Diplolepis spinosa

(Ashmead, 1887)

many-spined twig gall wasp

Diplolepis spinosa is a cynipid gall wasp native to North America that induces large, conspicuous, multichambered stem galls on wild and domestic roses. The has been documented on Rosa blanda, Rosa acicularis, and Rosa rugosa, and has recently become established on domestic roses in central Canada. Its galls are among the most visible in grassland across the continent. The exhibits complex gall development involving deposited in slits between leaf primordia near bud tips, with larvae inducing separate chambers within spherical stem galls.

Pronunciation

How to pronounce Diplolepis spinosa: /ˌdɪp.loʊˈliː.pɪs spɪˈnoʊ.sə/

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Identification

The can be distinguished from other Diplolepis species by its large, spherical, multichambered stem galls with numerous spines, which are described as "one of the most conspicuous" galls in North American grasslands. D. spinosa galls contain lower concentrations of nitrogen and most mineral nutrients compared to D. triforma galls. The galls are structurally more complex and intricate than those of basal cynipid lineages such as Aulacidea hieracii. Gall anatomy includes specialized nutritive , vascular tissues, and sclerenchyma. are deposited singly in slits between leaf primordia with one end touching the procambium, rather than in sticky clusters.

Habitat

Grasslands and areas supporting wild rose . Found on stems of wild roses (Rosa blanda, Rosa acicularis) throughout central Ontario, Canada, and recently established on domestic shrub roses (Rosa rugosa).

Distribution

North America. Documented in Canada: Alberta, British Columbia, Manitoba, and Ontario. Native range includes grassland regions of the continent where roses occur.

Diet

Larvae develop within stem galls on roses, feeding on gall tissue. Specific dietary components beyond gall tissue are not documented.

Host Associations

Rosa blanda - gall induction on stemswild rose, primary native in central Ontario
Rosa acicularis - gall induction on stemswild rose
Rosa rugosa - gall induction on stemsdomestic shrub rose, recently colonized in central Canada

Life Cycle

Exhibits typical of Cynipidae: a bisexual spring with winged of both sexes, and an agamic () generation with wingless parthenogenetic females that emerge in late autumn or winter. Gall development proceeds through growth and maturation phases with seasonal decreases in nutrient concentrations. Spring galls are soft, small, and inconspicuous; the large hard galls visible to observers are produced by the spring bisexual generation and yield the asexual winter generation.

Behavior

females deposit in slits between the base of leaf primordia near the tips of leaf buds, with one end of the egg touching the procambium. Freshly hatched larvae enter cavities that form beneath each egg and induce separate chambers within the developing gall. The does not concentrate organic nitrogen or mineral nutrients in its galls; instead, it regulates nutrient distribution such that gall concentrations remain lower than in healthy tissues. Absolute quantities of minerals in gall tissues correlate positively with the number of inhabitants, indicating nutrient transport to galls is driven by individual action rather than plant response.

Ecological Role

Galls serve as for of ; parasitoids of D. spinosa have mineral compositions similar to their larvae, and does not alter nutrient concentrations or quantities within galls. Gall induction alters host plant mineral nutrient distribution, concentrating higher levels of Cu, Zn, Fe, Mn, and Ni in galls, attached stems, and associated leaves compared to normal tissues. This nutritional alteration causes plant stress that increases vulnerability of roses to attack by other pestiferous insects. Galls may also host —other insects that exploit gall resources without affecting gall wasp offspring survival.

Human Relevance

Considered a pest of domestic roses due to the stress galls cause, which increases plant vulnerability to other pestiferous insects. Gall removal or control is recommended in horticultural settings to prevent secondary pest problems.

Similar Taxa

Diplolepis triformaAlso induces stem galls on wild roses, but D. triforma galls and larvae contain greater concentrations of nitrogen and most mineral nutrients than D. spinosa galls and larvae.
Diplolepis rosaeEuropean that produces "Mossy Rose Galls" on roses; introduced to North America, produces different gall .
Aulacidea hieraciiBasal cynipid lineage that induces structurally simpler, less intricate galls on herbaceous plants (Hieracium) compared to the complex, intricate galls of D. spinosa on woody roses.

More Details

Gall Classification

D. spinosa galls represent the "rosids" type—developmentally and anatomically complex galls on woody plants—contrasted with "asterids" (simple galls on herbaceous plants) as proposed in comparative studies.

Historical Note

Cynipidae, the gall wasp to which D. spinosa belongs, was studied extensively by Dr. Alfred C. Kinsey early in his career before his famous work on human sexuality.