Hemiptera

The Hemiptera are a large order of insects that are highly variable in appearance and include many pests of importance to plant health. There are six major suborders, but only three containing members that are common tree pests: Auchenorrhyncha, Heteroptera, and Sternorrhyncha. Aphids, adelgids, hoppers, cicadas, scale insects, spittlebugs, and true bugs are some of the commonly encountered members of this order that feed on trees.

Morphological characteristics of these insects:

• adults usually have two pairs of wings, although some aphids and adelgids have phases in which the adult is wingless;
• the front portion of the forewings of adult Heteroptera (a suborder) is hardened and often brightly coloured forming a protective covering, while the hind portion of the forewings and both hindwings are membranous;
• when wings are present in the suborders Auchenorrhyncha and Sternorrhyncha, both pairs are membranous; and
• the mouthparts are adapted for piercing and sucking, and the elongated beak-shaped mouthparts (rostrum) lie under the body when the insect is at rest.

General biology and ecology

Hemiptera develop by incomplete metamorphosis (hemimetabolous development), where the immature stages, called nymphs, resemble smaller versions of the adults but with less developed, nonfunctional wings. Immature stages and adults typically feed on the same resources, and all use piercing mouthparts to penetrate their food source and suck liquids from their host. Plant-feeding species such as aphids, adelgids (e.g., eastern spruce gall adelgid), and scale insects (e.g., oystershell scale) often have complex life cycles, alternating between two different host plants and producing different forms depending on the particular host plant and/or season. In many cases there are no males, at least for part of the season, and females reproduce without fertilization (parthenogenesis). Most species are active or flying during the day (diurnal) or at dusk (crepuscular).

Important families in the order Hemiptera that contain tree pests

Listed below are families from this order found in this database. Species listed within the families are linked to the site’s pest fact sheets.

Adelgidae (adelgids or pine and spruce aphids)

• Balsam woolly adelgid
  Scientific name: Adelges piceae (Ratzeburg)
  • Revision 2024
• Cooley spruce gall adelgid
  Scientific name: Adelges cooleyi (Gillette)
  • Revision 2024
• Eastern spruce gall adelgid
  Scientific name: Adelges abietis (Linnaeus)
  • Revision 2024
• Hemlock woolly adelgid
  Scientific name: Adelges tsugae Annand
  • Revision 2025
• Pine bark adelgid
  Scientific name: Pineus strobi (Hartig)
• Pine leaf adelgid
  Scientific name: Pineus pinifoliae (Fitch)

Aphididae (aphids or plantlice)

• Aphids (plant lice)
  Scientific name: Aphis sp.
• Balsam twig aphid
  Scientific name: Mindarus abietinus Koch
• Green spruce aphid; spruce aphid
  Scientific name: Elatobium abietinum (Walker)

Cercopidae (froghoppers or spittlebugs)

• Pine spittlebug
  Scientific name: Aphrophora cribrata (Wlk)

Cicadidae

Coccidae (soft scales, wax scales, and tortoise scales)

• Pine tortoise scale
  Scientific name: Toumeyella parvicornis (Cockerell)
• Spruce bud scale
  Scientific name: Physokermes piceae (Schr.)

Diaspididae (armoured scales)

• Juniper scale
  Scientific name: Carulaspis juniperi (Bouché)
• Oystershell scale
  Scientific name: Lepidosaphes ulmi (L.)
• Pine needle scale
  Scientific name: Chionaspis pinifoliae (Fitch)

Eriococcidae (felt scales)

• Beech scale
  Scientific name: Cryptococcus fagisuga Lindinger

Miridae (plant bugs)