Behavioural responses to dimethyl disulphide by Aleochara bilineata and Aleochara bipustulata

Adult Aleochara bipustulata L. and Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae) are predatory on immature stages of cabbage root fly Delia radicum (L.) (Diptera: Anthomyiidae). Larvae of the two Aleochara are parasitoids of D. radicum pupae. Female Aleochara lay eggs near D. radicum puparia; the newly‐hatched Aleochara larvae enter puparia and consume the contents. Delia radicum‐infested roots of brassicas give off dimethyl disulphide (DMDS). In the field, DMDS attracts adult Aleochara to pitfall traps but does not enhance the biological control of D. radicum. In the present study, we investigate the behavioural responses of the Aleochara to DMDS in still air, as well as in moving air in a Y‐tube olfactometer, and also investigate the influence of DMDS on host selection. In larvae of both Aleochara species, DMDS induces a restricted‐area search in still air, resulting in elevated frequencies of attack of D. radicum puparia close to a source of DMDS. In the olfactometer, newly‐emerged virgin adults of both sexes of both Aleochara species choose alternatives to DMDS, older recently‐mated females are attracted to DMDS, and older males and older mate‐deprived females show no preference. Mating status of males determines the switch of their response to DMDS from avoidance to indifference. We conclude that DMDS is an important cue for host‐finding, although other cues are involved in mate‐finding. We discuss the implications for use of DMDS to enhance D. radicum mortality and for parasitism of nontarget species if A. bipustulata is introduced to Canada for biological control of D. radicum.     

Interactions between an eucoilid [Hymenoptera] and a staphylinid [Coleoptera] parasitoid of the cabbage root fly

The interaction betweenTrybliographa rapae andAleochara bilineata, 2 parasitoids of the cabbage root fly, is discussed. Larvae ofA. bilineata could not differentiate between cabbage root fly pupae containingT. rapae in its endoparasitic state and unparasitized pupae but could recognize pupae containingT. rapae once the latter had reached its ectoparasitic state. Attack byA. bilineata whileT. rapae was still in its endoparasitic state usually resulted in the staphylinid killing the eucoilid. IfT. rapae had reached the ectoparasitic state before the host pupa was attacked byA. bilineata larvae the eucoilid survived attack by the beetle larva. Multiparasitism, however, resulted in increased levels of mortality of both parasitoid populations.      

Life history comparison between two competitive Aleochara species in the cabbage root fly, Delia radicum: implications for their use in biological control

This study evaluates the efficacy of Aleochara bilineata Gyll and Aleochara bipustulata L. (Coleoptera: Staphylinidae) as biological control agents against the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae). Biological and demographic characters are documented and comparisons made between the two species. The following results were obtained:(1) The reproductive potential and longevity of A. bipustulata females are significantly higher than those of A. bilineata. These differences are correlated with the biology and ecology of the hosts of both species.(2) Under laboratory conditions the rate of increase (r_m) of both staphylinids species is significantly higher than that of the pest and their major competitor Trybliographa rapae West. (Hymenoptera:Figitidae). This may indicate that A. bilineata and A. bipustulata can be effective biological control agents.(3) Aleochara bilineata appears to be the most interesting biological control agent against D. radicum, because of its higher rate of increase, higher host specificity and host acceptance, and a development time which is well synchronised with that of its host. With its higher competitive ability, a population of A. bilineata may increase even if competition occurs. However, A. bipustulata presents interesting biocontrol characteristics, but the best strategy may be only to use the potential of its natural populations.     

Effect of Two Opiine Parasitoids (Hymenoptera: Braconidae) Introduced for Fruit Fly Control on a Native Hawaiian Tephritid,Trupanea dubautiae(Diptera: Tephritidae)

Diachasmimorpha longicaudata(Ashmead) andPsyttalia fletcheri(Silvestri) are opiine parasitoids introduced into Hawaii for control of the Oriental fruit fly,Bactrocera dorsalis(Hendel) and the melon fly,Bactrocera cucurbitae(Coquillett), respectively. Both species have recently been mass-reared and released for research in augmentative biocontrol programs. Laboratory and field sleeve cage experiments were conducted to investigate the potential impact of mass-producedD. longicaudataandP. fletcherion a native Hawaiian tephritid,Trupanea dubautiae(Bryan), infesting the flowerheads of the native composite shrubDubautia raillardioidesHillebrand. Gravid females ofD. longicaudataandP. fletcheriwere confined with bloomingD. raillardioidesflowerheads infested with late instarT. dubautiae.BothD. longicaudataandP. fletcherilacked positive oviposition responses toT. dubautiaelarvae in infested flowerheads and caused neither parasitism nor mortality to the flies. However, when larvae were removed from the flowerheads and presented in screened dishes containing artificial diet of the parasitoids' normal rearing hosts (B. dorsalisandB. cucurbitae), bothD. longicaudataandP. fletcherireadily oviposited in the test larvae. Oviposition byD. longicaudatadid not significantly affect the percentage pupation ofT. dubautiae,but did reduce the emergence of adult flies. Oviposition byP. fletcherisignificantly reduced both pupation and adult fly emergence. All progeny of both parasitoid species died as eggs or first-instar larvae. Results from our experiments demonstrate that biological control programs targeted against frugivorous tephritid pests byD. longicaudataandP. fletcherihave no harmful impact on flowerhead-infestingT. dubautiae.     

Development and encapsulation of the endoparasitoid,Microplitis croceipes (Hym.: Braconidae), in six candidate host species (Lep.)

Encapsulation and development of the endoparasitoid,Microplitis croceipes (Cresson), were studied in six atypical lepidopteran host species whose usual host isHelicoverpa zea (Boddie). The candidate hosts examined were: the fall armywormSpodoptera frugiperda (J. E. Smith); the beet armyworm,Spodoptera exigua (Hübner); the cabbage looper,Trichoplusia ni (Hübner); the greater wax moth,Galleria mellonella (L.); the Indian meal moth,Plodia interpunctella (Hübner); and the diamondback moth,Plutella xylostella (L.). BothS. exigua andT. ni were completely unsuitable forM. croceipes development due to the high rate of eggs that were encapsulated within three days after parasitism. Encapsulation inS. frugiperda included mainly parasitoid eggs and was first detected six days after parasitization at 25°C and two days at 30°C. Encapsulation inG. mellonella occurred only in the larval stage of the parasitoid. InP. interpunctella, parasitoid larvae reached the 3rd stadium, but none of them pupated. OnlyS. frugiperda andG. mellonella supported successful development ofM. croceipes from egg to adult. The percentage of parasitoids reaching the adult stage in these hosts was higher at 30°C than at 25°C (13% vs. 4% inS. frugiperda, and 21% vs. 3% inG. mellonella, respectively). However, these percentages were too low to substitute them as a more economical host for rearingM. croceipes. This biological information will be useful in additional laboratory studies directed toward reducing the rate of encapsulation (e.g., manipulation of host rearing temperature) to increase production ofM. croceipes on these hosts.     

Interspecific discrimination and larval competition amongMicroplitis croceipes,Microplitis demolitor,Cotesia kazak (Hym.: Braconidae), andHyposoter didymator (Hym.: Ichneumonidae), parasitoids ofHeliothis virescens (Lep.: Noctuidae)

Interspecific host discrimination by adults, and larval competition among the endoparasitoidsMicroplitis croceipes (Cresson),Microplitis demolitor Wilkinson,Cotesia kazak (Telenga) andHyposoter didymator (Thunberg) were investigated usingHeliothis virescens (F.) as the host. In ovipositional choice tests, the mean number of encounters and ovipositions for unparasitized hosts was not significantly different from the mean number of encounters and ovipositions for parasitized hosts for each treatment combination (P>0.05). Thus, none of the parasitoid species discriminated between host larvae recently parasitized once by a female of another species und unparasitized hosts. However, in all but two cases, females did discriminate between unparasitized hosts and hosts in which an early first instar of the first-attacking species was developing.Cotesia kazak andH. didymator did not discriminate between unparasitized hosts and hosts parasitized by an early first instar ofM. demolitor. Larval competition among these parasitoid species was studied for three time intervals between the first and second species parasitization: 1) second species attack immediately (5–15 sec) after the first; 2) second species attack 24 h after the first; and 3) second species attack 48 h after the first. Time until egg eclosion was shortest forM. demolitor, thenC. kazak, thenM. croceipes, and longest forH. didymator. When the second parasitoid species attacked a host immediately after the first species, the species in which egg eclosion occurred first was the victor more frequently, except whenM. demolitor competed withC. kazak andH. didymator. With a 24 h delay between the first and second species to attack, the older first instar from the first parasitization usually outcompeted the younger first instar from the second attack. A first instar from the second species to attack generally outcompeted the second instar of the first species when the second parasitization had been delayed 48 h. Competiors were eliminated mainly by physical attack, butC. kazak andM. croceipes apparently also killedH. didymator eggs by physiological processes.     

Rearing phonotactic parasitoid flies [Diptera: Tachinidae,ormiini, ormia spp.]

Females of ormiine tachinids fly to their hosts' calling songs and deposit larvae on the host or nearby. Two species,Ormia ochracea (Bigot) andO. depleta (Wiedemann), were reared for at least 8 generations, making them the first ormiines to be laboratory-propagated. Both were reared on natural hosts:Gryllus spp. field crickets (principallyG. rubens) forO. ochracea, andScapteriscus spp. mole crickets forO. depleta. Commercially rearedAcheta domesticus tested as hosts were less satisfactory. Hosts were parasitized manually or by confinement with flies or planidia (infective larvae). Transparent, cylindrical, sleeved cages were designed to accommodate parasitized hosts and pupae and adults ofO. ochracea. Cages were joined to allowO. ochracea to cycle through its stages with minimum handling and care. Parasitized hosts and pupae ofO. depleta were held in containers of damp sand; adults were held in cages developed forO. ochracea. Adults of both species were maintained on applesauce, sugar cubes, powdered milk, and water. The life cycle ofO. ochracea was about 31 days and ofO. depleta about 36 days, with the principal difference being the time required for planidia to complete development. InO. ochracea the adults emerged synchronously but inO. depleta males preceded females. In both species sex ratio was generally I: 1 and females lived slightly longer than males.O. depleta from our laboratory colony have been released for biological control of mole crickets.      

Native parasitoids associated with the genusAnastrepha (Dipt.: Tephritidae) in Los Tuxtlas,Veracruz, Mexico

In this paper we record the native parasitoids associated withAnastrepha fruit flies collected in a native tropical community from Los Tuxtlas, Veracruz, Mexico. A total of 1600 puparia ofAnastrepha were recovered from infested fruits of ten different host plants. From these puparia we obtained 218 Hymenopteran parasitoids representing the following species:Doryctobracon areolatus (Szépligeti),Utetes (Bracanastrepha) aff.anastrephae (Viereck),Doryctobracon crawfordi (Viereck),Opius hirtus (Fischer),Microcrasis n. sp.,Nealiolus n. sp. (all Braconidae);Odontosema n. sp. andLopheucoila sp. (Cynipidae). The most abundant and frequently encountered parasitoid species observed during this study wasD. areolatus, representing 59.2% of all recovered parasitoids. The analysis of different infestation rates in fruits regarding to degree of parasitization in theseAnastrepha species suggest they are not correlated, meanwhile some host plant characteristics such as fruit size, could play an important role in influencing rates of parasitization.     

Insect-crop interactions in a diversified cropping system: parasitism by Aleochara bilineata and Trybliographa rapae of the cabbage root fly, Delia radicum, on cabbage in the presence of white clover

Parasitism of the cabbage root fly, Delia radicum (L.) by the staphylinid Aleochara bilineata Gyllenhal and the cynipid Trybliographa rapae Westwood was examined in a cabbage monoculture and a mixed stand of cabbage undersown with white clover. Number of overwintering cabbage root fly pupae per plant was consistently reduced in the mixed stand, and the incidence of plants attacked by cabbage root fly was either reduced or not different in the mixed stand compared to cabbage monoculture. For both parasitoids, the probability of D. radicum attacked plants having at least one parasitized pupa increased with density of cabbage root fly pupae around the plant. For A. bilineata, this positive relation between presence of parasitism and host density was consistently stronger in cabbage monoculture than in cabbage undersown with clover. Location of a host plant by T. rapae was not consistently affected by the presence of clover. D. radicum attacked plants situated in the cabbage and clover mixture were found by T. rapae as easily as in cabbage monoculture. Overall, the total risk of parasitism for a cabbage root fly pupa by A. bilineata was reduced in the mixed stand compared to the cabbage monoculture, whereas the risk of parasitism by T. rapae was not consistently affected by clover. For both parasitoids, intensity of parasitism showed a variable relationship with host density on individual plants attacked by the cabbage root fly. Overall, in spite of consistently lower total density of pupae in the mixed cabbage—clover than in cabbage monoculture, the density of unparasitized pupae was reduced by the presence of non-host plants only in two of the four experiments. The results emphasize the need to include not only herbivore and crop, but also other plant species as well as natural enemies when evaluating management methods.     

Comparative study of the antennal sensilla of five species of root maggots: Delia radicum L., D. floralis F., D. antiqua Mg., D. platura MG. (Diptera : Anthomyiidae) and Psila rosae F. (Diptera : Psilidae)

A comparative study of the antennal sensilla of Delia radicum L., D. floralis F., D. antiqua Mg., D. platura Mg. (Diptera : Anthomyiidae) and Psila rosae F. Diptera Psilidae) is undertaken. For both sexes of each species, the type, distribution, and density of sensilla are determined. All 5 species have trichoid (olfactory) and grooved (olfactory) sensilla. Basiconica I (blunt) sensilla (olfactory) are found on each of the species examined, except D. platura. Basiconica II (tapered) (olfactory) and clavate (olfactory) sensilla are found only on Delia species. Also, only Delia species have single-chambered, dorsal pits, and these contain basiconic II pit sensilla (olfactory). Common to all 5 species is a multi-chambered ventral pit (olfactory). In the ventral pit, all 5 species have grooved pit sensilla (olfactory). In addition to this type of sensillum the Delia species have smooth-walled conical pit sensilla (hygro-/thermosensitive) and P. rosae has granular pit sensilla (hygro-/thermosensitive). Smooth-walled tapered pit sensilla (hygro-/thermosensitive) are found in D. radicum. Similarities and differences in the density of surface sensilla between dorsal and ventral funicular surfaces, male and female flies, and oligophagous (D. antiqua, D. radicum, D. floralis and P. rosae) and polyphagous (D. platura) species are compared. Several differences in sensillum density between the dorsal and ventral funicular surfaces are observed, but these do not fit into a consistent trend. Except for D. radicum, there are differences in sensillum density between male and female flies. For the oligophagous species, females have a greater sensillum density, whilst for the polyphagous D. platura males have a greater sensillum density. Comparisons between species show the greatest differences between the Delia species and P. rosae, and within the 4 Delia species, differences in sensillum density do not correlate with host range or body size.     

Fruit infesting tephritids [Dipt.: Tephritidae] and associated parasitoids in Chiapas,Mexico

A total of 1,302 parasitoids representing 8 species and 4 families were recovered from 9,818 fruit fly host fruits sampled. The most common parasitoid species wasDiachasmimorpha longicaudata (Ashmead). Average percent parasitism ranged between 0.44 and 29.23%. Parasitoid emergence data indicate thatAnastrepha ludens (Loew),A. obliqua (Sein),A. serpentina (Wiedeman),A. striata (Schiner) andToxotrypana curvicauda (Gerstaecker) were subject to parasitism. We provide information on the population fluctuation ofAnastrepha ludens, A. obliqua, A. serpentina, A. distincta (Greene),A. striata, A. fraterculus (Wiedeman),A. chiclayae (Greene),A. montei (Costa Lima),A. leptozona (Hendel) andA. tripunctata (Wulp).Anastrepha ludens andA. obliqua were the most common species, representing 95.3% of all fruit fly species caught in McPhail traps.      

Laboratory studies of host finding,acceptance and suitability of the dung-breeding fly,Haematobia thirouxi potans [Dipt.: Muscidae], byAleochara sp. [Col.: Staphylinidae]

Aleochara sp. from southern Africa is a potential candidate for introduction to Australia for control of the Australian buffalo fly,Haematobia irritans exigua De Meijere. Aspects of its host searching and acceptance behaviour were studied in South Africa usingHaematobia thirouxi potans (Bezzi), to assess, in part, its potential value as a biological control agent and to provide a basis for the development of a mass rearing technique. First instars ofAleochara sp. were found to parasitize most effectively those hosts that had buried themselves in the substrate, probably by orienting to a chemical cue and using the tunnels made by the post-feeding larvae. Lower rates of parasitization occurred in pupae placed on the surface of the substrate or buried by the experimenters. They would accept, parasitize and develop on all ages ofH. thirouxi potans pupae, but showed reduced survival in the very oldest ones. Although there was no difference in relative acceptability among hosts of different ages, a higher proportion of younger hosts were parasitized when these had buried themselves, probably due to a tendency of the parasitoids to follow fresher tunnels into the substrate. Survival was high (>80%) at relative humidities from 10–91% but was less than 20% at an R.H. of 100%. In rearing trials, the most economical ratio of parasitoid eggs: hosts was 1∶1.5, with 70% of the parasitoids developing successfully to adults.      

Parasitism of the apple maggot,Rhagoletis pomonella,infesting hawthorns in Washington

Five species of larval parasitoids were reared fromRhagoletis pomonella (Walsh) infested fruit of hawthorn,Crataegus, collected from several locations in southwest Washington over a four year period. A braconid,Biosteres melleus (Gahan), parasitized larvae infesting fruits of a native hawthorn species,Crataegus douglasii Lindl. Another braconid,Opius downesi Gahan, emerged exclusively fromR. pomonella pupae reared from fruits of an introduced species of hawthorn,Crataegus monogyna Jacq. A pteromalid,Pteromalus sp., and two eulophids,Tetrastichus spp., attackedR. pomonella larvae infesting fruits of both hawthorn species. No parasitoids emerged from a total of 4385 pupae reared from apple. Percent parasitism ofR. pomonella was higher inC. monogyna compared toC. douglasii fruits. The highest average levels of parasitism ofR. pomonella inC. monogyna andC. douglasii fruits were 90% and 23% respectively. The kinds of parasitoids, their relative abundances and timing of parasitization on the two hawthorns was related to differences in fruit ripening patterns and its effect on the development ofR. pomonella on these two hosts. Parasitization ofR. pomonella byTetrastichus spp. is a new host record. The detection of these species andPteromalus sp. in southwest Washington are the first records of ectoparasitoids attacking this tephritid.     

Host habitat finding and host selection of theDrosophila parasitoidLeptopilina australis (Hymenoptera,Eucoilidae), with a comparison of the niches of EuropeanLeptopilina species

Summary Decaying petioles of giant hogweed,Heracleum mantegazzianum Sommier & Levier, are used as a breeding site by six species ofDrosophila and the drosophilidScaptomyza pallida. The most numerous parasitoid species associated with this community isLeptopilina australis. BecauseL. australis was previously unknown in western Europe, we present the characters to distinguish it form its close relativeL. clavipes. Experiments on host species selection and survival ofL. australis showed that this parasitoid mainly usesD. limbata as host. Olfactometer experiments showed thatL. australis is attracted by the odour of decaying hogweed stalks, especially when these contain larvae ofD. limbata. L. australis is also strongly attracted by the odour of stinkhorns, a habitat in which it has never been found in nature.D. phalerata is the dominant fly species in stinkhorns, and is not a host ofL. australis. We offer a possible functional explanation for this unexpected habitat choice, by showing thatD. transversa andD. kuntzei, both species found to breed in fungi, are also suitable hosts forL. australis. We also discuss habitat choice with regard to a proposed phylogeny of theLeptopilina species in temperate Europe. Finally, we discuss niche overlap ofL. australis with the otherLeptopilina species.     

Evolution of thedec-1 eggshell locus inDrosophila. I. Restriction site mapping and limited sequence comparison in themelanogaster species subgroup

Summary We have analyzed 18 kb of DNA in and upstream of thedefective chorion-1 (dec-1) locus of the eight known species of themelanogaster species subgroup ofDrosophila. The restriction maps ofD. simulans, D. mauritiana, D. sechellia, D. erecta, andD. orena are shown to have basically the restriction map ofD. melanogaster, whereas the maps ofD. teissieri andD. yakuba were more difficult to align. However, the basic amount of DNA and sequence arrangement appear to have been conserved in these species. A small deletion of varying length (65–200 bp) is found in a repeated sequence of the central transcribed region ofD. melanogaster, D. simulans, andD. erecta. Restriction site mapping indicated that thedec-1 gene is highly conserved in themelanogaster species subgroup. However, sequence comparison revealed that the amount of nucleotide and amino acid substitution in the repeated region is much larger than in the 5 translated region. The 5 flanking region showed noticeable restriction site polymorphisms between species. Based on calculations from the restriction maps a dendrogram was derived that supports earlier published phylogenetic relationships within themelanogaster species subgroup except that theerecta-orena pair is placed closer to themelanogaster complex than toD. teissieri andD. yakuba.     

Costs of reproduction and geographic variation in the reproductive tactics of the mosquito Aedes triseriatus

Intraspecific host discrimination is widespread in solitary parasitoids whose adult females forage for and evaluate host suitability, whereas interspecific discrimination is less common. In some parasitoid species, mostly Diptera and Coleoptera, the larva performs the last step of host searching. It has been suggested that host discrimination will rarely occur in such host-seeking larvae because their low mobility results in a low host encounter rate. We determined the extent to which the larvae of Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae), a solitary parasitoid of aggregated Diptera pupae: (1) discriminated between unparasitized hosts and hosts parasitized by conspecifics; (2) used semiochemical cues to discriminate; (3) were influenced by life expectancy, presence of conspecifics and host availability in their host acceptance decision; and the extent to which (4) A. bilineata and A. bipustulata L., a species exploiting the same hosts and occurring sympatrically, showed interspecific host discrimination. A. bilineata larvae were able to discriminate between unparasitized hosts and hosts parasitized by conspecifics in a choice experiment. Such behavior has never previously been described for a coleopteran parasitoid or for a parasitoid species whose larvae perform host searching. Host discrimination in this species was not based on the presence of visual or tactile cues (e.g., entrance holes) but rather on chemical cues. The life expectancy of A. bilineata larvae was significantly shorter in the presence than in absence of hosts, and older larvae had lower parasitism success than young larvae in a 24-h experiment. However, the host acceptance decision of A. bilineata larvae was not influenced by larval age or the presence of conspecifics when the ratio of hosts per larva was greater than or equal to 1. When hosts were scarce, the degree of superparasitism increased significantly with the number of foraging conspecifics and the age of the larvae. Both species of Aleochara showed intra- and interspecific host discrimination in a choice experiment. In contrast to A. bipustulata, A. bilineata larvae more frequently parasitized hosts parasitized by A. bipustulata than those parasitized by conspecifics. We suggest that host discrimination will be frequent in solitary parasitoids with host-seeking larvae when hosts are aggregated. Received: 4 June 1998 / Accepted: 1 September 1998     

Female-derived sex pheromone mediates courtship behaviour in the parasitoid Lariophagus distinguendus

Brassiceye^®traps baited with ethylisothiocyanate were modified and used to collect live adults of Delia radicum(L.) and Delia floralis(Fallén) (Diptera: Anthomyiidae) from the field to observe the prevalence of Entomophthora muscae(Cohn) Fresenius and Strongwellsea castransBatko & Weiser. The traps were highly effective and selective for D. radicumand D. floralis. Of the flies identified, 98.4% in 1996 and 93.7% in 1997 were either D. radicumor D. floralis. In 1997 the maximum mean catch was as high as 82 flies per trap per day, and more than 80% of these were females.During both seasons E. muscaecaused relatively high levels of mortality in adult populations of D. radicumand D. floralis. The fungus caused a total infection level of 17.9% in 1996 and 47.7% in 1997 with infection peaks of 82.4% in 1996 and 87.5% in 1997. Both years, a significant positive correlation was found between E. muscaeprevalence and temperature. One infection peak was observed for S. castransin 1996, and during that season the total S. castransinfection level was 18.0%. In 1997, the total S. castransinfection level was as low as 8.1%. There is no strong indication that the prevalence of E. muscaeor S. castransdiffers between either the fly species or sexes within species.     

The effect of the dung pad fauna on the emergence ofMusca tempestiva [Dipt.: Muscidae] from dung pads in southern France

The emergence ofMusca tempestiva Fallèn, from cow pads in southern France was reduced by a mean of 98% and 96% respectively in nine experiments concluded in 1979 and 1981, by the action of the complete dung fauna. Fauna emerging from dung pads and captured in simultaneous trapping using dung baited pitfall traps consisted of 13 Dipterous species (9 Muscidae, 2 Sepsidae and 2 Sphaeroceridae), 25 Coleopterous species (7 Scarabaeidae, 1 Geotrupidae, 2 Aphodiidae, 3 Hydrophilidae, 12 Staphylinidae), 3 Hymenopterous parasites and 1 species of macrochelid and 2 species of parasitoid mites carried phoretically by the dung beetles. The total number of insects and mites per trap was usually small. The Staphylinidae which included 4Aleochara species of whichAleochara tristits Gravenhorst andA. bipustulata (L.) are known parasitoids of Diptera pupae, and 6 predatory species, were the most abundant insects present. Whilst the overall abundance of insects and mites trapped was relatively low it is probable that the most important factor in the control ofM. tempestiva was the combined influence of the different elements making up the dung pad fauna.     

Dispersal ofAleochara bilineata [Col.: Staphylinidae] following inundative releases in urban gardens

Aleochara bilineata (Gyllenhal) [Coleoptera: Staphylinidae] is a common predator and endoparasite of root maggot [Diptera: Anthomyiidae] in both commercial crops and home gardens. To test dispersal activity ofA. bilineata in home gardens, marked beetles were released at rates of 0 and 1,000 in 1987 and 0, 250, 500, and 1,000/gardens/wk in 1988. Three percent of marked beetles were recaptured in release gardens. NaturalA. bilineata populations were very small in all gardens, and there was no detectable increase from 1987 to 1988. Recaptures were proportional to release rates. There was no significant difference in recapture rates between sexes. Recaptures and non-uniform distributions of markedA. bilineata in control gardens revealed that they were capable of flying at least 5 km under urban conditions, and of selecting particular gardens as suitable mating, foraging, and oviposition sites.      

Dryinid (Hym.: Dryinidae) parasitoids ofDalbulus leafhopper (Hom.: Cicadellidae) in Mexico

Little is known about the natural enemies of the leafhopperDalbulus spp. (Homoptera: Cicadellidae). Searches for its dryinid (wasps) parasitoids were made in Jalisco, Mexico. Jalisco contains the greatest number ofDalbulus species, and is considered to be near to the center of origin of this leafhopper genus and its host plants: maize, teosintes (Zea spp.) and gamagrasses (Tripsacum spp.). The dryinidGonatopus bartletti was found parasitizingD. maidis on maize and on annual teosinteZea mays spp.parviglumis. G. flavipes was found parasitizingD. elimatus on perennial teosinteZ. perennis; and a new speciesG. moyaraygozai andAnteon ciudadi parasitizingD. quinquenotatus onTripsacum pilosum andT. dactyloides. Parasitism by dryinids was found at altitudes of 680–2,000 m.Dalbulus maidis, the leafhopper species which causes the greatest losses in maize in Latin America, was found to be parasitized from 680–1,760 m. TheDalbulus species associated with annual host plants (maize andZ. mays spp.parviglumis) were parasitized by dryinids during the rainy season, while theDalbulus species associated with perennial host plants (Z. perennis andTripsacum) were parasitized by dryinids during both the rainy and dry season. The greatest diversity of dryinid parasitoids ofDalbulus spp. and the highest levels of parasitism were recorded from perennial plants, indicating that such species are reservoirs of natural enemies ofDalbulus spp.