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COCKROACHES Blatella germanica (L.), Blatta orientalis L., Periplaneta americana (L.), Periplaneta fuliginosa (Serville) & Supella longipalpa
(F.), --Orthoptera, Blattidae & Blattellidae (Contacts) ----- CLICK on Photo to enlarge & search for Subject Matter with Ctrl/F. GO TO ALL: Bio-Control Cases
Predation and parasitization of cockroaches has been observed by several
authors (Ebeling 1975), but there is still little evidence to indicate that
natural enemies are able to reduce or maintain cockroach densities beneath
annoyance thresholds. Nevertheless,
there is a potential for classical biological control and a requirement for
serious consideration of biological control (Piper & Frankie 1978). Hymenopteran egg parasitoids seem to offer
the best potential for short and long term population regulation (Piper et
al. 1978). Inundative releases have a
lot of potential for control both indoors and outdoors (Piper & Frankie
1978). Piper & Frankie (1978)
suggest that a complication with the use of natural enemies for cockroach
control is that not all species are amenable to indoor parasitoid releases;
and Edmunds (1957) reported that cockroach parasitoids may be more annoying
in the home than the oriental cockroach host itself.
Two species of ampulicid wasps, Ampulex compressa
(F.) and Dolicurus
stantoni (Ashmead) are
thought to play a significant role in controlling some species of cockroaches
in Hawaii (Pemberton 1948). The egg
parasitoid, Comperia
merceti (Compere) has
potential for use in biological control.
This parasitoid seems to have a significant impact on brownbanded
cockroach when densities of oothecae are high (Coler et al. 1984). At lower densities parasitization rates
are low. Therefore inoculative or
inundative releases may be necessary to achieve satisfactory levels of
control at lower densities. Comperia merceti has been used for brownbanded cockroach control
with great success (Slater 1980).
The egg parasitoid, Tetrastichus hagenowii
(Ratzeburg) is also believed to be important in the natural control of
cockroaches (Cameron 1955).
Parasitization of P. americana oothecae has attained
83% when parasitoids were released into a room with high host densities (Roth
& Willis 1954). Fleet &
Frankie (1975) and Piper et al. (1978) found significant mortality of
oothecae of American and smokybrown cockroaches due to parasitization by T. hagenowii. History
LeBeck (1985) reviewed natural control of cockroaches, pointing out
that Hymenoptera which were associated with cockroaches as either parasitoids
or predators are found in the families Ampulicidae, Evaniidae and the
chalcidoid families Encyrtidae, Eulophidae, Eupelmidae and Pteromalidae (Roth
& Willis 1960). Most species are
parasitoids of cockroach oothecae, while members of the Ampulicidae are
predators of cockroach nymphs. The
earliest observations of natural enemies of cockroaches were recorded in the
mid 1770's when naturalists such as Ferchauld (1742) noticed the stinging and
predatory behavior of an Ampulex
sp. wasp. The evaniids, all solitary
parasitoids of cockroach oothecae, are as large and conspicuous as the Ampulex sp. (Townes
1949> The parasitic relationship
of an Evania species with
cockroaches was reported by Arnold as early as 1826 (Roth & Willis
1960). Evaniids also called ensign
flies because of their flag-shaped abdomens, are often found at windows in cockroach
infested homes, and have been known to arouse more complaints than the
cockroaches themselves (Edmunds 1953, LeBeck 1985).
Chalcidoids which parasitize cockroach oothecae are all gregarious and
relatively small (1-2 mm) compared to the ampulicids and evaniids. Female parasitoids search for oothecae in
secluded cockroach habitats. The
minute males attracted to windows in cockroach infested homes are not easily
detected. Host associations were
recorded in 1838 by Sells (Westwood 1839) who reported the emergence of 96
individuals of a Pteromalus
sp. from a single ootheca. Westwood
(1839) discovered Eulophus
sp parasitizing a Periplaneta
americana L. ootheca on a
ship. In 1852 Ratzeburg described a
eulophid Entedon
hagenowii (= Tetrastichus hagenowii) from a Blatta orientalis (L.) ootheca.
Possibly the same eulophid species was described by Westwood
(1939). This parasitoid was later
erroneously reported as a hyperparasitoid of Evania appendigaster L. by Marlatt (1915). Schmidt (1937) determined that T. hagenowii Ratzeburg was a primary parasitoid of several
domestic cockroaches (Roth & Willis 1960, LeBeck 1985).
Observations on the oviposition and parasitic behavior of cockroach
parasitoids continued during the early 1900's, when researchers began to
evaluate their potential as biological control agents and reports on
parasitoid biologies, natural and experimental parasitization rates, and host
specificities appeared during the 1940's and 1950's (LeBeck 1985). Roth & Willis (1060) reviewed
cockroach predators and parasitoids, stimulating further biological control
work. Detailed studies of
experimental and naturally occurring parasitoid populations and their effects
were made on several species, but the importance of cockroaches as urban
pests continues. Cockroaches may
damage stored and household goods and could act as disease vectors, besides
being unappealing to humans. Parasitoids
Comperia merceti
(Compere) is a widespread, host specific and gregarious parasitoid of the
brownbanded cockroach, Supella
longipalpa (Fab.). The brownbanded roach is found throughout
the United States in warm habitats ranging from homes to animal rearing rooms
in research facilities. It has also
become an increasingly important domestic pest. Experiments indicate that C.
merceti is a potentially
effective biological control agent for this roach. Basic biological studies include descriptions of developmental
stages, sex ratio, mating behavior, longevity and fecundity (Lawson 1954,
Gordh 1973). However, the problems of
parasitoid temperature sensitivity and developmental thresholds are not
addressed. In addition, contradictory
statements regarding host age preference exist (Lawson 1954, Gordh
1973). LeBeck (1985) investigated C. merceti, determining the optimum developmental temperature
and tolerance, and the oothecal age it prefers for oviposition in an effort
to improve mass culture techniques and control strategies. The internal morphology of the female
reproductive system was described, as only a few species of the Encyrtidae
have been examined internally (Bugnion 1891, Ishii 1932). LeBeck (1985) discovered a yeast-like
microorganism within the C. merceti body and its
transmission via the reproductive system.
The yeast-like organism was found to be non pathogenic and
extracellularly symbiotic. It was
transmitted to offspring as a non budding infective form via poison injected
into the ootheca during oviposition.
Its growth within the parasitoid, anatomical locations and the physiological
tolerance of the parasitoid to large quantities of yeast, indicated it might
be beneficial. The yeast was
tentatively placed in the Cryptococcoideae.
Attempts to produce aposymbiotic individuals failed. Cockroach Natural Enemies Considered by Family Ampulicidae.--Ampulicids are all predators of cockroaches (Krombein
1979). Although prey relationships
have been recorded, little work has been done on their biology (LeBeck
1985). The stinging and predatory
behavior of the adult female was first observed by Ferchauld (1742). Evidently a behavioral change versus a
true paralysis results from a sting near the subesophageal ganglion of the
cockroach (Williams 1929, 1942; Piek et al. 1984). Piek et al. (1984) determined that Ampulex
compressa Fab. stings its
prey twice. The first sting in the
thorax area causes a short,a reversible paralysis, while the second sting
near the subesophageal ganglion results in submissive, lethargic behavior. After the female wasp has prepared a nest,
she returns to the cockroach and brings it back to the nest. Frequently the cockroache's antenna are
severed to allow feeding on the hemolymph.
The nest is closed after the wasp deposits an egg on the surface of
the cockroach. Various
ampulicids were described by Williams (1942) as "semi-domiciliary"
since they have been known to hunt in and around homes for Periplaneta spp. In 1917 Williams (1942) introduced Dolichurus stantoni Ashmead into the Philippines, and it subsequently
spread to several adjacent islands and by 1920 had reportedly suppressed some
cockroach populations (Phyllodromia (= Blattella)
species) (Williams 1944). Podium haematogastrum (= Penopodium haematogastrum L.), an ampulicid from Brazil, was released
in Honolulu in 1925 but failed to become established. In 1940 Ampulex compressa
was introduce to Hawaii from New Caledonia (Williams 1942). Approximately 200 mass reared mated
females were released in Honolulu and on the islands of Maui and Kauai. Pemberton (1953) believed A. compressa provided good control of cockroaches and noticed
population reductions at the University of Hawaii poultry farm. It has since been introduced to Guam
(1954) and the Cook Islands (1955) to control Periplaneta spp. but its establishment and efficiency has
not been evaluated (Dumbleton 1957).
This parasitoid remains established on Oahu, Maui and Kauai and can be
locally common in certain situations (LeBeck 1985). Although laboratory data show females can live up to 159 days
and capture up to 85 cockroaches (Williams 1942), these results do not
reflect the natural mortality factors encountered in the field. The biology of this species would make it
difficult to mass culture economically and its large size (ca. 2.5 cm) would
not be readily accepted by homeowners. Evaniidae.--All evaniids are solitary parasitoids of cockroach
oothecae. Townes (1949)
differentiated the evaniids from other Hymenoptera by the attachment of the
abdomen near the top of the propodeum and the long anal lobe at the base of
the hind wing. Host records show they
parasitize many important cockroaches except the German cockroach, Blattella germanica (L.) for which Roth & Willis (1960) listed
some erroneous rearings (LeBeck 1985).
Non domestic species such as the wood roaches, Parcoblatta sp., are also
attacked (Townes 1949, Edmunds 1953).
Evania appendigaster (L.) is usually
found wherever species of Periplaneta
and Blatta are found. This parasitoid is most abundant in the
subtropics and tropics, but it is also established and common in many
temperate metropolitan regions (Townes 1949). Because of its large size and urban habitats, Evania appendigaster has received most research attention (LeBeck
1985). MacLeay (Westwood 1943) first
determined that it developed within cockroach oothecae. A detailed description of oviposition by
Haber (1920) dispelled the thought that females used their cleaverlike
abdomen to open the ootheca at the seam to deposit eggs. Instead, the female assumes a parallel
position over the ootheca and after extensive drilling ( 1/2 hr) deposits one
egg (Haber 1920, Crosskey 1951, Cameron 1957). Cameron (1957) produced the first complete biology of the
parasitoid including searching behavior, oviposition and morphology of developmental
stages, and discussed biological control potential. Individuals provided with food and water survived 2-3
weeks. Field parasitization of P. americana oothecae averaged 25-29%. By comparison, Narasimham & Sankaran
(1979) reported up to 6.8% field parasitization by E. appendigaster
of all oothecae collected in buildings and huts at various locations in
India. An oothecal survey of Periplaneta and Blatta species in 17 Texas and
4 Louisiana cities during 1974-75, produced only four adults of this parasitoid
(Piper et al. 1978). Evania appendigaster
reportedly had a significant impact on cockroach populations, but was not
rated as desirable for biological control as T. hagenowii
(Cameron 1957). This is because E. appendigaster is solitary whereas T. hagenowii
is gregarious, although both parasitoids destroy all cockroach eggs within an
ootheca. Also, the total
developmental time for E. appendigaster is 50-60 days
while for T. hagenowii it is 24-30 days at
comparable temperatures; and any disturbance of the ootheca will kill the
evaniid, whereas T. hagenowii often completes
development successfully. Cameron
(1957) nevertheless admitted that female E.
appendigaster appeared to be
a better searcher. Another evaniid,
Prosevania punctata (Brulle) is quite
similar to E. appendigaster (Cros 1942,
Edmunds 1952, Cameron 1957), and has a preference for the oothecae of P. americana when compared to Blatta orientalis
or Parcoblatta pennsylvanica (DeGeer). LeBeck (1985) reported on P. punctata attacking B.
orientalis, ovipositing in
oothecae <1-week old and requiring 50-60 days to develop at ca. 25°C, which
are similar to findings of Cros (1942), Edmunds (1952) and Cameron
(1957).
Edmunds (1952) suggested that female parasitoids may discriminate
between parasitized and unparasitized oothecae in evaniids. Host records of other genera of evaniids
are available (LeBeck 1985), but biological information on most species is
limited to dissections of parasitized oothecae or observations of adult
emergence (Genieys 1924, Edmunds 1953, Roth & Willis 1960). The evaniids may play a significant role
in reducing cockroach populations, but research on their biological control
potential is wanting (LeBeck 1985). Pteromalidae.--Only one pteromalid known to parasitize a
cockroach ootheca is Systellogaster
ovivora Gahan. This species was described by Gahan (1917)
from a "Blatta"
ootheca in the United States, and Edmunds (1953) and Judd (1955) reared these
gregarious parasitoids from Parcoblatta
species in the North America. Edmunds
(1953) recorded up to 27 individual parasitoids per ootheca, and Judd (1955)
found 14 individuals with a 75% female sex ratio in one parasitized ootheca;
there were 2-3 emergence holes per ootheca. Wood cockroaches, Parcoblatta, are not considered
urban pests, so that S. ovivora would only be of
importance if it also successfully parasitized B. orientalis
(L.). Peck (1951) and Thompson (1950)
listed B. orientalis as a host for S. ovivora but only refer to Gahans' (1917) description (see
LeBeck 1985). Eupelmidae.--Roth & Willis (1960) identified six apparently different
eupelmid species as parasitoids of cockroach oothecae, including Anastatus blattidifurax Girault, and Eupelmus atriflagellum Girault, from
cockroach hosts in Australia, Eupelmus
sp. from a tree cockroach in Florida, Anastatus floridanus Roth & Willis, Anastatus tenuipes Bolivar &
Pieltain, and Solindenia
picticornis Cameron from
Allacta similis (Sauss>0 in Hawaii
(Roth & Willis 1960). In India,
Narasimham & Sankaran (1979) found an additional eupelmid parasitizing
oothecae of Neostylopyga
rhombifolia
(Stoll) and Periplaneta
sp. Bou…ek (1979) named it Anastatus
umae sp. nov., and
Narasimham & Sankaran (1982) evaluated its biological control potential
on field breeding cockroaches. LeBeck
(1985) notes that the biologies of A.
tenuipes and A. floridanus have also been studied. Anastatus tenuipes
Bolivar (= Anastatus
blattidarum Ferriere) seem host
specific for the oothecae of Supella
longipalpa (F.) (Flock 1941,
Roth & Willis 1960). This
parasitoid, of African origin, appears to have followed its host through the
West Indies into Florida and across the United States (Flock 1941). Flock's (1941) study of this parasitoid
included longevity, sex ratio, developmental time, and oviposition
behavior. Several females oviposit
into one ootheca, and yet the progeny sex ratio is ca. 6:1 females. Oviposition time ranged from 15-45 min.
and females were observed to host feed.
Only four parasitoids per ootheca can destroy all the cockroach eggs,
but Flock found the average number to be about 10 per ootheca. At 25°C the mean developmental time from egg to adult
was 32.6 days. Parasitoids survived
to two weeks when furnished with honey or water. Ferriere (1935) reported a sex ratio of 80% females from A. tenuipes and an average of 15 individuals per
ootheca. The parasitoid might be
useful in biological control because of its high female biased sex ratio,
gregarious nature and relatively short developmental time (Flock 1941). But Narasimham & Sankaran (1979) found
a very low field parasitization rate of 1% in S. longipalpa
oothecae in India. They found that Comperia merceti (Compere) apparently out competed A. tenuipes, even in areas where the latter had been
experimentally introduced.
Another cockroach, Eurycotis floridana
(Walker) is usually found in xeric hammock habitats in the southeastern
United States, but is occasionally an urban pest (Roth & Willis
1954a). Roth & Willis (1954a)
described a eupelmid oothecal parasitoid Anastatus
floridanus Roth & Willis
of E. floridana and studied its biology. This parasitoid is gregarious, preferring
the ootheca of E. floridana, but will also
oviposit and develop in P. americana and B. orientalis.
Oothecae still associated with the female cockroach, or deposited up
to 36 days are acceptable for oviposition.
One female can spend up to 5-hrs ovipositing in one ootheca, and will
also host feed. At 27°C
developmental time ranged from 34-46 days depending on parasitoid
density. One female oviposited an
average of 50 eggs per ootheca and the developing larvae usually consumed all
cockroach eggs. Roth & Willis
(1954a) dissected a maximum of 709 parasitoid larvae from one
superparasitized ootheca and concluded that larval cannibalism must occur
because brood size in such oothecae averaged 300. All individuals emerged from an average of 2 holes chewed in
the ootheca with a sex ratio of 80% females.
Provided with food and water A.
floridanus is short lived at
25°C, females living only four days and males surviving just one
day. A
eupelmid was reared from the oothecae of Neostylopyga
rhombifolia in India by
Narasimham & Sankaran (1979).
They reported parasitization rates of 27-84% from 164 oothecae. Oothecae of were accepted for oviposition,
but when offered a choice between N.
rhombifolia and Periplaneta sp., A. umae always chose the former. Narasimham & Sankaran (1982) continued their study of this
parasitoid because of its preference of N.
rhombifolia which is a
domestic pest in India, especially in thatched huts. There the roach deposits oothecae only on
the inner side of palm leaves which form the roof. Laboratory studies showed that A. umae preferred
to oviposit in low light conditions, possibly explaining the parasitoids
initial attraction to darkened hut interiors versus well lighted buildings
(LeBeck 1985). In an evaluation of A. umae on Periplaneta
sp. in the field, several sites were chosen at which both N. rhombifolia and A.
umae were absent. Post release oothecal surveys failed to
recover A. umae from the field sites, and
neighboring houses were also surveyed to no avail to determine if A. umae had dispersed in search of N. rhombifolia. Periplaneta
sp. oothecae recovered were parasitized by two Tetrastichus spp.
In order to test the effects of multiple parasitism between A. umae and these species, Narasimham & Sankaran (1982)
offered each species oothecae parasitized by the other. Results showed that in either case the Tetrastichus out competed A. umae, which might explain why no A. umae
were reared from the release site oothecae.
At these sites, the Tetrastichus
species were hyperparasitized by another Tetrastichus
parasitoid, and further studies revealed that the hyperparasitoid did not
attack A. umae. Encyrtidae.--The biology of only one encyrtid oothecal parasitoid of
cockroaches, Comperia merceti (Compere) has been
studied (Roth & Willis 1960, LeBeck 1985). Apart from the unreliable observations which suggest that C. merceti parasitizes Blattella
germanica (Roth & Willis
1960), all studies indicate that C.
merceti is host specific for
the oothecae of Supella longipalpa (LeBeck 1985). Zimmerman (1948) gave an early indication
that C. merceti was efficient on S. longipalpa. He noted that after the accidental
introduction of Comperia
falsicornis (= C. merceti) in Hawaii, S.
longipalpa was
"practically wiped-out" in some areas, and oothecal surveys showed
parasitization reaching 100%. Lawson
(1954) produced the first thorough biology of C. merceti,
including a detailed description of developmental stages from egg to adult,
mating behavior, longevity and oviposition,.
He also noted that C.
merceti was gregarious,
endoparasitic (5-25 individuals per ootheca) and usually consumed the entire
contents of the egg case. Adults
emerge via a single exit host and mating takes place immediately. Lawson (1954) offered a possible
preoviposition period and described oviposition in which the female deposits
an average of 10 eggs per ootheca, each egg visible externally by a stalked
pedicel. The developmental period
(egg-adult) at room temperatures was 30-41 days. Adults survived 3-5 days, but the addition of food did not
extend longevity (Lawson 1954).
Gordh (1973) confirmed that C.
merceti was host specific
for S. longipalpa, but contrary to Lawson showed that with honey
and water adult female longevity was significantly increased by the constant
addition of host oothecae. Gordh
(1973) explained mating behavior in terms of negative and positive
phototaxis, and divided parasitization behavior into stages of wandering,
searching, exploring, oviposition and repulsion. Oviposition in itself could last 35-50 min., but females could
not detect previously parasitized oothecae.
It was thought that host attractiveness was due to the cementing
substance that fixes the ootheca to the substrate. Sex ratio was ca. 66% female.
The first mass culture and experimental release of C. merceti against brownbanded cockroaches was attempted by
Slater et al. (1980) on the campus of the University of California,
Berkeley. During Jan 1978-Dec 1979,
over 20,000 parasitoids were released in offices, classrooms, animal rearing
rooms and laboratories. Results
showed that C. merceti successfully became
established. It was suggested that
periodic augmentation of the parasitoid might increase parasitization rates
which only reached 19% in one location.
Similar natural parasitization rates (19.5%) for C. merceti
were reported by Narasimham & Sankaran 91979) in India. The need for inundative releases of C. merceti, especially when S. longipalpa
population were low, was confirmed by Coler et al. (1984). They gave the first quantitative data of
the suppression of S. longipalpa populations by
analyzing the progressive change in the cockroach age structure over
time. Furthermore, they determined
that the parasitoid was more efficient at higher cockroach densities and
reached parasitization rates of 95%.
Van Driesche & Hulbert (1984) gave quantitative data suggesting
that the cement substance binding the S.
longipalpa ootheca to the
substrate acted as a kairomone which contributes to host acceptance. The optimal density range for resource
utilization by C. merceti was analyzed (Van
Driesche & Hulbert 1984). It was
concluded that the parasitoid can discriminate between parasitized and
unparasitized oothecae, and subsequently oviposits at reduced levels in the
former. Eulophidae.--The eulophid genera Tetrastichus
and Syntomosphyrum contain
several gregarious parasitoids of cockroach oothecae, and two known
hyperparasitoids (Roth & Willis 1960).
Both domestic and nonurban cockroach pest species are attacked (LeBeck
1985). The most widespread oothecal
parasitoid in this group, Tetrastichus
hagenowii (Ratzeburg), has
the broadest host range, including the most cosmopolitan cockroach pests
(LeBeck 1985). Early descriptions and
host records of this parasitoid (Ratzeburg 1852) reported large numbers of
parasitoids emerging from one ootheca.
Marlatt (1915) believed Entedon
hagenowii (Ratzeburg) (= T. hagenowii) was a hyperparasitoid of Evania appendigaster,
but Schmidt (1937) proved it to be a primary parasitoid. Biological studies were performed by
several investigators (Maki 1937, Usman 1949, Roth & Willis 1954b,
Cameron 1955). Other studies report
natural and experimental percent parasitism and host suppression (Amonkar et
al. 1974, Fleet & Frankie 1975, Kanayama et al. 1974, Piper et al. 1978,
Narasimham 1984). Tetrastichus hagenowii
has a broad host range, but it laboratory tests showed that prefers to the
oothecae of Periplaneta
spp., especially P. americana (Roth & Willis
1954b, Narasimham & Sankaran 1979, Narasimham 1984). In field studies comparing parasitism of P. americana and Periplaneta
fuliginosa (Serville) there
seems to be no preference, however (Fleet & Frankie 1975). Blattella
germanica has been listed as
a host of T. hagenowii, but Roth &
Willis (1960) considered such observations in error. LeBeck (1985) stated that there is no
solid data for any oothecal parasitoid of B.
germanica, most likely
because females deposit oothecae just prior to its hatching. Oviposition by T. hagenowii
in S. longipalpa oothecae has been observed, but parasitism
failed (Roth & Willis 1954b, Narasimham & Sankaran 1979). Host searching of T. hagenowii
was studied by Narasimham (1984), showing that parasitoids first seek the
proper habitat. They are attracted to
relatively dry environments, became inactive at 19°C and
avoided high temperatures (>34°C).
Visual stimuli did not appear to function in host location, and
following trials that included oothecal extracts, Narasimham (1984) concluded
that the female was not attracted to the host by chemical stimuli
either. There were random movements
of the female observed until she was within 2-3 mm of an ootheca. Oothecae up to 30 days old were acceptable
for oviposition, but those close to hatching were rejected (Roth & Willis
1954b). Tests in houses found no
differences in parasitization rates between concealed and exposed oothecae of
Periplaneta spp. (Fleet
& Frankie 1975, Piper et al. 1978).
Host-feeding may accompany oviposition (Roth & Willis 1954b,
Narasimham 1984), but Edmunds (1955) did not observe it. Often a female parasitized only 1-2
oothecae during her lifetime (Narasimham 1984). An average of 4.8 oothecae were selected for oviposition by
each female, primarily during the first two days of adult life (Roth &
Willis 1954b). Eggs float freely in
the yolk and hatch within 24-hrs.
Cameron (1955), Edmunds (9155) and Narasimham (1984) described the
immature stages and developmental time from egg to adult at 20-28)C ranges
from 24-60 days (Maki 1937, Cameron 1955, Edmunds 1955, Narasimham 1984,
Wen-Qing 1985). Superparasitism
occurs commonly suggesting that T.
hagenowii cannot detect
previously parasitized hosts. The
number of parasitoids emerging per ootheca can be large (LeBeck 1985). Narasimham (1984) found that as the number
of parasitoids per ootheca increased, the percentage of male parasitoids
increased, adult size decreased and life span of the progeny decreased. Developmental time was less when brood size
was >70 individuals, compared to broods of 60 or less individuals (Fleet
& Frankie 1975). The sex ratio is
usually female biased (3:1), although Narasimham (1984) thought it varied
depending on host size (more females from larger oothecae) and species. All parasitoids emerge at once from 1-3
chewed holes (Roth & Willis 1954b), and mating follows (Cameron 1955,
Edmunds 1955, Wen-Qing 1985).
Longevity of females with or without food is variable (LeBeck 1985).
Field parasitization is variable and reflects differences in the host
species and population size sampled (LeBeck 1985). Narasimham & Sankaran (1979) in a survey in India found
that 16% of all P. americana oothecae were
parasitized by T. hagenowii, but that only 1% of
each P. brunnea and P. australaisae
showed parasitism. Following
inundative releases of T. hagenowii, Roth & Willis
(1954b) recorded 83% parasitization of P.
americana in experimental
rooms. Piper et al. (1978) in a
survey of cities in the southern United States reported 26% of all collected
oothecae were parasitized, with 99.4% by T.
hagenowii. Tetrastichus asthenogmus (Waterson) is another eulophid that was
considered synonymous with T.
hagenowii by Roth &
Willis (1960) until Bou…ek (1979) distinguished it as a separate
species. Narasimham & Sankaran
(1979) then found T. asthenogmus to be
reproductively isolated from T.
hagenowii, and 2.5X more
abundant than T. hagenowii in oothecae collected
in India. Only Periplaneta sp. were attacked with a slight preference for
P. brunnea (11%) compared to P. australasiae
(9.5%) and P. americana (4.7%). In laboratory tests T. asthenogmus
chose P. brunnea in 14 out of 20
trials. Tetrastichus asthenogmus
is gregarious and biologically very similar to T. hagenowii
(Narasimham 1984). Females require no
preovipositional period and accept oothecae up to 30 days old. Narasimham (1984) found that developmental
time at 26°C was 43 days, and an average of 69.5
parasitoids emerged per ootheca. It
was concluded that T. asthenogmus was a poor searcher
from field experiments which showed that % parasitization increased with an
increase in host density. However,
the higher incidence of T. asthenogmus in the field when
compared to T. hagenowii, and its preference
for P. brunnea oothecae (common around Bangalore, India)
encourages its use as a biological control agent.
There is only limited information on other primary eulophid
parasitoids of cockroach oothecae (Roth & Willis 1960). Syntomosphyrum blattae
Burks, collected in the eastern United States (Burks 1979) develops in Parcoblatta sp. oothecae. Edmunds (1952, 1953) reared averages of 92
and 74 wasps per oothecae from two collections, and noted that 2-3 emergence
holes were common. Wen-Qing (1985)
reported a Tetrastichoides
sp. from P. fuliginosa in China, but did
not give any biological information. Hyperparasitoids.--There have been only two hyperparasitoids,
both eulophids, reared from parasitized cockroach oothecae (LeBeck
1985). Syntomosphyrum ishnopterae (Girault)
parasitizes Zeuxevania
splendidula Costa in
oothecae of Loboptera
decipiens (Germar) in
France (Parker & Thompson 1928).
Mating behavior has been described as well as oviposition and larval
development. Eggs hatched within 3
days and S. ioshnopterae larvae on the
evaniid host (Parker & Thompson 1928).
There were 30 and 50 individuals reared from two oothecae,
respectively, with a female biased sex ratio of 5:1.
Narasimham & Sankaran (1979) found a Tetrastichus sp. A. (near T. miser
(Nees)) in India. It was regarded as
an important hyperparasitoid because its hosts, T. hagenowii,
T. asthenogmus and C.
merceti were all considered
good biological control agents (LeBeck 1985). Twelve percent of all Periplaneta
sp. that were parasitized by T.
hagenowii or T. asthenogmus were hyperparasitized. Tetrastichus
sp. A was also reared from one ootheca that was parasitized by C. merceti, but oothecae parasitized by A. umae, A. tenuipes or a combination of these Anastatus spp. with C.
merceti, were not acceptable
to the hyperparasitoid. Further
studies by Narasimham (1984) showed that Tetrastichus
sp. A located its parasitoid host by larval movement and thus usually
oviposited when 3rd instar larvae were present. Oviposition averaged 3-75 min. and if the ovipositor of the
hyperparasitoid located only one cockroach embryo, it would feed on the
cockroach and leave. Upon
successfully contacting a host larva, the hyperparasitoid would feed and
reinsert the ovipositor to lay an egg.
Narasimham (1984) described mating behavior and determined that
unmated females produced only male progeny.
Oothecae yielded an average of 33 adults, and hyperparasitoids
oviposited into more oothecae per female than it parasitoid host. Provided with honey, the female
hyperparasitoids increased their life span from 5 to 12 days. The addition of oothecae (either
parasitized or unparasitized) allowed host feeding to supplement the diet and
further extended the female life span to 16 days. Although female C.
merceti did not host feed,
Gordh (1973) showed that a constant supply of fresh oothecae increased
longevity. In evaluating the
efficiency of this hyperparasitoid, Narasimham (1984) showed that its longer
life span and tendency to visit more potential hosts could have an adverse
impact on the primary parasitoid population.
However, field studies showed that the hyperparasitoid population
density was log because females wasted time searching as parasitism was only
detected in oothecae after drilling.
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