Watering the Plants leads to Rare Beetle Discovery - Observation of the Week, 2/20/24

Our Observation of the Week is the first Megamerus alvarengai leaf beetle posted to iNaturalist! Seen in Brazil by @alenilson.

“As a child I had a lot of contact with nature through my grandmother, who was a farmer,” recalls Alenilson Rodrigues. 

I sometimes accompanied her in her efforts in the field and that's where my passion came from. As time went by I started going to the forests as a way to de-stress and I started taking photographs at the suggestion of my wife. At that moment I was having personal problems that were distracting me and photography came to me as a way to change the direction of my life. Without a shadow of a doubt my wife always deserves to be highlighted for my photography. If it weren't for her suggestion we wouldn't have these images today.

I developed a special taste for photographing arthropods, especially flies and moths, and I ended up developing a technique that generates images with a white background, giving me the nickname “studio macro”. It's a very laborious method because I only register live animals and after registration I release them in a safe place, most of which I find on my property or nearby.

He came across this Megamerus alvarengai beetle while at home, and at first didn’t know it was a particularly special find. 

There is no great story, I simply believe that any living being should be photographed so that there is the possibility of knowing its occurrence as well as a means of protecting it, as I believe that only what is known is respected. While watering some plants I noticed the beetle hidden among the leaves and registered it. It was @borisb who identified both the being and its importance.

Boris Büche (@borisb) is iNaturalist’s top identifier of beetles, having added IDs to over 650k (!) verifiable observations of them, so I reached out to him about Alenilson’s find to get his thoughts on it. He says that the subfamily to which it belongs (Sagrinae) is an ancient branch of leaf beetle evolution. Most extant members of it are found in the old world.

When I saw the discovery by @alenilson, my first belief was that it would be something completely unknown. I remember well my identification of Atalasis sagroides four years ago, then found to be the single American representative in the basic checklist by Blackwelder (1945/46).

M. alvarengai was discovered five years afterwards in the state of Rio Grande do Norte, Brazil (seven examples, found by Moacyr Alvarenga in 1950, scientific description in 1956 by Francisco de Asis Monrós). The beetle was found again only in 2009-2013 during a trap sampling campaign in Caatinga formations in the state of Paraíba (twenty examples, in xerophilous vegetation) - and now, by Alenilson.

Alenilson found two of these beetles (here’s the other), and both were on coconut palms, but Boris thinks it’s likely not their host plant. Not much is known about the species, but host plants for other members of the subfamily are dicots, not monocots. 

Larvae of its Malagasy relatives form galls (unpublished observation), and pupae of two Australian forms (including a Megamerus) have been found within earthen cocoons underground. One iNaturalist observation of a female laying eggs would support the suspicion that larvae of Megamerus are root miners.

“I use iNaturalist to promote the animals I find in my region,” says Alenilson (above). 

Here I can meet experts as well as see  the occurrence of different animals in different points of interest. After getting to know the platform I discovered people and places, and of course, several animals that occur here in the state along with other people who share the same interest.

(Some quotes have been lightly edited for clarity and flow.)

- you can follow Alenilson on Instagram and YouTube!

- this observation is the First Known Photographs of Living Specimens project!

Posted on February 21, 2024 05:13 AM by tiwane