il ' ii - Northern Research Station - USDA Forest Service

INQUILINES have been recorded from several locations in Europe.
Initially, either abiotic (either frost or drought) or biotic
Larvae of inquilines gall midges are phytophagous but (particularly fungi) causes for such damage have been
neither induce galls nor live freely in plant tissue, considered. Gibbs (1982) was the first to provide
Females ofinquiline gall midges lay their eggs on or in evidence that such canker formation is the result of
galls produced by other species---usually gall midges or infestation by the larvae of an undetermined species of A
O
gall wasps. Hatched larvae feed by sucking sap from the gall midge in the genus Resseliella. Females were
tissue of the gall, as do those of gall inducing species, observed to lay eggs in recently formed wounds made by
Nine inquiline gall midge species have been described to the woodpecker Dendrocopus major (Picidae, Aves) _n
date in galls produced by gall midges on oaks. Inquiline oak trunks during the months of July and August.
species are UsUally not as abundant as their gall-inducing
hosts. In 1990, Dengler found thousands of young oak trees in
forest stands near Rottenburg, southern Germany, to be
Galls induced by oak cynipid gallwasps _.lso sometimes severely damaged by these gall midges. Analysis of
contain gall midge larvae. The orange-yellow larvae of morphological characters of the larvae and later also of
ParallelodilJlosis galliperda develop under the asexual reared adults, led us to identify this species as Resseliella
spangle galls of Neuroterus quercusbaccarum, sucking quercivora (Mamaev and Krivosheina 1965). Original
sap from the gall tissues. This alters the shape of the uncertainty with our identification resulted from the fact
galls, which are less regularly circular than unattacked that R. quercivora was described only briefly by Mamaev
galls. Some are so damaged that they fall prematurely, (in Mamaev and Krivosheina 1965) and in the original
leading to the death of the gallwasp larvae (hence the description the host plant and biology are not given. The
name galliperda). Similarly, the larvae of Xenodiplosis injury to oak trees may be derived only from the species
laeviusculi develop under the asexual spangle galls of name "quercivora". The larvae of Resseliella quercivora
Neuroterus albipes. Nothing more is known about the are responsible for the origin of the necrosis on oak
biology of this species, trunks. These necroses only develop secondarily
. following primary damage by woodpeckers or through
Adults ofClinodiplosis cilicrus have been reared from other causes. Females of R. quercivora are probably
galls of two gall wasp species--4he sexual generation attracted to such wounds by olfactory cues present in the
galls of Biorhiza pallida and the asexual generation galls cambium exudate.
of Andricusfecundator. Originally these gall midges
were considered to be separate and named Clinodiplosis Twenty-three gall midge species are included in the
biorrhizae and Clinodiplosis gallicola, respectively. On genus Resseliella Seitner, 1906 in the Palaearctic R_gion
the basis of extensive experiments and an analysis of (Skuhrav_i 1986). Gagn6 (1973) considered the genera
morphological characters of larvae and adults, Skuhrav_i Thomasiniana Strand, 1927, Profeltiella Kieffer, 1912
(1973) demonstrated there is only one species, and Wichmanniella Mrhn, 1955 to be synonyms of
Clino&'plosis cilicrus. It is a phytosaprophage whose Resseliella. Members of this genus usually do not cause
larvaedevelop in decaying plant matter, galls, but are often associated with the resin of conifers
• or with damaged trunks of deciduous trees, where larvae
Two other gall midge species have been reared from the have been found under the damaged bark. Species of this
asexual generation galls of Andricusfecundator. Larvae genus are considered to be host-plant specific. Only
' of Arnoldiola gemmae are probably inquilines between Resseliella oculiperda (RObsaamen), whose larvae have
the scales Of the gall where they pupate in white cocoons, been found between bud grafts and the stock of roses, is
Larvae of Lestodiplosis necans, which in common other also known to occur in similar locations on several fruit
' member of.the genus Lestodiplosis are probably zoopha- tree species in other rosaceous genera, w
gous, attack the larvae of Arnoldiola gemmae.
" Using a knife or die, Dengler intentionally wounded the
All these inquiline gall midge species were found in trunks of 37 host plant species belonging to 12 plant
.Central Europe. only one species of inquiline gall midge families in the arboretum at Rottenburg am Neckar. Gall
is known from the Mediterranean area: adults of midge larvae and necrosis of a form similar to that
Lasioptera nigrocincta were reared from galls of the induced by Resseliella querciperda on oaks were found
cynipid Dryocosmus australis on leaves of Quercus ilex on several other tree species. We are currently trying to
in Algeria. discern whether a single Resse/ie/la species is responsible
for the development of necroses on many host tree
CAMBIUM-FEEDING GALL MIDGES species, or whether several Resseliella-species are
responsible for the development of necrosis on specific
Cambium necroses and bark damage to the trunks of host tree species.
young oaks (sometimes called oak-cancer or T-necroses)