Seed-parasite
Guides
Megastigmus spermotrophus
Douglas Fir Seed Chalcidoid Wasp, Douglas-fir Seed Chalcid
Megastigmus spermotrophus is a seed-parasitic chalcid wasp native to western North America that has become invasive in Europe and other regions. It specializes in attacking seeds of Douglas-fir (Pseudotsuga menziesii), causing significant economic losses in seed orchards and natural forests. The species exhibits complex life history traits including facultative larval diapause lasting up to three years, which enables population persistence despite fluctuating cone crops. Females oviposit through cone scales into developing seeds, and the species shows preferences for larger cones with strongly arched exteriors and cone tips. Genetic polymorphism in diapause expression allows adaptation to varying environmental conditions.
Megastigmus transvaalensis
Peppertree Seed Chalcid
Megastigmus transvaalensis is a minute chalcid wasp native to South Africa that has become invasive in Mexico, Brazil, and Chile. Adults are yellowish-brown with pronounced sexual dimorphism in size. The species is a seed parasite that targets drupes of Rhus species in its native range and has shifted to Schinus species in South America, with significant implications for biological control and native plant conservation.
Rhinusa antirrhini
toadflax seedhead weevil, toadflax capsule weevil, seed-gall weevil, Toadflax Seed Weevil
Rhinusa antirrhini is a seed-parasitic true weevil (Curculionidae) native to Europe that has been introduced to North America. It specializes on toadflax species (Linaria spp.), particularly Dalmatian toadflax (L. dalmatica) and yellow toadflax (L. vulgaris). Despite intentional redistribution as a biological control agent in the 1990s, it has not proven effective at suppressing invasive toadflax populations. Population genetic studies reveal host-associated genetic differentiation driven by associations with different Linaria species.