarsal claws on each of the five-segmented thoracic legs..

Diversity

There are 17 species of Cimbex.

Host/prey associations

Larval Cimbex feed on leaves of elm (Ulmus), maple (Acer), birch (Betula), willow (Salix), basswood (Tilla), alder (Alnus), cottonwood (Populus), hop-hornbeam (Ostrya), and honeysuckle (Lonicera). Adults girdle bark on twigs during feeding and oviposition (Smith, 1993). These sawflies are not generally considered a forestry problem, but they can defoliate elms and willows when population numbers are high (Stein 1974).

Nesting and general behavior

Larval Cimbex feed on foliage and are often confused with caterpillars. When disturbed, they react by excreting a clear defensive liquid, then falling to the ground. Once the larvae are mature, they will also drop to the ground where they will build a cocoon in the leaf litter. Larvae overwinter as prepupae and pupate in spring (Milne and Milne 1980; Harizanova et al. 2012).

Adult Cimbex typically fly from May to August. They damage trees to cause them to exude sap which the adults will feed on. Though Cimbex americana is a native species, it can cause significant damage to elm and willow trees if there are a large number of larvae feeding on the same tree (Stein 1974).

Known invasives

Palaeocimbex quadrimaculatus (Müller) can be a destructive pest of almond trees in the Mediterranean and southwestern Asia. There are currently no North American records of this species (Bolu 2016).

<p><em>Cimbex americana</em>; photo by dbarronoss, Flickr</p>
<p><em>Cimbex</em> sp.; photo by Frank Vassen, Flickr</p>
<p><em>Cimbex</em> sp.; photo by Ryszard, Flickr</p>
<p><em>Cimbex americana</em>; photo by Nelson, iNaturalist</p>
<p><em>Cimbex americana</em>, dorsal view; photo by Hanna Royals, USDA APHIS PPQ ITP</p>
<p><em>Cimbex americana</em>, lateral view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Cimbex americana</em> (left) compared to <em>Vespa mandarinia</em> (right), lateral view; photos by Hanna Royals and Todd Gilligan, USDA APHIS PPQ ITP</p>