Ability of Spalangia endius (Hymenoptera: Pteromalidae) to Parasitize Bactrocera dorsalis (Diptera: Tephritidae) after Switching Hosts

We studied the parasitism capacity of Spalangia endius as a pupal parasite of Bactocera dorsalis after switching hosts. We used pupae of B. dorsalis and M. domestica as the hosts and studied parasitism by S. endius in the laboratory. The parasitism capacities were compared at different host densities and different parasitoid ages. The two functional responses of S. endius fitted a Holling Type II equation. More M. domestica were parasitized than B. dorsalis at all the densities. The ability of S. endius to control M. domestica was α/Th (parasitism capacity) = 32.1950, which was much stronger than that of control B. dorsalis, which was α/Th = 4.7380. The parasitism rate of wasps that had parasitized B. dorsalis had decreased by the emergence time of parasitoids. These results suggest that the parasitoid-pest ratio should be 1:25 to maintain a relatively stable parasitism rate for control of B. dorsalis. The S. endius colony reared on M. domestica successfully controlled a low-density population of B. dorsalis in the lab. We provide evidence suggesting that the parasitism capacity of S. endius needs to be improved.

Niche differentiation of two pupal parasitoid wasps of Musca domestica (Diptera: Muscidae): Pachycrepoideus vindemmiae and Spalangia endius (Hymenoptera: Pteromalidae)

In nature, competing species often achieve coexistence through niche differentiation. We examined this phenomenon for Pachycrepoideus vindemmiae and Spalangia endius (Hymenoptera: Pteromalidae), two species of pupal parasitoids that are considered biological control agents of house fly, Musca domestica (Diptera: Muscidae). We examined the ability of each species, alone and in combination, to locate host pupae buried at different depths (0, 1, 2, 4, and 6 cm) in three types of substrate (sand, dry wheat bran, and spent fly diet). We then evaluated the competitiveness of each species by allowing first one species, then the other species, to parasitise host individuals within time periods ranging from less than 2 hours to 96 hours of each other. Spalangia endius exhibited greater ability than did P. vindemmiae to locate host pupae buried at depths below one centimetre. Conversely, P. vindemmiae exhibited a greater competitive ability, being more likely to emerge from pupae co-parasitised by S. endius, regardless of oviposition interval or sequence. Our findings suggest that these two parasitoid species coexist through niche differentiation. Our findings also indicate that to increase the effectiveness of biological control, the environmental conditions and risk of interspecific competition should be considered when selecting parasitoid species for release.

Annotated checklist and illustrated key to parasitoids (Hymenoptera: Diapriidae, Eulophidae and Pteromalidae) of fruit flies (Diptera, Tephritidae) in Brazil

The hymenopteran parasitoids of pest species of Tephritidae in Brazil are best known by their most prominent species, members of Braconidae and Figitidae. Species in the less-studied families Diapriidae, Eulophidae and Pteromalidae, which are mostly pupal parasitoids, have been largely neglected and the literature on these groups is sparse and scattered. Therefore, their importance as natural enemies of fruit flies is likely underestimated. Here, we present a parasitoid-host-plant checklist of all diapriids, eulophids and pteromalids that parasitize fruit flies of economic importance in Brazil, namely Anastrepha species and Ceratitis capitata. A compilation of information of the seven species of these parasitoids occurring in Brazil—Coptera haywardi Loiácono and Trichopria anastrephae Lima (Diapriidae), Tetrastichus giffardianus Silvestri (Eulophidae), Pachycrepoideus vindemmiae (Rondani), Spalangia endius Walker, S. gemina Bouček and S. simplex Perkins (Pteromalidae)—including their taxonomic status, general biology, and potential as biocontrol agents, is presented. Additionally, we provide an illustrated key to species, aiming to highlight key morphological features and facilitate identification at species level, stimulating future research on these groups.

A Field-Relevant Concentration of the Insecticide Imidacloprid Affects Grooming, Locomotion, and Longevity in the Biological Control Agent Spalangia endius (Hymenoptera: Pteromalidae)

Foreign materials like insecticides may increase grooming in insects; and generally, grooming may be expected to reduce effects of insecticides, but this may not be the case when grooming involves the mouth and hence a risk of ingestion. To examine this, female Spalangia endius, a wasp that parasitizes filth fly pupae, were exposed to a surface coated with a low concentration of imidacloprid or not. Their mouthparts were sealed or not to determine whether sealing is a useful method for examining effects of mouth grooming. Wasps mouth-groomed more frequently while exposed to imidacloprid than when not. However, imidacloprid did not increase the number of times that a wasp groomed the rest of her body, and this was true regardless of whether or not her mouthparts were sealed. While exposed to imidacloprid, wasps spent less time locomoting only if their mouthparts were not sealed. Having been exposed to imidacloprid also decreased subsequent longevity, from 9 to 7 d. These effects of imidacloprid on grooming, locomotion, and longevity occurred despite exposure being for just 5 min and to only 2% of the amount that will be present in an area immediately after house fly baits are scattered at their recommended coverage. This is such a low amount that, with 48 h of constant exposure, mortality of these wasps is only 10%. Having mouthparts sealed decreased locomotion and longevity regardless of exposure to imidacloprid. Thus, sealing mouthparts is not useful for measuring effects of mouth grooming.