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LEPIDOPTERA, Lycaenidae -- <Images> & <Juveniles> This family is of interest to biological control because of the
large number of species that are predaceous.
The subfamilies Gerydinae and Liphyrinae are entirely predaceous, while
some species of Lycaeninae are predaceous as final instar larvae. Early accounts of biology and behavior of
predaceous butterflies were by Farquharson (1922), Clark (1926) and Balduf
(1938). The latter reviewed the
interrelations between lycaenids and the ants and Homoptera with which they
are associated. Species were divided
into 6 classes on the basis of food habits and of their relations with
ants. In many cases the caterpillars
and ants are competitors for a common food supply, and the secretions of
special glands of the caterpillars are a kind of bribe to induce the ants to
tolerate their presence (Clausen 1940/62). Predaceous Lycaenidae usually prey on Coccidae (Pseudococcus) and Aphididae, but also
on Cicadellidae and Membracidae and the immature stages of Formicidae. In North America, Feniseca tarquinius F.
was the first lycaenid found to be predaceous. It fees in all its larval stages only on aphids, such as Prociphilus, Schizoneura, and Pemphigus. Eggs are laid singly among the aphid colonies,
always on the underside of the twig.
The newly hatched larva spins a loose web over its body, beneath the
aphids, that is thought to be for protection. Feeding occurs from underneath. The long hairs of the dorsum of the body entangle a quantity of
waxy material, giving the larva a woolly appearance. The larvae seem quite immune to attack by
ants that tend the aphids. They have
a variable color pattern, due partly to the species of aphid that is
attacked. There are 4 larval instars
and pupation seems to occur in the trash beneath the tree. The egg, larval and pupal stages take 3-4,
10, and 8-11 days, respectively.
There are 3-5 generations annually, and they overwinter as pupae
(Edwards 1886, Clark 1926). Different species of Spalgis
are most often found as predators of mealybugs, although they also attack
aphids. S. epius Westw. (Aitken
1894) of Asian tropics, lays its eggs among the masses of mealybugs. The flattened, greenish larvae bear a
fringe of bristles about the sides and front of the body, and this is used in
shoveling the waxy covering of the host onto its back. This covering gives it a resemblance to
the host individuals, although the older caterpillars are much larger and
resemble syrphid larvae. Only the
younger host stages are attacked.
Larvae are found within ant nests, feeding on mealybugs which are
being held therein. The pupae of Spalgis and Feniseca are peculiar by having a color pattern that is looks
like the face of a monkey. The larvae
of some Lachnocnema spp. are
associated with Cicadellidae, on which they are predaceous. They also feed somewhat on the secretions
of the leafhoppers, and may possibly be fed by the ants. Clausen (1940) noted that the genus Lycaena is particularly interesting because of the interrelations
developed between its members and their ant hosts. Oviposition is thought to occur mainly on food plants beneath
which ant colonies are situated. The
young larvae are entirely plant feeders, but in the last stage they find
their way or are carried into the ant nest where they feed on ant larvae and
pupae. A pronounced cannibalistic
habit is shown by the larvae during the plant-feeding period, which is
entirely absent after entry into the ant nest. In these species, the last instar larvae are equipped with a
special gland on the dorsum of the 10th segment, from which is secreted a
clear, liquid substance that is attractive to ants. The 3rd instar larvae of L.
arion do not evacuate the hindgut
until right before pupation, which differs from the normal in Lepidoptera,
but resembles Hymenoptera. Clark
(1926) examined the excrement to find many dermal hairs and mandibles of Myrmica, thus establishing
predation. Pupation occurs in
springtime in situ only on thyme, and it is only in the 4th stage that the
larvae enter the nests of Myrmica. The life cycle takes one year of which 10
months represents the larval period.
All of this, with the exception of the first 2 weeks, is in an ant
nest. Larvae in the subfamily Gerydinae feed entirely on other insects,
particularly Homoptera. Gerydus chinensis Feld. is found most often among aphids, and the larvae
are thought to consume ca. 20 individuals per day (Kershaw 1905). The prey are often seized with the
forelegs and held in the air while being consumed. The eggs are laid directly among the aphids and the ants who
attend them, and the female sometimes even thrusts them aside with her
ovipositor during oviposition. Megalopalpus zymna D. & H. (Lamborn 1914) differs in that it is associated
intimately with ants of the genus Pheidole
during development. However, the
larvae's food, nymphs of Cicadellidae and Membracidae, is enclosed within the
ant shelters. The female butterfly
lays her eggs singly in the area of such shelters as contain the proper
hosts. Sometimes she may place them
directly on an egg mass or on the host body.
The act of attacking a host reveals an interesting adaptation whereby
capture is readily accomplished. The
larva approaches the host with its legs raised and vibrating and causes them
to caress the wings of the latter, thus stimulating the ministrations given
by the ants with their antennae (Clausen 1940). Finally the head attains a position directly over the body,
after which the prey is seized between the legs and feeding occurs at a point
just behind the head. The prey may
ultimately also be raised into the air.
Both nymphs and adults are attacked, although the former are more
common. The larva of Megalopalpus is protected by a hard
integument which is studded with tubercles surmounted by coarse hairs. The ants derive no benefit from their
presence in the shelter and thus are not attentive. The adult butterflies have the habit of feeding on the body
secretions of the same hosts, rather than on nectar and honeydew. They probe the body with the proboscis and
apparently derive some nutritional value from the secretions. They have also been found to do likewise
on the plant surface on which the hosts rest (Clausen 1940/62). Numerous modification in the predaceous mode of life are shown by
species of Liphyrinae. Liphyra brassolis F. caterpillars feed on the larvae of the green tree
ant, Oecophylla smargdina F. in Australia (Dodd
1902). The eggs are usually laid in pairs
on the branches or trunks of trees containing ant colonies, and the young
larvae make their way into the nest.
They seem to move from nest to nest while feeding, and pupation occurs
in the host nest. The last larval
skin is not discarded but remains in changed form as an outer covering for
the pupa. The adult moths are covered
with many loose scales that seem held together by an oily substance. This covering is thought to serve as a
protection from the very aggressive host ants, especially during moth
emergence. Euliphyra mirifica Holl., which is found in Oecophylla in Africa, does not appear
to be predaceous, but rather the larvae are fed by the ants. The species of the genus Aslauga are predaceous on Coccidae,
especially the soft scales and mealybugs.
The larvae have a hard integument, covered with tubercles, which
provides protection from ants attending their hosts. This genus was thought to have arisen from
lichen-feeding ancestors, and the change to the coccid-feeding habit has
occurred gradually (Balduf 1938). It
was believed that first the coccids were associated among the lichens and
consumed indiscriminately. Then,
during times when lichen growth was prevented by adverse conditions, the
larvae were confronted with a choice between starvation and feeding on
Coccidae. References: Please refer to <biology.ref.htm>, [Additional
references may be found at: MELVYL
Library ] |