INSECTS ASSOCIATED WITH THE FLOWERS OF 
TWO SPECIES OF MALACOTHRIX (ASTERACEAE) 
ON SAN MIGUEL ISLAND, CALIFORNIA 
By Scott E. Miller 1 and W. S. Davis 2 
The insects associated with Malacothrix incana (Nutt.) T. & G. 
and M. implicata Eastwood on San Miguel Island were sampled as 
part of a general analysis of hybridization between the two species 
on the island (Davis and Philbrick, 1986). On San Miguel Island, 
M. incana is widely distributed on unstabilized and stabilized sand 
dunes on slopes near the ocean or on sandy substrate on the upper 
surfaces of the island including the slopes of San Miguel Peak and 
Green Mountain. In contrast, M. implicata is generally restricted to 
the slopes near the ocean or the walls of canyons above the ocean. 
Hybrid plants were found only where M. incana and M. implicata 
were growing in a common area and constituted less than 1% of the 
total number of the three forms in these areas. Hybrid plants were 
most frequent on the slopes above Cuyler Harbor and above Tyler 
Bight. 
Plants of M. implicata are spreading or erect perennials with large 
heads containing up to 80 florets. The ligules are white and have a 
purple stripe on the abaxial surface. Plants of M. incana are peren- 
nial and become mound-shaped after several years of growth. The 
large heads contain up to 100 florets with yellow ligules. The hybrid 
is also perennial and has large heads with pale yellow florets whose 
ligules often bear a reddish stripe on the abaxial surface. 
During our visit to San Miguel Island in May, 1984 a majority of 
the plants of M. incana , M. implicata and the hybrid were in full 
bloom. Numerous open heads were present on plants of both species 
and one plant of M. incana had over 200 open heads. Herbarium 
label data indicate that the blooming period of M. incana generally 
coincides with that of M. implicata on other Channel Islands as well 
as on San Miguel Island and that flowering of both species reaches a 
maximum in the months of May and June. 
'Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 
02138 and Dept, of Entomology, Smithsonian Institution, Washington, DC 20560. 
department of Biology, University of Louisville, Louisville, Kentucky 40292. 
Manuscript received by the editor October 16, 1985. 
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