Larvae of case-bearing leaf beetles protect themselves with hard cases made of fecal matter.
“Animals create a wide variety of structures to deal with and
challenges. We evaluated an intriguing structure whose function
has never been thoroughly tested. Specifically, we evaluated the
hypothesis that the body-enclosing ‘faecal case’ created and lived in by
the immature stages of Neochlamisus leaf beetles reduces their
risk of predation. We especially focus on the case of N. platani,
which is externally covered with host-plant trichomes, and includes a
distinct trichome-filled chamber (‘attic’) in the case apex. Here, we
separately evaluated the effects of case, trichomes and attic on each of
several behavioural stages of predator attack using N. platani
and N. bimaculatus larvae and pupae. Three generalist predators
(crickets, soldier bugs and lynx spiders) that represent different
feeding strategies were used in our individual-level repeated
observation behavioural trials. Results strongly demonstrated that the
faecal case itself greatly reduced predation risk for all combinations
of beetle species, life history stage and predator. Additional evidence
indicated that both trichomes and attics further and independently
reduced predation risk. Variation in results among treatments was also
informative. For example, the capacity of faecal case components to
reduce predation sometimes varied markedly among predators and between
larval versus pupal life stages. Patterns of predator behaviour provided
no evidence that caseless larvae have alternative means of defence.
This study further presents a rare example of the co-option of a
physical plant defence (trichomes) by an herbivore.” (Brown & Funk 2010:127)
“As excrement goes, the beetles produce remarkable stuff, Funk says.
Despite weeks of wear, it stays firm and fungal-free. To a human nose it
doesn’t smell and, after some complicated moments trying to collect
larvae, Funk can add that it doesn’t have a discernible taste either.” (Milius 2009)
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-4XMC05H-2&_user=10&_coverDate=01%2F31%2F2010&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1330158264&_rerunOrigin=scholar.
