|Convergent Lady Beetle (Hippodamia convergens)|
on Kitt Peak, Pima Co, AZ in June
|Nymphs of the Giant Mesquite Bug (Thasus neocalifornicus)|
Nymphs of the Giant Mesquite Bug (Thasus neocalifornicus) enhance the effectiveness of their aposematic pattern and coloring by staying together with 'litter mates' until they are grown. Their deterrent is a row of acid producing glands on their backs.
|Aztec Spur-throat (Aidemona azteca) nymph|
|Aztec Spur-throat (Aidemona azteca) adult|
We have a grasshopper in AZ that may be an example, but I cannot find any research papers about it. But take a look at the young Aztec Spur-throat (Aidemona azteca) on the left and compare it to the adult. The nymphs feed on Datura in my photos. I have not seen the adults feed.
|Taeniopoda eques (Horse Lubber) female|
Our horse lubber shows yellow patterns on black, and when really threatened flash their red hind wings in addition. Are these grasshoppers toxic? Or just using a startle tactic on a predator? I often see them cannibalizing corpses of their own kind. But: I kept a ground beetle in a terrarium. I had found the beetle feeding on a dead Plains Lubber. When I offered a dead Horse Lubber the beetle seemed ready to rather starve than eat that one.
|Eleodes sp., Stink Beetle, Pinacate Beetle|
The only purpose of warning colors targeting potential predators is to be impressive, recognizable and memorable.
Not all aposematic colorations are geared towards day-active, color-seeing birds, lizards or humans. Many insects are most active during dusk and dawn, the time when 'all cats are gray', meaning that colors become rather invisible. The crepuscular Pinacate or Stink Beetle is solid black. But its habitat has lots of open space with light colored sand. So its black shape stands out very well. The beetle adds an aposematic behavioral signal by standing on its head when threatened. This also allows the content of two big glands that eject at its rear to run down over its whole body. And the collector's hands. The signal of 'big black beetle walking intermittently and tending to stand on its head' is so successful that it is imitated by several non-smelly darkling beetles, a very smelly, but rarer ground beetle, and by big black, flight-less, harmless Cactus Longhorns.
|Yellow Jackets and other Vespidae|
|Iron Cross Beetles Tegrodera aloga|
A very impressive blister beetles, it seems to be clearly advertising that it is loaded with cantharidin. Horse owners are often alarmed when they see these beetles. But the Ironcross beetle is big and obvious and does not live in meadows where hay is grown. It's the smaller striped Epicauta sp. that sometimes get caught in great numbers in Alfalfa bails and can cause severe poisoning in horses. Harvesting methods that don't allow the beetles to escape are partly to blame.
Tylosis maculatus, a longhorn beetle (Cerambycidae)
Yavapai County, AZ, July
The beetle lives on Mallows with mostly orange flowers, so the coloration could also be cryptic. But Mallows are also full of phytotoxins, some used in herbal medicine, some outright poisonous to grazing cattle (central nervous system). So the beetles may sequester those chemicals to become impalatable.
|Tetraopes spp., the four-eyed milkweed longhorns|
One of my beetle collages photographed from living specimens
Quoting EOL: The lycids, or net-winged beetles, are soft-bodied beetles, presenting aposematic colors and high levels of toxins, known as center models in mimetic rings (Marshall and Poulton 1902; Shelford 1902; Guenther 1931; Darlington 1938; Linsley et al. 1961; Moore and Brown 1981). BTW, their close relatives, the fireflies, are just as toxic. Many keepers of lizards found this out. Inexperienced tropical lizards will ingest them and die!
Lycids often aggregate in great numbers to mate. In Madera Canyon you can find them swarming around oaks, and in the desert a different species often covers certain blooming mesquite trees. As the neighboring trees usually have no visitors at all, I assume that clouds of pheromones are bringing the beetles together.
The Tarantula Hawks, a common name that describes several Pompilid species in the genera Pepsis and Hemipepsis, carries the most painful sting in Justin Schmidt's book. So it's not surprising that this wasp comes with a warning. Or does it? The top one is a Hemipepsis (I think) with orange wings. The next one is a Pepsis grossa, but this is the all black version. Others in the same species have orange wings and the 2 morphs mate and live in the same areas. The third one is a Sphecid, Sphex tepanecus. It's as big as a small tarantula hawk and might also sting, that's why I have included it here. The last one is the Robber Fly Wyliea mydas. It has no sting but a very painful bite. So these huge orange-winged, black-bodied insects are all able to defend themselves. Giving the same kind of warning, they enhance each others effectiveness: Muellerian mimicry. There are many harmless species that also mimic these, but that will be the theme for another week.
|Automeris cecrops pamina|
In this group, we already had a Queen caterpillar that is toxic because its host, milkweed, is full of toxins. Its aposematic colors warn predators not to eat it.
The Io moth caterpillar in this image can inflict harm simply through skin contact, ad it advertises that danger with lively patterns and colors.
'As is true of most species in the Hemileucinae, the caterpillars of this species can produce a nettle-like sting from their spines. Some people show little or no reaction, while others may develop an itchy rash or welts that last for up to a few days, especially on areas of more tender skin. These caterpillars are not considered dangerous, but should be handled with care.' BugGuide info page