Stable Fly Pupae Research Articles

Burial and Compaction of Sandy Soils to Prevent Emergence of Adult Stable Fly (Diptera: Muscidae) at the Soil Surface.

Stable fly (Stomoxys calcitrans L.) remain a significant pest affecting livestock and rural communities on the Swan Coastal Plain around Perth, Western Australia. Vegetable crop residues remaining after harvest enable stable fly development. Left untreated they can produce from several hundred to >1,000 stable fly/m2 of post-harvest residues. We studied the effect of burial and compaction of sandy soils on adult emergence of stable fly and house fly (Musca domestica L.) (Diptera: Muscidae). Adults of both fly species can move up through 50 cm of loose, dry sand, however at depths greater than 60 cm, emergence rapidly declines with <5% of adults surviving under 100 cm of soil. Burial of stable fly larvae and pupae under 15 cm of soil followed by compaction using a static weight dramatically reduced adult emergence. Moist soil compacted at ≥3 t/m2 completely prevented stable fly emergence whereas house fly emergence was not affected. One t/m2 of compaction resulted in <5% emergence of stable fly buried as pupae. Soil that was easily compactible (i.e., high silt, fine sand and clay content) reduced stable fly emergence more than soil with more coarse sand and low clay content. This study demonstrates the potential for a novel and chemical-free option for controlling stable fly development from vegetable crop post-harvest residue. Field trials are needed to confirm that burial and compaction of vegetable post-harvest residues using agricultural machinery can dramatically reduce the subsequent emergence of adult stable fly on a large scale.

The Ability of Selected Pupal Parasitoids (Hymenoptera: Pteromalidae) to Locate Stable Fly Hosts in a Soiled Equine Bedding Substrate: Table 1.

The ability of Spalangia cameroni Perkins, Spalangia endius Walker, and Muscidifurax raptorellus Kogan and Legner to locate and attack stable fly hosts was evaluated under laboratory conditions. Postfeeding third-instar stable fly larvae were released and allowed to pupate in two arena types: large 4.8 liter chambers containing a field-collected, soiled equine bedding substrate; or 120-ml plastic cups containing wood chips. At the time of fly pupariation, parasitoids were released and permitted 72 h to locate and attack hosts. On average, parasitism rates of freely accessible stable fly pupae in cups were not significantly different between parasitoid species. However, parasitism rates in chambers containing either Spalangia spp. were ≈50-fold more than M. raptorellus. Additional intraspecies analysis revealed that parasitism rates both by S. cameroni and S. endius were not significantly different when pupae were freely accessible or within bedding, whereas M. raptorellus attacked significantly more pupae in cups than in the larger chambers where hosts were distributed within bedding. These results suggest that Spalangia spp. are more suited to successfully locate and attack hosts in habitats created by equine husbandry in Florida. Therefore, commercially available parasitoid mixtures containing Muscidifurax spp. may be ineffective if used as a control measure at Florida equine facilities.

Distribution and abundance of natural parasitoid (Hymenoptera: Pteromalidae) populations of house flies and stable flies (Diptera: Muscidae) at the University of Florida Dairy Research Unit

From September 2001 through September 2002, house fly and stable fly pupae were collected weekly from three fly habitats at the University of Florida Research dairy in northcentral Florida and evaluated for parasitism. Varying parasitism percentages were observed throughout the study but they were not affected by temperature, precipitation or fly abundance. Of the 6,222 house fly pupae and 1,660 stable fly pupae that produced either a host fly or a parasitoid, 26.9% and 26.7% were parasitized, respectively. Ten parasitoid species were recovered, with the genus Spalangia accounting for 85.7% of the total; the most common parasitoids attacking house fly and stable fly pupae were Spalangia endius Walker (33.9% and 27.3%), S. cameroni Perkins (27.9% and 40.6%), and S. nigroaenea Curtis (21.0% and 24.8%), respectively. Other parasitoids included one specimen of S. erythromera Förster and four specimens of Phygadeuon fumator Gravenhörst (Ichneumonidae). The percentage parasitism of pupae collected from bunker silos was higher than that of pupae from calf pens and open pastures. Spalangia cameroni was consistently recovered through the entire year. Spalangia nigroaenea was predominant in July, August, and September. Spalangia endius was most active from October to May with a peak of relative abundance in January.

Retention ofEscherichia coliby House Fly and Stable Fly (Diptera: Muscidae) During Pupal Metamorphosis and Eclosion

Populations of Escherichia coli obtained by feeding larval house flies, Musca domestica L. and stable flies, Stomoxys calcitrans (L.), persisted through the pupal stage. The abundance of E. coli in house fly pupae increased initially then declined before adult emergence. Abundance of E. coli in stable fly pupae increased through pupal development and remained high. Infected stable fly pupal cases typically contained more E. coli than house fly pupal cases. A greater proportion of emerging adult house flies were infected with E. coli compared with stable flies; however, the abundance of E. coli on infected flies was similar between species. Adult flies contained 0.04-0.19% of the E. coli in the pupal cases. The proportion of infected house fly adults and the amount of E. coli on the infected flies were related to the levels of E. coli in the pupal cases; however, these relationships did not occur with the stable fly. Results suggest that retention of E. coli from larval to adult house flies could play a role in the transmission and spread of E. coli, whereas stable fly adults probably play a minor role in E. coli spread. However, pupae of both species have potential to act as reservoirs for E. coli.

Host Mortality and Progeny Production by Solitary and Gregarious Parasitoids (Hymenoptera: Pteromalidae) Attacking &lt;I&gt;Musca domestica&lt;/I&gt; and &lt;I&gt;Stomoxys calcitrans&lt;/I&gt; (Diptera: Muscidae) at Varying Host Densities

Relationships between host density and mortality of house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.), caused by Muscidifurax raptor Girault & Sanders, Muscidifurax zaraptor Kogan & Legner, Muscidifurax raptorellus Kogan & Legner, and Trichomalopsis sarcophagae Gahan were determined. Host mortality varied with host density and was highest when pupae were exposed to M. zaraptor followed by M. raptor, M. raptorellus, and T. sarcophagae. The relationship between host density and mortality was unaffected by host species for M. raptor and M. zaraptor; however, M. raptorellus killed a higher percentage of stable fly pupae and T. sarcophagae killed a higher percentage of house fly pupae. Residual mortality was higher on stable fly pupae than house fly pupae for M. zaraptor and M. raptorellus. The percentage of pupae with parasitoid emergence was reduced on stable fly pupae only for M. zaraptorand T. sarcophagae compared with house fly pupae. The gregarious species M. raptorellus and T. sarcophagae superparasitized pupae at low host densities and produced high numbers of progeny per female even at low host densities. Progeny production by T. sarcophagae was low on stable fly pupae compared with house fly pupae. The proportion female showed either no change or a small increase as host density increased for Muscidifurax species; however, T. sarcophagae had a greatly reduced proportion female at low host densities on house fly pupae. The number of female progeny per female parasitoid increased with host density for all parasitoid species except for T. sarcophagae parasitizing stable fly pupae. The reduced sex ratio of T. sarcophagae and low host mortality at low host densities suggested this species offers no advantage in terms of rearing efficiency, whereas the Muscidifurax species would be more efficient for rearing and release.

Activity of pupal parasitoids of the stable fly Stomoxys calcitrans and prevalence of entomopathogenic fungi in the stable fly and the house fly Musca domestica in Denmark

A survey was conducted on confined dairy cattle farms and a pig farm from May–October in 1999 to determine the activity and relative abundance of pupal parasitoids and the prevalence of entomopathogenic fungi in populations of the haematophagous stable fly, Stomoxys calcitrans (Diptera: Muscidae), in Denmark. Four species of pteromalids were found with Spalangia cameroni as the predominant. The other parasitoids were S. nigripes, S. nigra and Phygadeuon fumator (Ichneumonidae). Peak activity of the parasitoids was observed to be late in the summer and the beginning of autumn (August–September) when approximately 10% of the collected stable fly pupae were parasitised. Adult stable flies were infected with four species of entomopathogenic fungi: Entomophthora muscae, E. schizophorae, Beauveria bassiana and Verticillium lecanii. All fungi occurred in low percentages (max. 4%) and remained at this level throughout the sampling period. Likewise, adult house flies were infected with B. bassiana and V. lecanii,but Metarhizium anisopliae, Paecilomyces fumosoroseus and V. fusisporum were also recorded. The overall hyphomycete prevalence in house flies was 0.3%, and single species rarely exceeded 0.1%. The prevalence remained low in spite of increasing house fly numbers in August–September.

Hymenopteran Pupal Parasitoids Recovered from House Fly and Stable Fly (Diptera: Muscidae) Pupae Collected on Livestock Facilities in Southern and Eastern Hungary

This field survey, the second noting the occurrence and diversity of filth fly pupal parasitoid fauna in Hungary, was performed on beef and dairy feedlots and swine facilities in the southern and eastern parts of the country. The filth flies Musca domestica L. and Stomoxys calcitrans (L.) were the two most commonly parasitized hosts. The three species of Spalangia recovered, in decreasing order of abundance, were S. cameroni Perkins, S. nigroaenea Curtis, and S. endius Walker. Pachycrepoideus vindemiae Rondani, Trichomalopsis sp., two apparently undetermined Diapriidae spp. and one apparently undetermined Brachycera sp. are believed to be new country records.

SURVEY AND RELEASE OF PARASITOIDS (HYMENOPTERA) ATTACKING HOUSE AND STABLE FLIES (DIPTERA: MUSCIDAE) IN DAIRY OPERATIONS

AbstractIn 1995, Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae), a commercially available pupal parasitoid of the house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), was purchased to examine the status of wasps being sold to Manitoba producers. Percentage of pupae parasitized, numbers of parasitoids per pupa, total parasitoids, and parasitoid sex ratio were determined for each shipment of parasitoids received. To determine the extent to which these wasps could successfully parasitize house flies and stable flies, parasitoids were released weekly in four Manitoba dairy barns and levels of parasitism estimated. In 10 622 freeze-killed sentinel house fly pupae, 2.2% were parasitized throughout the season by N. vitripennis, and 5.8% were parasitized by eight other species of parasitoids. Of 11 897 naturally occurring house fly and stable fly pupae, 0.6% were parasitized by N. vitripennis, and 3.4% by eight other species of parasitoids. In four barns where there were no releases of N. vitripennis, 1.1% of 11 779 sentinel pupae were parasitized by four species of parasitoids and 3.8% of 8384 naturally occurring house fly and stable fly pupae were parasitized by nine species. The release of an estimated 3 648 093 N. vitripennis did not result in substantial parasitism in either sentinel pupae or naturally occurring pupae. In 1996, live sentinel house fly pupae (n = 50 842) and house fly and stable fly pupae occurring naturally (n = 4691) were collected in two of the nonrelease barns from the 1995 study to examine the activity of endemic parasitoids. Of the sentinel and naturally occurring pupae sampled, 4.0% and 9.4% were parasitized, respectively. Phygadeuon fumator Gravenhörst (Hymenoptera: Ichneumonidae) was the most abundant parasitoid, accounting for 97.4% and 79.9% of parasitoids collected from sentinel pupae and naturally occurring pupae, respectively. Other parasitoids included Urolepis rufipes (Ashmead), Muscidifurax raptor Girault and Sanders, Muscidifurax zaraptor Kogan and Legner, Spalangia subpunctata Först, Spalangia cameroni Perkins, Spalangia nigra Latreille, and a species of Trichomalopsis Crawford (Hymenoptera: Pteromalidae).

Releases of Spalangia nigroaenea andMuscidifurax zaraptor (Hymenoptera: Pteromalidae) Increase Rates of Parasitism and Total Mortality of Stable Fly and House Fly (Diptera: Muscidae) Pupae in Illinois Cattle Feedlots

Weekly releases of Spalangia nigroaenea Curtis and Muscidifurax zaraptor Kogan & Legner from May through August of 1991-1993 at small, owner-operated cattle feedlots in Illinois provided weekly emergence of 100-300 parasitoids of each species per feedlot animal. In assessments based on fly and parasitoid emergence from > 47,000 stable fly and house fly puparia collected during the 3-yr period, total stable fly mortality was greater in lots where releases were made (60.7%) than in paired, untreated control lots (51.7%) (P = 0.04; paired t-test); parasitism of stable fly pupae by S. nigroaenea averaged 11.6% where releases were made and 6.4% in paired control lots (P = 0.0016). In lots where releases were made, total mortality of house fly pupae was greater (68.7 versus 56.1%; P = 0.0001); unexplained mortality was greater (55.5 versus 46.1%; P = 0.0018); and parasitism by Muscidifurax spp. was greater (2.4 versus 1.4%; P = 0.07) than in paired control lots. Parasitism, unexplained mortality, and total mortality of both fly species varied significantly from 1991 to 1992 in lots that received the same treatment each year, presumably due primarily to weather. Over the 3-yr period, releasing these species, particularly S. nigroaenea, significantly reduced production of stable fly and house fly adults in cattle feedlots. The potential value of such reductions is likely to vary as a result of feedlot conditions and weather.

Relationships Between Temperature and Life History Parameters of Trichomalopsis sarcophagae (Hymenoptera: Pteromalidae)

The effect of temperature on the life history of the pteromalid parasitoid Trichomalopsis sarcophagae Gahan was determined to develop relationships that could be used for construction of simulation models of biological control. Immature developmental rates were not influenced by parasitoid sex or host species, and increased in a linear fashion with temperatures in the range of 15 to 30°C. Development was limited at 33°C. Immature development required 197 degree-days above 12.4°C. Immature survival was lowest at 15 and 33°C, and highest in the range of 22 to 26°C. Host species did not influence the relationship between temperature and immature survival, although fewer progeny were produced in pupae of the stable fly, Stomoxys calcitrans (L.), compared with the house fly, Musca domestica (L.). Sex ratio of emerging parasitoids was 79% female at 15°C, and 62–69% female at 20–30°C. Stable fly pupae yielded 64% females compared with 73% females from house fly pupae. House fly pupae yielded 8.2 progeny per pupa compared with 4.6 progeny per stable fly pupa. Median female longevity declined from 15–18 d at 15°C to 4–5 d at 33°C. Time to 50% oviposition ranged from 8–11 d at 15°C to <2 d at 33°C. Lifetime progeny production was lowest at 15 and 33°C, and >70 progeny per female at 25°C. The net reproductive rate was <1 female per female at 15 and 33°C and >38 female per female at 25°C. Mean generation time decreased from 89 d at 15°C to <12 d at 33°C. The intrinsic rate of increase was ≤0 female per female per day at 15 and 33°C, but >0.22 female per female per day at 25°C. T. sarcophagae appears better adapted to cooler temperatures than many other pteromalids, and may prove to be a useful biological control agent for filth flies in northern areas.

Release of a Gregarious Muscidifurax Species (Hymenoptera: Pteromalidae) for the Control of Filth Flies Associated with Confined Beef Cattle

Abstract A recently colonized gregarious species of Muscidifurax near raptorellus (Kogan and Legner) from eastern Nebraska was evaluated in the field for its potential as a biological control agent for the house fly (Micsca domestica L.) and stable fly (Stomoxys calcitrans (L.)). Muscidifurax sp. was released at three beef cattle feedlot pens, three times at 3-week intervals at 50,000, 100,000, or 200,000 parasitized hosts per treatment. Mean host mortality in sentinel house fly pupae reached 94% 2 weeks after the first release, but parasitism decreased to 72% after 3 weeks. Similar trends were observed with the second and third releases. Also, large numbers of parasite progeny were recovered from sentinel cohorts, suggesting that many of the released parasites found the sentinel pupae. Parasitism by Muscidifurax sp. was substantially lower, 27.4 and 12.2%, respectively, in naturally occurring house fly and stable fly pupae than that observed in sentinel hosts. Little correlation was evident between mean host mortality and a given parasite release rate. This Muscidifurax sp. has a high reproductive capacity, is easily reared, and appears to be one of the more effective species commercially available for fly control on midwestern beef and dairy cattle confinements.

Hymenopteran Pupal Parasites Recovered from House Fly and Stable Fly (Diptera: Muscidae) Pupae Collected on Livestock and Poultry Facilities in Northern and Central Hungary

The first field survey, noting the occurrence and diversity of filth fly pupal parasite fauna in Hungary, was done on beef and dairy feedlots, and swine and poultry farms in the northern and central parts of the country. Musca domestica L. and Stomoxys calcitrans (L.) were the two major filth fly hosts. Four species of Spalangia recovered, in decreasing order of abundance, were S. cameroni Perkins, S. endius Walker, S. nigroaenea Curtis, and S. nigra Latrielle. S. endius, Muscidifurax raptor Girault & Sanders, two apparently undescribed Trichopria spp. and one apparently undescribed Coptera sp. are believed to be new country records.

Utilization of Freeze-killed House Fly and Stable Fly (Diptera: Muscidae) Pupae by Three Pteromalid Wasps

Utilization of freeze-killed house fly, Musca domestica L., and stable fly, Stomoxys calcitrans L., pupae for development by the pteromalid parasitoids, Muscidifurax zaraptor Kogan and Legner, Pachycrepoideus vindemiae (Rondani) and Spalangia nigroaenea Curtis was investigated. All three species of parasitoids used both fly species as hosts. Parasitoid emergence from house fly and stable fly puparia was not significantly different for M. zaraptor and P. vindemiae. However, emergence of S. nigroaenea was significantly higher from house fly puparia than from stable fly puparia. When given a choice, all three pteromalid species preferred ovipositing on house fly pupae, as indicated by parasitoid emergence. Parasitoid emergence from house fly puparia comprised ca. 75, 58 and 90% of the total combined emergence from house fly and stable fly puparia for M. zaraptor, P. vindemiae and S. nigroaenea, respectively. For M. zaraptor, the proportion of female progeny from house fly puparia (ca. 60%) was significantly higher than that from stable fly puparia (ca. 47%). The proportion of females from house fly and stable fly puparia for P. vindemiae and S. nigroaenea was not significantly different.

Comparison of sentinel and naturally occurring fly pupae to measure field parasitism by pteromalid parasitoids (Hymenoptera)

In a series of studies over a 4-year period, the effectiveness of releases of pteromalid wasps for the control of house flies, Musca domestica L., and stable flies, Stomoxys calcitrans (L.), on beef cattle confinements was evaluated using sentinel house fly pupae (artificially reared and placed in the environment) and naturally occurring house fly and stable fly pupae. The two methods were compared using percentage parasitoid emergence and species composition. At confinements where no parasitoid releases occurred, parasitoid emergence was significantly higher from naturally occurring hosts. Muscidifurax zaraptor Kogan and Legner comprised 97 and 76% of the parasitoids recovered from sentinel and naturally occurring hosts, respectively. Spalangia spp. made up 16% of the parasitoids from naturally occurring hosts. Few Spalangia spp. were recovered from sentinel hosts. Similar results were obtained from locations where M. zaraptor was released except that M. zaraptor comprised a greater proportion of the parasitoids recovered by both methods. At locations where Spalangia cameroni Perkins was released, 76% of the parasitoids recovered from sentinel hosts were M. zaraptor, and 21% were S. cameroni, compared with 62% M. zaraptor and 34% S. cameroni from naturally occurring hosts. At locations where Pachycrepoideus vindemiae (Rondani) was released, this species was recovered significantly more often from sentinel hosts. Naturally occurring pupal method appears to be more reliable and sensitive to the entire parasitoid species complex. However, because of the difficulty in obtaining adequate samples, it is recommended that both methods be employed.

Relative Abundance of Stable Fly and House Fly (Diptera: Muscidae) Pupal Parasites (Hymenoptera: Pteromalidae; Coleoptera: Staphylinidae) on Confinement Dairies in California

Four dairies in southern California were sampled weekly from April 1987 through June 1988 to determine the distribution and relative abundance of stable fly, Stomoxys calcitrans (L.), and house fly, Musca domestica L., pupal parasites. Seven parasite species represented ≍90% of the parasites recovered from stable fly and house fly pupae, and included Spalangia endius Walker, Spalangia cameroni Perkins, Spalangia nigroaenea Curtis, Muscidifurax raptor Girault and Sanders, Muscidifurax zaraptor Kogan and Legner, Urolepis rufipes (Ashmead), and Aleochara spp. U. rufipes had not been previously recorded to parasitize these hosts in California. Most of the U. rufipes recoveries were between April and June. The relative abundance of parasites recovered from stable flies and house flies on four southern California dairies varied slightly for some species, but the overall rate of parasitism only ranged from 13.4 to 19.9%. A limited number of stable fly and house fly pupal collections from dairies in central California revealed a much lower proportion of S. cameroni and a higher proportion of S. endius , when compared with southern California dairies. The majority of stable fly and house fly pupae sampled at four southern California dairies were associated with pure manure substrates. There was no significant difference between the relative abundance of parasites recovered from stable fly pupae sampled from manure, manure plus hay, or wet-hay substrates. Significantly fewer S. nigroaenea and significantly more M. zaraptor were recovered from house fly pupae developing in brewer's grain when compared with manure, manure plus hay, and wet-hay substrates. In pupal samples which contained both stable flies and house flies, S. cameroni was recovered significantly more often from stable fly pupae. In general, there were no significant differences between stable fly and house fly in parasitism by the seven parasite species.

Seasonal and Relative Abundance of Hymenopterous Parasitoids Attacking House Fly Pupae at Dairy Farms in Central New York

A survey of indigenous parasitoids attacking Musca domestica L. and Stomoxys calcitrans (L.) pupae was conducted for 2 yr at eight dairies by exposing weekly samples of laboratory-reared fly pupae (sentinel bags). Mean relative abundance of each species was 59% Muscidifurax raptor Girault and Sanders, 14% Urolepis rufipes (Ashmead), 11% Phygadeuon fumator Gravenhorst, 10% Spalangia cameroni Perkins, 3% Spalangia nigroaenea Curtis, and 2% Trichomalopsis dubius (Ashmead). Rare species included Pachycrepmdeus vindemmiae (Rondani), Nasonia vitripennis (Walker), Dibrachys cavus (Walker), Spalangia nigra Latreille, and Macroneura vesicularis (Retzius). Total parasitism was phenologically synchronized with the house fly population occurring between 17 May and 27 October, but it peaked 1–2 mo after the fly population peaked. M. raptor, U. rufipes , and P. fumator were common in June. A decrease in parasitism by M. raptor and U. rufipes during late July may represent a gap between the first two generations. Paired samples of sentinel house fly and stable fly pupae indicated no difference in parasitism by M. raptor or by all species combined. However, U. rufipes parasitized more house fly pupae, and P. fumator parasitized more stable fly pupae.

A Field Study of Host Size Effects on Sex Ratio of the Parasitoid Wasp Spalangia cameroni

-I examined aspects of Charnov et al.'s (1981) host-size model for the parasitoid wasp Spalangia cameroni, using collections of fly pupae (hosts) from a poultry house. The model predicts that female parasitoid wasps should emerge from larger hosts than males. This prediction was supported for two collection dates in which only one host species, house flies, was parasitized by S. cameroni. The prediction was not supported either within host species or combining host species for the collection date in which both house flies and stable flies were parasitized. In fact, female S. cameroni emerged from smaller stable fly pupae than did males. The prediction of the host-size model also was not supported on a between-host species basis. Though stable fly pupae are significantly smaller than house fly pupae, the sex ratio (proportion of males) of S. cameroni emerging from stable flies was not significantly greater than from house flies. Contrary to expectations, field data showed no positive relationship between host size and female wasp size either within or between host species. Laboratory experiments indicated that female S. cameroni judge host size relative to the size of other hosts encountered, as predicted based on the significant temporal variation found in the host size distribution in the field.

Interspecific Differences in Host (Diptera: Muscidae) Size and Species Usage Among Parasitoid Wasps (Hymenoptera: Pteromalidae) in a Poultry House

Fly pupae, primarily house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), were collected from a poultry house in northern Indiana, and parasitoid wasps developing in them were allowed to emerge. Fly pupae density, relative species abundance, and size varied with collection date. Four species of parasitoid wasps were reared from the fly pupae: Spalangia endius Walker, S. cameroni Perkins, S. nigroaenea Curtis, and Muscidifurax raptor Girault & Sanders (Hymenoptera: Pteromalidae). There was some evidence of differential host species and size usage among the wasp species; but the differences were small, and there was considerable overlap. Percentage of parasitism was independent of host species for S. endius and S. cameroni , but M. raptor emerged from house fly pupae more frequently than expected by chance and from stable fly pupae less frequently than expected. S. endius emerged from larger hosts than did S. cameroni , despite S. endius being on average smaller than S. cameroni . This is the first study to examine differences of host size among these parasitoid wasps.

Effects of host age, host density and parent age on reproduction of the filth fly parasite Urolepis rufipes (Hymenoptera: Pteromalidae)

Urolepis rufipes Ashmead, a pteromalid wasp, was recently discovered parasitizing house fly and stable fly pupae in eastern Nebraska dairies. Studies have been conducted on the biology of this parasite to evaluate its potential as a biological control agent of stable flies (Stomoxys calcitrans (L.] and house flies (Musca domestica L.). House fly pupae were suitable as hosts for U.rufipes at all ages; however, significantly higher parasitism occurred on host pupae aged 96-120 h. Parasite-induced mortality (host mortality without progeny production) was higher than for other pteromalid parasites of filth flies under similar conditions. Parasitism increased with parasite--host ratio at 20 degrees C; however, the opposite was noted at 30 degrees C for parasite--host ratios ranging from 5:50 to 50:50. Fly eclosion decreased as parasite--host ratio increased at 20 degrees C, and no host eclosion occurred at the highest parasite--host ratios (20:50 and 50:50) at 30 degrees C. Females produced an average of 18.6 female and 7.6 male progeny. 88% of the progeny were produced during the first 6 days post parental eclosion. The short life span, low progeny emergence rate and high per cent host eclosion, in comparison with other parasite species, suggests that the Nebraska strain of U.rufipes may not an effective biological control agent of house flies.

Commercial and Naturally Occurring Fly Parasitoids (Hymenoptera: Pteromalidae) as Biological Control Agents of Stable Flies and House Flies (Diptera: Muscidae) on California Dairies

Filth fly parasites reared by commercial insectaries were released on two dairies (MO, DG) in southern California to determine their effect on populations of house flies, Musca domestica L., and stable flies, Stomoxys calcitrans (L.). Spalangia endius Walker, Muscidifurax raptorellus Kogan and Legner, and Muscidifurax zaraptor Kogan and Legner were released on the MO dairy from 1985 to 1987 in varying quantities. Parasitism by Muscidifurax zaraptor on the MO dairy was significantly higher (P less than 0.05) from the field-collected stable fly (4.4%) and house fly (12.5%) pupae, compared with a control dairy (0.1%, stable fly; 1.3%, house fly). Muscidifurax zaraptor, released from April through October during 1987 on the DG dairy (350,000 per month), was not recovered in a significantly higher proportion from either fly species relative to the corresponding control dairy. No specimens of Muscidifurax raptorellus were recovered from the MO dairy. Parasite treatments had no apparent effect on adult populations of either fly species or on overall parasitism rate of field-collected stable fly (16.8%, MO; 17.2%, DG) and house fly (23.3%, MO; 20.9%, DG) pupae. Spalangia spp. were the predominant parasites recovered from field-collected stable fly and house fly pupae on all four dairies. Sentinel house fly pupae placed in fly-breeding sites on both release dairies were parasitized at a significantly higher rate, as compared with sentinel pupae on control dairies. The generic composition of parasites emerging from sentinel house fly pupae was 20.6% Spalangia spp. and 73.2% Muscidifurax spp., whereas in field-collected house fly pupae, Spalangia spp. and Muscidifurax spp. constituted 74.3 and 19.6% of the parasites, respectively.