No abstract

The neotropical parasitoid Conura annulifera (Walker) (Hymenoptera: Chalcididae) is known to parasitize birdparasitic flies in the genus Philornis (Diptera: Muscidae) including P. downsi (Dodge and Aitken), a species that has invaded the Gal apagos islands and is negatively impacting populations of Darwin's finches. We report here some aspects of the life history, field ecology, and host specificity of C. annulifera. We collected puparia of four Philornis species in 13 bird nests during 2015 and 2016 in western mainland Ecuador and found that C. annulifera and three other parasitoid species emerged from those puparia. This is the first record of C. annulifera in Ecuador. Rearing records and dissections of parasitized puparia revealed that C. annulifera is a solitary pupal ectoparasitoid, placing its eggs in the gap between host pupa and puparium. Laboratory studies of host specificity involving P. downsi and pupae from five other dipteran, three lepidopteran, and one hymenopteran species found that C. annulifera only produced progeny when presented with P. downsi pupae. Pupae of P. downsi that had been exposed to C. annulifera also failed to emerge more often than expected by chance compared with no-parasitoid controls, suggesting that the parasitoids can cause developmental mortality through means other than successful parasitism. These studies constitute the first steps in evaluating C. annulifera as a potential biological control agent of P. downsi in the Gal apagos Islands.

In a study of almost 16 000 nest records from seven swallow species across the entire Western Hemisphere, clutch sizes decline with relative laying date in each population, but the slope of this decline grows steeper with increasing distance from the equator. Late-laying birds at all latitudes lay clutches of similar sizes, suggesting that latitudinal differences may be driven primarily by earlier-laying birds. Focused comparisons of site-years in North America with qualitatively different food availability indicate that food supply significantly affects mean clutch size but not the clutch size-lay date regression. Other studies on the seasonality of swallow food also indicate that steeper clutch size-lay date declines in the North are not caused by steeper earlier food peaks there. The distribution of lay dates grows increasingly right-skewed with increasing latitude. This variation in lay-date distributions could be due to the predominance of higher quality, early-laying (and large-clutched) individuals among populations at higher latitudes, resulting from latitudinal variation in mortality rates and the intensity of sexual selection. Our results underscore the importance of studying clutch size and lay date in tandem and suggest new research into the causes of their joint geographic variation.