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Excerpts from Jim Conrad's
Naturalist Newsletter
from the November 15, 2015 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins,
central Yucatán, MÉXICO
CACTUS BUG
About four years ago I planted a pad of Nopal Cactus -- a spineless, edible species much
cherished by Mexican country folk who eat its pads and fruits -- in front of the hut. Now
the cactus consists of many pads and stands higher than my head. One morning this week I
noticed some bugs on it apparently making themselves at home, which included feeding on
the cactus and procreating on it, as shown above.
A close-up showing a prettily stripe-faced one with his slender, strawlike proboscis inserted into a pad is shown below:
In calling this species a bug I'm using the term "bug" advisedly, because these critters are members of the insect order Hemiptera, known as "true bugs." Technically, ladybird beetles aren't bugs, because they're beetles. But these bugs on my Nopal, with their distinctive sucking mouthparts and four wings, with the front wings thickened at their bases, are classic bugs, technically correct bugs, in fact "true bugs." As a kid on the Kentucky farm, the best-known true bugs were "stinkbugs," whose shapes were very similar to these, and who stank defensively if poked at too roughly.
But these cactus-living bugs outside my hut door aren't stinkers. Still, the world of True Bugs is so enormous and diverse that just about any kind of behavior can be expected of one or another of its species, not just stinkiness.
I was especially interested in these bugs' identity because during my recent stay in Río Lagartos the tops of fenceposts throughout the surrounding country often were affixed with yellow, harmonica-size items the shapes of prisms, their ends open and their interior walls coated with flypaper-stickiness, and pheromones. The pheromones attracted a certain kind of insect whose hungry larvae threaten to destroy many of Mexico's Nopal Cactus plantations. We don't have big Nopal plantations in the Yucatan, but in the dry uplands of central and northern Mexico they do. The pheromone traps were monitored regularly to watch for the destructive bug's appearance here. Therefore, could these bugs on the cactus outside my hut possibly be one of them? The pictures were sent off to volunteer identifier Bea in Ontario, who with her usual expertise quickly replied that they were LEPTOGLOSSUS SUBAURATUS.
It turns out that Leptoglossus is a diverse and complex genus, with 61 species recognized in the Americas. Since true bugs sometimes are of importance to agriculture, they're better studied than some other orders, and it was possible to download Harry Brailovsky's 2014 work in the journal Zootaxa, the title of which begins -- in case you want to Google it -- "Illustrated key for identification of the species included in the genus Leptoglossus... "
The Internet is peppered with lists showing that Leptoglossus subauratus has been collected here and there in places from southern Mexico to Costa Rica, and a few notes detail such matters as the species' tibia length and the color of its pronotal disk, but there's hardly any information out there describing the bug's behavior, except for one note that a collection was made on a cactus. Apparently Leptoglossus subauratus isn't the bug decimating some of Mexico's cactus plantations, else surely it would be mentioned somewhere.
So maybe our entry here will help a graduate student someday by letting them know that here in the Yucatan in mid November, Leptoglossus subauratus can be found feeding and mating on Nopal Cactus, Opuntia ficus-indica.
the January 10, 2016 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins,
central Yucatán, MÉXICO
CACTUS BUG NYMPHS
Now the results of last November's orgiastic period are in evidence, as shown below:
That photo shows three things worth noting.
First, down in the lower, left corner an adult Cactus Bug seems to be hovering in the vicinity of the brood, though normally we don't think of bugs as watching over their offspring. The next day the adult still was nearby. The third day I couldn't find the adult. On the fourth day the adult had returned but was about a foot away on a different part of the cactus.
Second, the face of this cactus pad is strangely wrinkled, though other pads in the area aren't. Does this reflect internal damage to the pad resulting from the Cactus Bugs' presence?
Finally, there's the offspring themselves, which are "nymphs." Nymphs are the young of insects who undergo simple or incomplete metamorphosis. In complete metamorphosis you have egg > larva > pupa > adult. In simple, you get egg > nymph > adult. Nymphs are basically smaller versions of adults, but with wings and sexual parts only partly or not at all developed. Below, a closer look at some nymphs is provided:
Notice how closely individuals in the cluster position themselves to others, some bugs even climbing atop others. Also, individuals on the cluster's perimeter mostly face outward. Probably they cluster in order to provide a more vivid splotch of red on the green cactus pad, the idea being that often dangerous animals announce themselves with bright colors and patterns, so predators are warned to stay away. However, I find nothing dangerous about these bugs. Lots of species bluff -- like milksnakes which bear red and black bands like venomous coral snakes, though they're harmless.
In the above picture, the variation in size and pattern is striking, It looks as if individuals of different ages live in the group.
I'm documenting these details because earlier we saw that this species is poorly known. Someday someone will be happy to have this information as a starting point for their own studies.
the February 7, 2016 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins,
central Yucatán, MÉXICO
METAMORPHOSING CACTUS BUGS
This week most of the nymphs introduced above metamorphosed into adults. Below, you can
see a whitish one with pink highlights almost finished emerging from its blackish husk:
Below, another shot of one whose emergence is less advanced than the one's above reveals how during emergence the head is bent tightly against the abdomen's bottom:
The pictures are shown out of sequence because that last one can be hard to interpret if you don't know what you're looking for. When I first saw an emerging nymph in this stage I thought it was headless, and saw the head only once the picture was on the laptop screen.
Freshly minted adults remain whitish for several hours but by the next day they display the adults' typical colors, shown below:
In that photo recently emerged adults stand next to nymphs that are far from reaching the instar stage at which they also will become adults. We noted earlier that clusters on the hut cactus contained nymphs of various age groups.
Compared to now last week maybe three times the number of nymphs could be found on the cactus, in two or three groups, but something happened to most of them. I noticed this after a particularly chilly night with intermittent sprinkles, but don't know whether there was a connection.
Sometimes when I put my face up close to the cluster one or two larger nymphs raise their rear ends and squirt out drops of fluid. Maybe they do this all the time, or maybe they're doing it just for my benefit.