1983] 
Douglas — Defense of bracken fern 
317 
until they are driven off or killed by the patrolling ant(s). Corpses 
are removed and taken down to the nest. Patrolling predaceous ants 
thus obtain both a nutrient-rich secretion in addition to arthropod 
prey attracted directly to the plant tissues or to the nectaries. The 
result is that the croziers are protected (to an unknown extent) from 
adapted and nonadapted herbivores during this most susceptible 
stage of growth). 
Species of smaller ants such as Tapinoma sessile (Say), Lepto- 
t borax curvispinosus Mayr, Leptothorax muscorum (Ny lander) and 
Lasius alienus (Foerster) engorge at the nectaries as well, but often 
in non-aggressive interspecific groups. However, none of these spe- 
cies appears to defend the bracken croziers from other arthropods, 
and thus they may be “parasitic” in the broad sense of the concept 
since the ants obviously benefit by gathering nectar, but the bracken 
potentially suffers because it loses its attraction to more aggres- 
sively-defensive ants. Although we have not documented any defen- 
sive role by these small ants in Michigan, it is possible that they 
remove the eggs of herbivores (Susan Koptur, pers. comm.). 
The immatures of at least 10 species of spiders also imbibe at or 
are attracted to the axillary nectaries, while several others are inti- 
mately associated with the unfurling pinnae. For example, when the 
immatures of Enoplognatha ovata (Clerck) bind the 3 pinnae 
together, the nectaries become effective “baits” within the pyramidal 
web, ensnaring many smaller nonassociated dipterans and parasitic 
ants. Other spiders such as the thomisid Tibellus sp. extend their 
body against the rachis, cepthalothorax pointing towards the nec- 
tary, and ambush other arthropods as they arrive to extract nectar. 
Finally, several species of salticid spiders (e.g. Metaphiddipus pro- 
tervus Walckenaer), prowl the developing bracken canopy, leaping 
from pinna to pinna in search of prey. Encounters between spiders 
and patrolling ants are not uncommon, but it is not certain which 
factors predispose one or the other to dominate a given frond. How- 
ever, the small parasitic ants are common prey items of the patrol- 
ling spiders in Michigan. 
By the second week of June, the pinnae have completely opened, 
and the nectaries darken and desiccate. Even so, patrolling ants 
continue to defend the mature plants for a few more days, perhaps 
attracted to the lingering odor of the nectaries. But the ant patrols 
are erratic and the ants stay on the plants for far shorter periods. 
