Racha Djeddai, Noureddine Rahim, Khadidja Mahdi

Comparative analysis of egg batch characteristics, branch preferences, hatching rates, and parasitism in Thaumetopoea bonjeani and Thaumetopoea pityocampa

Abstract In Algeria, two Thaumetopoea species (Lepidoptera: Notodontidae), Thaumetopoea bonjeani (cedar processionary moth, CPM) and Thaumetopoea pityocampa (pine processionary moth, PPM), coexist in Cedrus atlantica forests causing significant tree damage and posing health risks to humans. This study investigates key bioecological differences between these species, which share similar environmental conditions, by comparing their reproductive potential, with a focus on fecundity, egg batch characteristics, and mortality factors. A total of 125 egg batches were collected from C. atlantica in two cedar forests: 75 batches of T. pityocampa were collected from Chréa forest and 50 batches of T. bonjeani from Tala-Guilef forest. The PPM showed significantly higher fecundity, with an average of 222.68 eggs per egg batch, compared with 135.84 eggs for CPM. Although mean egg batch lengths were similar (~25 mm), PPM females preferred larger branches (2–10 mm diameter) than CPM (2–7 mm). The average number of egg rows per batch was greater in PPM (10.77) than CPM (5.56). Regression analysis revealed positive correlations between egg batch length, egg count, and row number in both species, although branch diameter was significantly correlated only in CPM. Hatching rates were higher for PPM (90.6%) compared to CPM (60.4%), with predation being the primary mortality factor for CPM eggs (17.1%) compared to 1.1% in PPM. Egg parasitism also differed significantly between the species, with Ooencyrtus pityocampae dominating CPM parasitism and Baryscapus servadeii and Trichogramma sp. predominating in PPM. These findings enhance our understanding of species-specific life-history strategies and offer important implications for the development of targeted and ecologically informed pest management approaches in Mediterranean forest ecosystems.

Doi https://doi.org/10.35513/21658005.2025.2.2

Keywords Thaumetopoea pityocampa; Thaumetopoea bonjeani; Cedrus atlantica; fecundity; egg mortality; parasitism; Algeria

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