Anastrepha Ludens Larvae Research Articles

Host-specific demography of Utetes anastrephae (Hymenoptera, Braconidae), a native parasitoid of Anastrepha spp. fruit flies (Diptera, Tephritidae)

The braconidUtetes anastrephae(Viereck, 1913) (Hymenoptera: Braconidae) is a larva-pupal parasitoid of fruit flies of the genusAnastrephaSchiner, commonly associated withAnastrepha obliqua(Macquart, 1835) (Diptera: Tephritidae), the most important pest of mango (Mangifera indicaL., 1753) in Mexico. This parasitoid was established in a laboratory colony using larvae ofAnastrepha ludens(Loew, 1873) as host. Here we describe a demographic study to compare the reproductive and population parameters of this parasitoid reared onA. obliquaandA. ludensunder laboratory conditions. TwoU. anastrephaecohorts of 30 individual pairs each were set up, one was reared onA. obliqualarvae and the other one onA. ludens. Every day, 30 third instar larvae of each host species were exposed to an adult pair through the lifespan of the female. Daily mortality and fecundity were recorded. Life tables were constructed and sex ratios, parasitism rates, survival, reproductive and population parameters were estimated. Higher survival ofU. anastrephaefemales was observed in females fromA. obliqua(mean live expectancy of 22.4 days), but higher fecundity and parasitism occurred in females fromA. ludens(net fecundity of 62.61 daughters/ female and 16.72% parasitism rate). The intrinsic rate of increase (r= 0.128 andr= 0.134 forA. obliquaandA. ludensrespectively), mean generation time (27.88 and 28.30 days) and population doubling time (5.42 and 5.16 days) were similar in both cohorts, as well as the sex ratio (73 and 69% of females). These results suggest thatA. ludensas host increase the production rates; however, any one of these two species could be used as host for mass rearing purposes.

Superparasitism strategies by a native and an exotic parasitoid species attacking the Mexican fruit fly, Anastrepha ludens (Diptera: Tephritidae)

Superparasitism refers to the action of parasitoids ovipositing eggs in hosts that are already parasitized; this inevitably results in the elimination of supernumerary larvae in solitary parasitoids. Here, we investigated superparasitism performed by two species of solitary parasitoids on the larvae of Anastrepha ludens (Loew; Diptera: Tephritidae): a native species, Doryctobracon crawfordi (Viereck; Hymenoptera: Braconidae), and an exotic species, Diachasmimorpha tryoni (Cameron; Hymenoptera: Braconidae). Tests were conducted under laboratory conditions evaluating the behaviour of females acting alone (self-superparasitism) or in groups (conspecific superparasitism). Parasitism strategies were different between these two species. In D. crawfordi, the number of first instar larvae found in each dissected host pupa was never greater than two, regardless of the number of oviposition scars observed per pupa. In contrast, there was a positive correlation between the number of oviposition scars and the number of first instar larvae in D. tryoni. The survival and fecundity of D. crawfordi females emerging from pupae with one scar was higher than in females emerging from pupae with more scars. In D. tryoni, the number of oviposition scars did not show deleterious effects on life history traits and was positively correlated with the proportion of emerging females. An understanding of the superparasitism strategy adopted by parasitoid species could be of great interest to augmentative biological control programmes because the mass rearing of natural enemies could be negatively or positively affected by this condition.

Parasitism by Coptera haywardi and Diachasmimorpha longicaudata on Anastrepha flies with different fruits under laboratory and field cage conditions

Larvae of Anastrepha ludens and A. serpentina that developed in mango and sapodilla fruits, respectively, were exposed to Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) and sequentially exposed as pupae to Coptera haywardi (Oglobin) (Hymenoptera: Diapriidae). Sequential exposure to both parasitoid species contributed to a decrease in fruit fly emergence due to higher levels of parasitism, which varied according to fruit type. In creole mango, D. longicaudata represented the highest percentage of parasitism. C. haywardi parasitism was greater in pupae from Ataulfo mangos and sapodilla, where the pulp size and volume may have acted as a refuge, allowing fly larvae to escape and leaving a greater number of unparasitised pupae available to C. haywardi. Similar results were obtained under field cage conditions, but the level of parasitism by C. haywardi was lower, suggesting that its effectiveness has some limitations under natural conditions. Our results suggest that both species can exert complementary parasitism, which represents an alternative worth to investigate under open field conditions.

Foraging behavior by six fruit fly parasitoids (Hymenoptera: Braconidae) released as single- or multiple-species cohorts in field cages: Influence of fruit location and host density

In Mexico, both native and exotic fruit fly parasitoids exhibit spatial and temporal overlaps in distribution. To better characterize the spatial component of foraging in the braconid portion of this guild, and to examine the effects of intra- and interspecific competition on resource partitioning, we conducted two field-cage experiments aimed at: (1) assessing the host-finding ability of parasitoids when single- or multiple-species cohorts were confronted with very low host-densities only at canopy level; (2) determining the height level preference (canopy vs. ground) for parasitoid foraging activity when single- or multiple-species cohorts were present and host density was high; (3) identifying candidate species for biological control programs using multiple-species releases. We studied two species exotic to Mexico, Diachasmimorpha longicaudata and D. tryoni, and four species native to Mexico, Doryctobracon areolatus, D. crawfordi, Opius hirtus, and Utetes anastrephae (all Braconidae, Opiinae). Parasitoids were allowed to forage for 8-h as single- or multiple-species cohorts in a room-sized cage containing potted trees with guavas artificially infested with Anastrepha ludens larvae and attached to the branches. When parasitoids were released as single-species cohorts into low host-density environments (fruit only at canopy level), D. longicaudata, D. tryoni and O. hirtus clearly distinguished uninfested from infested fruit and exerted the highest rates of parasitism with a significantly female-biased offspring sex ratio. When multiple-species cohorts were released, the same pattern was observed but, D. crawfordi and D. areolatus did not parasitize any larvae. In the case of the high host-density condition and with fruit at canopy and ground levels, when parasitoids were released in single-species cohorts, only D. crawfordi and D. longicaudata parasitized larvae at ground level. At canopy level, D. longicaudata, D. tryoni and D. crawfordi achieved the highest parasitism rates. When parasitoids were released as multiple-species cohorts, individuals of none of the species foraged at ground level, and in the canopy foraging activity and parasitism rates dropped dramatically in all species, except O. hirtus. Given the performance of O. hirtus, it should be considered a potential candidate to complement D. longicaudata in low-host density prevalence areas.

Functional Response and Superparasitism by <I>Diachasmimorpha longicaudata</I> (Hymenoptera: Braconidae), a Parasitoid of Fruit Flies (Diptera: Tephritidae)

The functional response and the effect of superparasitism of Diachasmimorpha longicaudata (Ashmead) in larvae of Anastrepha ludens (Loew) was determined under laboratory conditions. Adult parasitoids were tested individually and in groups of 5. Third-instar A. ludens larvae were exposed for 3 h to experienced, 5-d-old females at the ratios of 1, 5, 20, 30, 40, 50, and 60 host larvae per wasp. For individual females, functional response was type III, whereas for females in groups, a type II curve was observed. In the presence of conspecifics, females increased their parasitization activity. Females showed a strong tendency for self-superparasitism (the same female laying >1 egg in the same host) with a range of 38.9-57.9% of larvae superparasitized, even when there was no competition and a high availability of host larvae. In the superparasitism experiment, when the parasitoid/host ratio was 1 or greater, larval mortality was consistently high but never exceeded 90%. Successful parasitoid emergence decreased as the parasitoid/host ratio increased. We discuss and question the detrimental effects that have been attributed to superparasitism in solitary endoparasitoids.