Parasetigena silvestris

(Robineau-Desvoidy, 1863)

Parasetigena silvestris is a tachinid fly and of the gypsy moth (Lymantria dispar). Females deposit macrotype directly onto larvae, with strong selectivity for host instar—first instars are rejected, while second through fifth instars are accepted with increasing preference for larger hosts. The exhibits a bimodal diel activity pattern with oviposition peaks in early morning and late afternoon. It locates hosts by searching vegetation and responds to host silk trails and as orientation cues. occurs in the field, with parasitoid eggs aggregated on certain hosts rather than randomly distributed.

Pronunciation

How to pronounce Parasetigena silvestris: //ˌpærəˌsɛtɪˈdʒiːnə sɪlˈvɛstrɪs//

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Habitat

Forested areas with gypsy moth ; specifically observed in Connecticut woodlands. structure influences oviposition patterns, with differential rates reported between larvae collected from under burlap bands versus elsewhere in the same forest plot.

Distribution

North America, including the conterminous United States; records from Denmark, Norway, and Sweden suggest broader Holarctic distribution. Native to Europe, introduced to North America where it has established as a agent of the gypsy moth.

Host Associations

Lymantria dispar - larval ; second through fifth instars parasitized, first instars rejected. Oviposition selectivity increases with size.

Life Cycle

Females deposit macrotype on larvae; larval development occurs internally within the host. has been observed in the field, with multiple eggs sometimes deposited on single hosts. In laboratory conditions, increased superparasitism elevates and host mortality, but reduces individual parasitoid survival probability and puparial size.

Behavior

Bimodal diel activity pattern with distinct peaks in early morning and late afternoon. location involves vegetation searching and response to host silk trails and as orientation cues. Attack rates increase with host . Oviposition is non-random and influenced by host behavioral state. Females demonstrate active host selection based on instar and size.

Ecological Role

agent regulating gypsy moth in forest . As a larval , it contributes to mortality of this significant forest pest. Field patterns suggest that sampling methods (e.g., burlap band collections) may underestimate true parasitoid impact on populations.

Human Relevance

Intentionally introduced and established in North America for of the gypsy moth, an forest pest. Used in programs. Sampling methodology considerations are important for accurate assessment of efficacy—larvae from burlap bands may yield biased estimates of impact.

More Details

Superparasitism dynamics

Field studies indicate that P. silvestris are aggregated on certain rather than randomly distributed, meaning some larvae experience disproportionately high . This is more pronounced when hosts are collected from under burlap bands, potentially skewing impact assessments.

Host instar trade-offs

Fifth-instar gypsy moth larvae yield higher survival probability than fourth instars, but produce smaller . This suggests a trade-off between quality and parasitoid offspring size.