The Biology of Coastal Sand Dunes M. Anwar Maun - Inecol

urrows along the sea coasts in many areas of
the dunes. Their impact on vegetation is usually
minimal.
10.5 Insects and their impact
on vegetation
Shelford (1977) found many species of invertebrates:
the white tiger beetle (Cicindela lepida),
bronze tiger beetle (C. scutellaris), sand spider
(Trochosa cinerea), burrowing spider (Geolycosa
pikei), white grasshopper (Trimerotropis maritime),
long-horned locust (Psinidia fenestralis),
sand locusts (Ageneotettix spp., Spharagemon
spp.), migratory locusts (Melanoplus spp.), digger
wasps (Microbembex monodonta) and ants
(Lasius spp.) in the open dune, grassland-heath
vegetation and dry forest in the Chicago region
(Shelford 1977). Some ant species tend aphids
by storing and guarding their eggs over winter,
hatching them and then placing them on
preferred food plants. Ant lions (Cryptoleon
spp.) are common in coastal sand dunes. They
build conical pits in sand and wait at the bottom
for an unsuspecting prey to fall into it.
The mesophytic forest also contains numerous
species of invertebrates: most characteristic
(Shelford 1977) are the green tiger beetle
(Cicindela sexguttata), millipedes of genera
Fontaria and Spirobolus, centipedes of genera
Lithobius and Geophilus, betsy beetles (Passalus
spp.), woodroaches (Blattidae spp.) and wood
snails (Cepaea spp.).
A tally of insects grazing on Cakile edentula
showed that the plants were palatable to a
large number of both generalist and specialist
species. Cutworms (Euxoa spp.; Family
Noctuidae; Order Lepidoptera) fed on roots
and cut off stems either at or below the sand
surface. In one study about 9% of the seedlings
were lost in 1979 (Payne and Maun 1984).
Cabbage butterfly (Pieris rapae; Family Pieridae;
Order Lepidoptera) larvae consumed leaves of
seedlings and killed them. Banded-wing
grasshoppers (Trimeroptropis verraculatus;
Family Acrididae; Order Orthoptera), chewed
large parts of leaves thus decreasing the leaf
ANIMAL–PLANT INTERACTIONS 157
area and photosynthesis. Flea beetles
(Phyllotreta cruciferae and P. striolata; Family
Chrysomelidae; Order Coleoptera) were also
very serious pests of this species. The insects
rasped small pits in the foliage, chlorophyll
was lost and seedlings died. The diamondback
moth (Acrolepia xylostella; Family
Plutellidae; Order Lepidoptera) caused minor
damage by eating from the underside of leaves
and producing many small holes. Snout beetles
(Hypera postica and H. nigrirostris) were
particularly abundant on cold windy days and
fed on cotyledons of young seedlings in early
spring. Aphids (Hyadaphis erysimis; Family
Aphididae; Order Homoptera) infested about
37% of Cakile plants on the beach in July of
each year and caused curling of leaves and
stunting of stems. Ladybird beetles did exert
some control on aphid populations but their
numbers were small.
Many insects have been reported to damage
Ammophila breviligulata (Maun and Baye
1989). Aphids infected the apical meristems
and a beetle (Strigoderma arboricola) entered
the open florets and consumed both the male
and female parts of the flower and developing
seeds. A soft scale insect (Eriococcus caroliniae),
was a serious pest that consumed
leaves and sheaths of plants. Caterpillars of
the family Danaidae consumed all parts of
A. breviligulata including the glumes, lemma
and palea. Other insects of minor importance
consisted of a gall midge (Mayetiola ammophilae),
a moth (Chenoriodes arenella), a bug
(Phyllophaga rugosa), banded-wing grasshopper
(T. verraculatus) and nematodes. In
Lithospermum caroliniense the insect damage
was primarily caused by larvae of Ethmia
longimaculella that constructed webs around
the cymes of stems and consumed leaves and
flowers inside the webs (Westelaken and
Maun 1985a). Approximately 8–17% of the
flowers per plant on the first dune ridge at the
Pinery were consumed. Tent caterpillars
(Malacosoma americanum) are a common sight
on Prunus virginiana in spring of each year
and may completely defoliate shrubs.