Phenological responses of Pseudomallada (Neuroptera: Chrysopidae): Comparative data from three Nearctic species and interspecific hybrids

Abstract

Three Nearctic species - Pseudomallada macleodi (Adams & Garland), P. perfectus (Banks), and P. sierra (Banks) - share a suite of phenological characteristics with their Western Palearctic congeners. They overwinter as free-living larvae (primarily third instars) in a photoperiodically induced diapause. For these three species, the critical photoperiods for diapause induction fell between LD 16:8 and LD 14:10. In the laboratory, larvae remained responsive to daylength throughout diapause - short daylengths maintained diapause until diapause terminated spontaneously or death occurred. Transfer of diapausing larvae from short to intermediate or longer days accelerated diapause development, apparently in a quantitative response to daylength. A period of chilling appeared to delay, rather than hasten, diapause development. In general, the expression of diapause in F1 hybrids (P. perfectus × P. sierra) resembled that of the parents; there were minor differences in some features. Among populations of the three species under non-diapause conditions, the times for complete development (egg hatch to adult emergence) ranged between 40 and 50 days (23.9°C). Under long-day conditions, developmental rates of the P. perfectus egg and prepupal-pupal stages were linearly related to temperature; we provide thermal thresholds and heat-degree days for these stages. In contrast, developmental rates of free-living larvae did not have a linear relationship with temperature; photoperiod may interact with temperature to affect non-diapause development in these stages.

Keywords

• neuroptera
• chrysopidae
• pseudomallada spp.
• larval diapause
• photoperiod
• temperature and development
• quantitative response to daylength