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Blatella germanica (L.), Blatta orientalis L., Periplaneta americana (L.), Periplaneta

fuliginosa (Serville) & Supella longipalpa (F.), --Orthoptera, Blattidae & Blattellidae





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Cockroaches rank among the most important pests in city and town environments (Ebeling 1975). Most species are of tropical or subtropical origins and thus by being invaded pests in temperate climates would seem to be ideal candidates for classical biological control (Dahlsten & Hall 1999). Cockroaches are known to contaminate food, leave unpleasant odors in residences and are thought to transmit disease (e.g., hepatitis). Allergic reactions can occur to cockroaches, probably from contact with cockroach body secretions or feces (Ebeling 1975). Principal species of importance in North America include the German cockroach, Blatella germanica (L.), the American cockroach, Periplaneta americana (L.), the brownbanded cockroach, Supella longipalpa (F.), the Oriental cockroach, Blatta orientalis L. and the smokybrown cockroach, Periplaneta fuliginosa (Serville). Common names affixed to the species seemingly to denote origin are undoubtedly misleading since both the German and American cockroaches most probably originated in the Ethiopian Realm.


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.




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.




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. 25C, 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. Bouek (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 25C 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 27C 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 25C, 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 19C and avoided high temperatures (>34C). 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 Bouek (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 26C 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. This hyperparasitoid is only known from India, and Piper et al. (1978) found no hyperparasitoids during a study of Periplaneta and Blatta oothecae from 17 Texas and 4 Louisiana towns.



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