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DIPTERA, Phoridae (Haliday 1851)
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& <Juveniles> Description & Statistics
Megaselia fasciata Fall is a well known
parasitic species of Phoridae. it is gregarious
and internally parasitic of the pupae of many coccinellid genera in Europe
(Lichtenstein 1920, Menozzi 1927).
The number of individuals developing in each host is dependent on the
size, but 8-14 reach maturity in each pupa of Coccinella. The parasitoid
may sometimes act as an important natural control of the increase of these
beneficial beetles, as shown by the fact that a parasitization of 48% has
been noted on Adalia. During oviposition the female stands
transversely on the thorax of the freshly formed pupa and curves the
ovipositor beneath it, and the eggs are laid externally in small clusters
between the legs. Sometimes eggs are
also laid on the bodies of larvae that are approaching the time for pupation. Embryonic development is well advanced at
the time of oviposition, and hatching may occur within 3 hrs. However, Lichtenstein (1920) noted that
external incubation took 1.5 to 2.6 days.
The eggshells fall from the host soon after hatching, and thus there
is no external evidence of attack.
The newly hatched larvae immediately penetrate the body at the base of
one of the legs, and their ensuing development is very rapid. Feeding is completed in 2-5 days, after
which the larvae emerge through an opening between the head and thorax to
enter the soil to pupate. Parasitized
pupae retain their normal form, although in death they assume an erect
position which contrasts to the horizontal position of healthy pupae. Female flies feed on body fluids exuding
from punctures made with the ovipositor, a habit that seems closely
associated with oviposition (Clausen 1940/62). Balduf (1928) found that oviposition of M. aletiae Comst. on Achatodes zeae Harr. usually occurs only when the larvae are sick or
feeble, and the species is thus more a scavenger than a parasitoid. Such larvae enter the body through the
anal opening rather than by penetrating the integument. The mass of larvae that develop causes the
posterior 1/3rd of the host body to be much distended. They enter the body cavity, and the store
of adipose tissue is the principal food source. The larval stage is completed in 11-15 days, and pupation
occurs in the host tunnel. With M. giraudii
Egger, a parasitoid of the grasshopper Phasgoneura
viridissima L. in Europe, an adult
host, fully active at the time of capture, later yielded 12 mature maggots of
Megaselia. These emerged from a large opening in the
integument at the side of the mesothorax.
Dissection of the host remains revealed that the muscular tissue of
the thorax had been completely consumed (Timon-David 1938). Some species of Megaselia
are parasitic on myriapods. Megaselia juli Brues was the first species noted to have this habit. Several instances of groups of females
persistently attacking live individuals were observed by Myers (1934), this
continuing in each case for several hours.
Hosts make strong but unsuccessful efforts to ward off attacks. The phorids always approach with the
ovipositors extended, centering their attention to the head region. Larval development is complete in ca. 3
days, and the body contents of the host are completely consumed by the
maggots. Megaselia cuspidata
Schmitz, in attacking a European myriopod, Iulus sabulosus L.,
oviposits in minute wounds in the integument (Picard 1930). However, the species is a true parasite
because these wounds by themselves would not result in death. Berland (1933) believed that the larvae of
Phoridae attacking ants and myriapods, are able to gain entry to the body
cavity of the host only through wounds.
Hypocera incrassata Meig., is a solitary
internal parasitoid of the larva of the bibionid fly, Bibio marci L. in
England (Morris 1922), solitariness being rare in the family. The mature larva emerges from the dead
host and pupates in the soil. Serious losses are inflicted in apiaries in Brazil through the
attack of Melaloncha ronnai Borgm. on adult bees (Ronna
1936, 1937). Mortality of up to 50%
has been observed, with the highest figures usually being found in apiaries
located in shady and damp areas. The
female lays her egg in the abdomen of the bee. The young larva causes an appreciable displacement of abdominal
organs, but apparently produces no serious injury. It soon migrates into the thorax where it feeds on muscular
tissue and quickly matures.
Parasitized bees have difficulty flying and finally fall to the
ground, walk about irregularly for a time and die. The thoracic tissues are almost entirely consumed, and the head
and prothorax of the bee become detached from the rest of the body or remain
connected with it only at one side.
Pupation occurs most often within the thorax of the dead bee, with the
anterior end of the puparium exposed.
This species is generally solitary, although sometimes two individuals
attain maturity in a single host. The
egg and larval periods are completed in ca. 10 days, and the adult fly
emerges 3-4 weeks later. Ronna (1937)
recommended the use of glass traps containing a soap solution in which dead
bees have been placed to control this phorid. The decomposing mass is attractive to Melaloncha adults. Although many species of Phoridae are associated with ants in
various ways, only the parasitic species are herein discussed. These are included in a large number of
genera, of which Plastophora is
most common. Borgmeier (1928, 1931)
listed the species of 5 genera known to parasitize ants of the genus Atta and related forms. All are characterized by a pronounced
development of the ovipositor, this being extreme in Myrmosicorius (Clausen 1940/62).
Apocephalus pergandei Coq. is a solitary internal
parasitoid of carpenter ant workers, Camponotus
pennsylvanicus De G. (Pergande
1901). The female fly jumps on the
ant in the open and lays the egg on its head. The young larva then enters through the occipital foramen. Feeding is confined to the contents of the
head, which is completely hollowed out and detached from the body. Pupation also occurs within the head
cavity. Fox (1883) probably observed
this species also, for the host species and larval habits are identical. The adult fly was not secured in that
study. Megaselia conica
Malloch was reared from the abdomen of C.
pennsylvanicus (Clausen 1940). Wasmann (1918) made extended observations on Plastophora species. He
described the association of P. formicarium Verr. with Lasius spp. It is also known to attack Myrmica
and other genera in Europe. The adult
flies hover, sometimes 50-60) over the ant nest, or at any points where the
ants congregate, and are seemingly attracted by their odor. Only worker ants are attacked, the winged
males and females being ignored.
Also, dead or injured ants lose their attractiveness, and the species
is thus not a scavenger. The female
pounces on the worker from the air, the latter making a determined effort to
escape or to defend herself. After
alighting, the parasitoid persistently follows in the rear of the ant, always
centering her attention on the abdomen.
She finally pounces on her prey and presumably inserts the ovipositor
dorsally between the abdominal segments (Clausen 1940/62). Plastophora crawfordi Coq. and P. spatulata
Malloch attack the fire ant, Solenopsis
geminata F., workers in
Mississippi. The female strikes the
ant from above with great rapidity, seemingly in the anterior portion of the
body. The prey falls on its side and
is stunned or paralyzed for several seconds.
It is thought that these species are parasitic, but they have not been
reared from this host. Almost identical
habits were found in Plastophora
sp. attacking Camponotus in Europe
by Fage (1933). The parasitic
relationship between Plastophora
and ants has been generally accepted by various researchers, and P. formicarium
in particular has received attention.
The activities of the female flies and the form of the ovipositor
certainly lead one to believe that there attack is for purposes of
oviposition directly into the body of worker ants. However, Clausen (1940) noted that no proof of this was
available. The larvae were not taken
from the bodies of ants, nor have the pupae been found under conditions that
would definitely establish the relationship. There are relatively few predaceous Phoridae, and those which are
known to develop on the eggs of other insects and spiders. Termitoxenia
spp. reportedly feed on termite eggs, while Megaselia epeirae Brues
was reared from the egg sacs of spiders (Malloch 1912). An undetermined species was found in a
very large port of the egg sacs in Japan, some containing up to 200-300
larvae and puparia. Autuori (1928) and Fonseca & Autuori (1938) studied the
biology and behavior of Syneura cocciphila Coq. (= infraposita
B.S.). Autuori
stated that this species was a gregarious internal parasitoid of the adult
females of Icerya, but this was later
found to be in error as its true status as an egg and larval predator was
found. A maximum of 55 individuals
can develop to maturity on the contents of one egg sac. Although feeding is mostly on the eggs,
the maggots also attack young larvae during the time they remain within the
sac. Larvae develop rapidly, and
pupation occurs mostly inside the sac. Phoridae are a large cosmopolitan family, with over 3,000
species. They are especially diverse in the tropics. Important morphological characters include
a short antenna, 2 basal segments small, 3rd segment globular; wings (when
present) with narrow triangle of heavy veins (S-c and R) in humeral area,
extending along costal margin; branches of M and Cu parallel, weakly
developed. The thorax is large,
bristly and humpbacked. Many of the
parasitic species possess a long, heavily chitinized ovipositor (Clausen
1940). The body is minute to small,
and adults move with characteristic short, jerky movements. Phoridae are primarily scavengers on decaying animal and
vegetable matter or are scatophagous.
Larvae and pupae of several species have been taken from mole
nests. The myrmecophilous and
termitophilous genera and species include the more degraded representatives
of the family (Clausen 1940/62). Some develop as predators in egg masses of
spiders and acridids. Entomophagous
species exhibit a wide diversity in hosts.
Most of the parasitic species are primary, solitary, endoparasitoids;
a few species develop gregariously.
Many of the parasitic species attack ant pupae and adult. Some species parasitize coccinellid pupae,
larvae and pupae of Lepidoptera, larvae of Diptera, adult bees or
myriapods. Those of predaceous habit develop
on the eggs of spiders and locusts. Syneura cocciphila Coq. in South American and the West Indies, attacks
eggs of the cottony-cushion scale, Icerya
purchasi Mask. Several species have been found in egg
cases of Locusta migratoria L. Complete records of the food and host preferences for the family
at the time were given by Malloch (1912).
The division between the scavengerous and parasitic habits is not
distinct; a species may develop in either way, or it may attack living
organisms that, while still living, are in an unhealthy condition or are
wounded and will soon die. Therefore,
a species can seldom be considered as parasitic in the absence of
experimental proof (Clausen 1940/62).
Economically, the entomophagous Phoridae must be classed as
predominantly injurious rather than beneficial, because of their general
attack on coccinellid pupae, adult bees, and spider eggs. One truly beneficial species is S. cocciphila,
a common enemy of the cottony-cushion scale. They have not been used successfully in biological pest
control. References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] Brues, C. T.
1915. Wisconsin Nat. Hist.
Soc. Bull. 12: 85-152. Brues, C. T. 1950. Connecticut St.
Geol. Nat. Hist. Sur. Bull. 75:
33-85. Cole, F.
R. 1969.
The Flies of Western North America.
Univ. Calif. Press, Berkeley & Los Angeles. 693 p. Colyer, C. N.
1957. A new species of Plastophora (Dipt. Phoridae) from
England: a short discussion of the evolution of the present concept of the
genus and a key for the identification of the world species. Brotéria 26: 75-87. Malloch, J. R.
1912. Proc. U. S. Natl. Mus.
43: 411-529. Menozzi, C.
1927. Bol. Ital. Ent. Soc. 59: 72-8. |