Observations of extrafloral nectar feeding by predaceous and fungivorous mites

2 Pages·1993·0.92 MB·

by  R W Pemberton

5
PROC. ENTOMOL. SOC. WASH.
95(4), 1993, pp. 642-643
Note
Observations ofExtrafloral Nectar Feeding by
Predaceous and Fungivorous Mites
The value ofpredaceous mites as agents tree base. Two mites ran rapidly over the
for reducing the populations ofplant-feed- surfaces of several leaves, then stopped at
ing mites is significant (McMurtry et al. the extrafloral nectaries to feed. The third
1970. Hilgardia 42: 331-390). Many plants mite was feeding at a gland when first no-
have evolved ways to attract and maintain ticedand,afterabouttensecondsoffeeding,
these important predators. Leaves ofsome it also began to run. Later in the season
plantsbeingattackedbyspidermitesrelease (October 23), two other Anystis mites were
volatilechemicalstoattractpredatorymites seen feeding at the extrafloral nectaries on
and help them locate prey (Dicke and Sa- the petiole-blade junctions on some young
belis. 1988. NetherlandsJournalofZoology leavesofsaplingPopulustomentiglandulosa
38: 148-165). Other plants employ leaf T. Lee, also growing in Seoul. These mites
domatia as a means ofenhancing the pres- behaved in a similar manner to those ob-
ence and abundance of predaceous mites served on P. sargentii, runningrapidly over
and fungivorous mites. Leaf domatia are the leaf surfaces, stopping for a period of
hair tufts, pits or pockets located at the leaf feeding, and then running again. The time
vein junctions of many plants that act as spent feeding is estimated to have been 1
sheltersandnurserysitesforthesebeneficial seconds or less at each gland. Usually only
mites(PembertonandTurner. 1989. Amer- oneofthelarge, pairedglandswasfedupon.
ican Journal of Botany 76: 105-112; Theobservationswerefacilitatedbythelarge
O'Dowd and Willson. 1989. Biological size (2-3 mm) and red color ofthese mites,
JournaloftheLinneanSociety37: 191-236). and the prominently placed, large nectaries
Leavesbearingleafdomatiahavebeenfound of the poplar and cherry. Since the mites
to have more predaceous mites than leaves were immature and not identifiable to spe-
that do not have leafdomatia (Walter and cies, it is unknown whether they belong to
O'Dowd. 1992. Environmental Entomolo- one or more Anystis species.
gy 21: 478-484). On August 10, 1990, while observing ex-
Extrafloral nectaries are sugar secreting trafloral nectaries on a Paulownia tomen-
glands (found primarily on leaves) which tosa(Thunb.) Steud. (Scrophulariaceae)leaf
have been shown by many studies to pro- (from a tree growing in Seoul), under the
mote a food for protection mutualism be- dissecting microscope, I noticed many
tween plants and ants (Beattie. 1985. The Czenspinskia sp. (Oud.) (Winterschmidti-
Evolutionary Ecology of Ant-Plant Mutu- idae) feeding at the glands. The extrafloral
alisms. Cambridge University Press, Cam- nectaries of P. tomentosa leaves are tiny
mm
bridge). This note is the first report of ex- spherical cups, about 1 in diameter,
trafloral nectar feeding by predaceous and locatedalonganduponthebasesoftheveins
fungivorous mites. on the uppersurface andbetween the major
OnJuly 27, 1990, threered-coloredmites vein junctions on the lower surface. The
of the genus Anystis (Anystidae) were ob- nectarfeedingmitesstoodontheirhindlegs
served to feed on the extrafloral nectaries on theleafsurface adjacenttotheglandand
ofPrunussargentiiRehdergrowingin Seoul, leanedagainstthe lipoftherim ofthegland
South Korea. The nectaries involved were with theirforelegs, enablingtheirheadsand
on the leafpetioles ofsucker growth at the mouth parts to reach the nectar within the
VOLUME NUMBER
95, 4 643
cup. The mites fed eitheralone or in groups ton. 1990. Korean Journal of Ecology 13:
ofup to four individuals at a single gland. 251-266). Extrafloral nectar is probably
This feeding was observed only at the nec- particularly valuable during the absence of
taries located on the bottom surface ofthe prey and may serve to maintain these pred-
A
leaf totalofabout20miteswereobserved atory and fungus eating mites on the plants
engaged in this nectar feeding during an or in the habitat until prey becomes avail-
hour's observation. During this time the able.
mites moved between glands, walking up In addition to ants, many other preda-
and overemptyglands and stoppingto feed ceous and parasitic arthropods are frequent
at the glands with nectar. visitors to extrafloral nectaries, including
On September 9, 1992, I observed a P. parasitic Hymenoptera (Hespenheide. 1985.
tomentosa leafwhich had many Czempin- Ecological Entomology 10: 191-204) and
skia walking around and on top of empty coccinellid beetles (Pemberton and Van-
nectaries. From an adjacent tree I found a denburg. 1993. Proceedings of the Ento-
leafwith many actively secreting nectaries mological Society ofWashington 95: 131-
but no Czenspinskia. I placed the under- 151). These insects might also cause reduc-
sides ofthese two leaves together, set them tionsintheinsectherbivoresattackingplants
on a lab bench and pressed them together that bear the glands. Research is needed to
with a heavy book. After one hour, I ex- determine the frequency ofextrafloral nec-
amined the leaf with active nectaries and tar feeding by beneficial mites, and what its
noted that large numbers ofthe Czenspin- significance may be for both the mites and
skia had transferred to this leaf and were the plants. Extrafloral nectarfeedingbypre-
feeding at many of the nectaries. Most of daceous mites could prove to be ofconsid-
the mites were feeding at the glands, fre- erable importance in pest management.
quently in groups ofthree to five per gland. Many economic plants, such as cotton and
The value of extrafloral nectar to these stonefruits {Primus spp.), bear extrafloral
mites is probably primarily as an energy nectaries, and predaceousmitesareincreas-
source, but it could have additional nutri- ingly important biological control agents.
tional value since most extrafloral nectars I thank R. L. Smiley (Systematic Ento-
containmanyaminoacids(Bakeretal. 1978. mology Laboratory, USDA-ARS, Belts-
BotanicalGazette 139: 322-332). Sincemost ville, MD) foridentifyingtheAnystis\ H. A.
extrafloral nectaries function on young Denmark (Florida Division ofPlant Indus-
growth and usually cease secretion after try, Gainesville) for identifying the Czen-
leaves reach their full size and harden, the spinkia\ G. W. Krantz (Department ofEn-
availabilityofextrafloral nectartothemites tomology, Oregon State University) and J.
wouldbe mainly in the spring. Theextraflo- A. McMurtry (Department ofEntomology,
ral nectaries ofP. tomentosa are an excep- University ofCalifornia, Riverside) for re-
tion to this generality because they often viewing an earlier version ofthis note.
continue to function in older leaves. Plants
Robert W. Pemberton, Asian Parasite
growing under irrigation or in areas with
Laboratory, United States Department of
rainysummers, suchas Korea, haveenough
Agriculture, Agricultural Research Service
moisture for new growth of foliage in the %
(Seoul, Korea), American Embassy, Unit
summer and autumn, making the period of #15550, APO AP 96205-0001, U.S.A.
nectar availability much longer (Pember-