''Adelges'' is a genus of insects which feed on

conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

s. Excepting galls formed by the spruce gall midge, galls are caused by aphid-like insects of the superfamily Phylloxeroidea (family

Adelgidae The Adelgidae are a small family of the Hemiptera closely related to the aphids, and often included in the Aphidoidea with the Phylloxeridae or placed within the superfamily Phylloxeroidea as a sister of the Aphidoidea within the infraorder A ...

) commonly known as the spruce gall adelgids. They have complex life cycles, some species feeding exclusively on

spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ( taiga) regions of the Earth. ''Picea'' is the sole genus in the sub ...

, others feeding on spruce and an alternate

. However, galls characteristic of each species are formed only on spruce. Six generations are usually needed to complete the 2-year cycle, and in the case of species having an alternate host, winged adults about 2 mm long are formed only in the generations that move from one host to the other. The spruce gall adelgid (''Adelges lariciatus'' Patch) occurs in alternate years on spruce and larch from Alberta to the Maritimes and in adjacent parts of the United States. The pale spruce gall adelgid (''Adelges strobilobius'' Kaltenbach) has a similar range but prefers

black spruce ''Picea mariana'', the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of the province of Newfoundland and La ...

red spruce ''Picea rubens'', commonly known as red spruce, is a species of spruce native to eastern North America, ranging from eastern Quebec and Nova Scotia, west to the Adirondack Mountains and south through New England along the Appalachians to wester ...

white spruce White spruce is a common name for several species of spruce (''Picea'') and may refer to: * '' Picea glauca'', native to most of Canada and Alaska with limited populations in the northeastern United States * '' Picea engelmannii'', native to the ...

. Species include: * ''Adelges abietis'' ( Pineapple gall adelgid) * ''Adelges cooleyi'' (

Gall adelgid The gall adelgid (''Adelges cooleyi'') is an adelgid species that produces galls in spruce trees. They infect the new buds of native spruce trees in the foothills of the Rocky Mountains in the spring. They also attack blue spruce to a lesser ...

) * ''Adelges piceae'' (

Balsam woolly adelgid Balsam woolly adelgids (''Adelges piceae'') are small wingless insects that infest and kill firs, especially balsam fir and Fraser fir. They are an invasive species from Europe introduced to the United States around 1900. Because this species ...

) * ''Adelges tsugae'' (

Hemlock woolly adelgid The hemlock woolly adelgid (; ''Adelges tsugae''), or HWA, is an insect of the order Hemiptera (true bugs) native to East Asia. It feeds by sucking sap from hemlock and spruce trees (''Tsuga'' spp.; ''Picea'' spp.). In its native range, HWA ...

)

References

Bugguide.net. Genus ''Adelges''
Adelgidae Sternorrhyncha genera {{Sternorrhyncha-stub