are found on 83.3% of the fertile palms and on 4.0% of the sterile palms. Bug density is about 137 times higher on the former than on the latter. On fertile palms, 47.0% of the bugs are adults, of which 83.5%, as well as 93.5% of the nymphs, are on reproductive structures. The only 3 bugs found on the sterile palms were females. Sex ratio on fertile palms is about 1 male for 6 females ; no males have been captured during the rainy season. Eggs were present on inflorescence peduncle during the transition from dry to rainy season.
TABLE II Population size and structure on Lincus spurcus and L. malevolus on Amazonian native palms (n : number of bugs; F : frequency of palms with bugs (%); N : palm sample size ; m : mean density per palm with bugs; M :
mean density calculated per palm, from N).
eegs nymphs females males n F N m M
A — L. spurcus on Astrocaryum sp. aff. A. murumuru (data cumulated from April 1988 to February 1989) :
B — L. malevolus on Astrocaryum macrocalyx (data cumulated from January 1988 to April 1989) :
sterile palms 0 1 21 1 23 9.8 34 5.8 0.7
fertile palms 4 53 68 2 123 88.9 9 15.4 13.7
leaves 0 23 68 1 92 13.1 10.2
flowers 4 6 0 0 6 3.0 0.7
fruits 0 24 0 1 25 6.3 2.8
C — L. malevolus on Astrocaryum sp. (data cumulated from June 1988 to March 1989) :
sterile palms 0 0 10 1 14.3 7 1.0 0.1
fertile palms 11 73 69 14 156 66.7 9 26.0 17.3
leaves 6 32 61 14 107 17.8 11.9
flowers — — — — — — —
fruits 5 41 8 0 49 8.2 5.4
D — L. malevolus on Elaeis oleifera (data cumulated from June 1988 to April 1989) :
sterile palms 0 0 3 0 3 4.1 47 1.5 0.1
fertile palms 3 123 94 15 232 89.3 28 9.3 8.3
leaves 0 8 15 3 26 2.6 0.9
flowers 3 50 36 8 94 7.8 3.4
fruits 0 65 43 4 112 11.2 4.0
DISCUSSION
Lincus spurcus and L. malevolus are present and form dense populations on native Amazonian palms, Astrocaryum sp. aff. A. murumuru for the former, A. macrocalyx, A. sp., and Elaeis oleifera for the latter.
The differences in the spatial distribution of bugs in the palm may be related to the abundant, flattened, black spines and the leaf sheath fibers of Astrocaryum spp., which are absent in E. oleifera. These spines allow the bug to hide, and avoid it from falling to the bottom of the leaf sheath where it can be crushed by the wind induced movements, or drowned in the water accumulated after rainfall. They also accumulate lots of litter, under which these bugs are often hidden, as first pointed out, for Lincus sp., by Louise et al. (1983).
The adults are likely to be attracted by the aromatic volatile compounds of the inflo- rescences, new palms being colonized as a result. We never managed to capture the spe- cies of Lincus by light trap ; they are photophobic and probably move by night flight.
The two bug species of Lincus spp. differ by their reproductive strategy, as shown 252
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