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Psyche 
[Vol. 87 
identified as occasionally present in the spray. Neither was detected 
with consistency or in substantial amounts in extracts of the gland, 
but they were always present in extracts of the hindgut. Their occur- 
ence in the spray may be a further indication that rectal contents are 
sometimes ejected with the secretion. 
Laboratory tests done with formicine ants (Formica exsectoides ) 
and Swainson’s thrushes (Catharus ustulatus) demonstrated that 
Necrodes is well protected against such predators. The tests with 
Formica involved presenting individual tethered Necrodes to groups 
of 10 ants in small glass enclosures. The ants attacked immediately, 
by clamping onto the beetles with their mandibles, in response to 
which the beetles revolved their abdominal tip and sprayed. As was 
particularly clear from the patterns of droplets sometimes visible on 
the bottom of the enclosures, the discharges were accurately aimed 
toward the ants. These usually released their hold quickly and fled. 
At varying intervals thereafter they engaged in intensive cleansing 
activities, which seemed all the more protracted when the ants had 
been heavily contaminated with spray. Five beetles were exposed to 
ants in this fashion for 30 min. each. None received noticeable 
injury. 
The tests with the thrushes followed a protocol previously used 
with these birds in experiments with other chemically protected 
insects (Eisner et al., 1978). Necrodes were offered together with 
mealworms (larvae of Tenebrio molitor, which served as edible con- 
trols) to 3 individually caged birds (all males), in 3 daily feeding 
sessions per bird. Mealworms outnumbered Necrodes 2 to 1. The 
insects were offered one at a time, up to a total of 14-15 per session. 
Sequence of presentation was such that each series of 3 consecutive 
items consisted of two mealworms and one randomly placed 
Necrodes. Each item was left with a bird until it was eaten, or for a 
maximum of 2 min. Fate of prey was scored as follows: eaten ( E , if 
the insect was ingested after having been pecked no more than 3 
times); eaten with hesitation {EH, if the insect was eaten after having 
been pecked more than 3 times); rejected ( R , if the insect was 
ignored after having been pecked one or more times); not touched 
{NT, if the insect was not contacted by the bird during the 2 min. of 
presentation). Insects not touched at the end of a feeding session 
were not tallied, since such avoidance might have been due to satia- 
tion of the bird. 
