Life cycle of a tachinid fly, Erynniopsis antennata. This parasite of elm leaf beetle, Xanthogaleruca luteola, develops through one of two different phases, depending on the season.

SPRING/EARLY SUMMER
A: The parasite spends the winter as young larvae inside overwintering adult elm leaf beetles. B: Erynniopsis completes development after beetles begin feeding on foliage in the spring and adult parasites emerge from adult beetles; this parasite emergence is not readily observed. C: Each fly lays one egg on each of several dozen beetle larvae. Eggs hatch and the parasite larvae enter their host and feed inside. D: During spring and early summer parasitized beetle larvae are killed. Erynniopsis antennata then develop into black to reddish, cylinder- or teardrop-shaped parasite pupae at the tree base among yellowish beetle pupae.

SUMMER/OVERWINTERING
E: As the season progresses, an increasing proportion of the parasite population enters diapause (their inactive, overwintering phase), remaining as immature parasites inside beetle pupae. A: Beetles undergo metamorphosis into overwintering adults. B: Parasites mature and emerge from adult beetles in spring and this cycle repeats. One parasite generation takes several weeks during summer and 6 months or more over winter. Several generations occur each year.

UC IPM. Beetle adult and larva from Anonymous. 1960. USDA Leaflet 184. Adult parasite from Cole FR. 1969. The Flies of Western North America. UC Press. Berkeley, CA. Parasite pupa by Silvestri F. 1910. Contribuzioni alla conoscenza degli insetti dannosi e dei loro simbionti. Bollettino del Laboratorio di Zoolo?ia Generale e Agraria (Portici) 4:246?288. Beetle pupa from Herrick GW. 1913. Control of two elm-tree pests. Cornell Univ. Agric. Exper. Sta. Bull. 333. Ithaca, NY.