Mj. Mckone et al., Biology of insects that feed in the inflorescences of Chionochloa (Poaceae) in New Zealand and their relevance to mast seeding, NZ J ZOOLOG, 28(1), 2001, pp. 89-101
Inflorescences of New Zealand Chionochloa species are attacked by at least
three insects, two flies and a moth. There has been disagreement about the
identity of various life stages of these insects. We followed the seasonal
pattern of occurrence of the two fly species that fed in Chionochloa pallen
s inflorescences in a population on Mt Hutt, Canterbury. Eggs and larvae of
Diplotoxa similis (Diptera: Chloropidae) appeared in the inflorescences as
soon as they emerged. The larvae are principally flower feeders, and most
D. similis individuals had pupated by the end of the flowering period. Dipl
otoxa similis adults emerged from the puparia at the end of the season, and
probably overwintered as adults. The second fly was an undescribed cecidom
yiid (Diptera: Cecidomyiidae). Eggs of the cecidomyiid are laid into the C.
pallens florets at the time of flowering, and hatch into mobile, transluce
nt, early-instar larvae. Late-instar larvae were less mobile and opaque ora
nge. and probably dropped from the inflorescences late in the season. The t
hird species, Megacraspedus calamogonus (Lepidoptera: Gelechiidae) has larg
e mobile caterpillars which appear early in the season, but there is doubt
about its egg morphology and oviposition sites. On two dates there was a ne
gative correlation between densities of the two fly species among plants. S
ince D. similis appears first, it may be able to usurp resources and reduce
densities of the cecidomyiid. A review of known occurrences of the three i
nsects suggests that. compared to D. similis and M, calamogonus, the cecido
myiid (1) has a greater geographic range and (2) occurs on more Chionochloa
species; however, these trends might be due to poor sampling of D. similis
and M. calamogonus early in the season. The cecidomyiid appears to be less
easily satiated than D, similis by masting in Chionochloa.