Megastigmus spermotrophus (Torymidae)
Douglas-fir seed chalcid
||Females are amber coloured wasp-like insects, about 4.0
mm long, with a long ovipositor which curves up over the abdomen. Males are
lighter in colour, almost yellow, about 3.0 mm long (as seen in photo).
||White, legless grubs, complete whole development inside
a single seed.
||Female chalcids deposit an egg into each seed selected in
a young cone by means of her ovipositor, no entry marks are made by the
ovipositor. The larvae feed only on seed contents, each one destroying a
single seed. After devouring the contents it remains within the seed coat.
There is no external evidence of damage until the adult emerges, after which
a clearly defined emergence hole is evident. Prior to adult emergence insect
damage can be detected only by seed dissection or
X-rays. Larvae remain over winter in the seeds, either
in the cone which may remain on the tree, or in the litter. It pupates in
Douglas-fir (Pseudotsuga macrocarpa).
Usually less destructive than
B. colfaxiana and
but can be a problem in seeds destined for export.
References and Links:
EAG: 548, 551;