Stinging and Injection Devices of Animals

Cases of convergent evolution

What qualifies as a sting and what had better be called a bite is not always clear and most people say they’ve been bitten by a mosquito while some refer to the “bite” as a “sting”. If the sharply pointed end of a structure is pushed into the tissue of another individual, I think we should call it a sting  –  and stinging animals abound. The stinging devices in animals are amazingly diverse and although we tend to think immediately of the defensive stings of bees and wasps, stinging is also used to deposit, for example in female parasitic wasps, their eggs into caterpillar or spider hosts on whose tissue the larval baby wasps can feed. Injecting venom can be the fastest way to immobilise prey and some stinging animals like, for example the fish-eating slowly moving cone shells or some spiders and snakes that inject venom into their victims, make use of their stinging devices in this way. To obtain oxygen under water without having to come up to the surface, the larvae of the mosquito Mansonia spp. impale the air-containing cavities in the stems of underwater plants with their syringe-like “stinging” syphons.

Venomous snakes, depending on the species, have two ways of delivering the venom to their victims. In those with venom glands connected with teeth at the back of the mouth, the teeth are not hollow, but possess a narrow groove on their inner side, in which the venom runs along. More dangerous are the hollow front teeth of some snakes. These teeth are normally folded up and tucked away under the roof of the mouth when not used, but when needed they point forward to strike the prey and to deliver the venom through tiny pores at their tips. The bite is carried out with a considerable force and the venom is forced from its storage glands into the wound of the victim. A rather similar method is employed by spiders, which also inject venom through a canal inside their two oral appendages, known as chelicerae. The chelicerae have very pointy tips with a hole at the end and the venom stems from the glands at the base of the chelicerae or from deeper in the head. How a droplet of the liquid venom can be pressed through the very narrow tube in the hollow chelicerae and then leave through the tiny pore at the end is something for scientists interested in fluid mechanics and involves some knowledge of the viscosity of the venomous liquid. In most web-building spiders the two chelicerae work like pincers, but in the often much bigger mygalomorph spiders the chelicerae work in parallel striking prey like 2 axes from above.

Similar fluid mechanical problems would apply to the venom delivery of wasp and bee stingers, for they resemble hypodermic needles. The honey bee stinger is barbed (a bit like that totally unrelated stinger of the stingray) and stays in the flesh of a stung human, leading to the death of the bee, but continues to pump venom by itself for some minutes. Wasp stingers and those of some powerfully venomous ants like the Australian bull ant are smooth and can be used repeatedly. Giant centipedes are feared because of their strong mandibles, sometimes referred to as ‘fangs’, which possess a canal through which a venom can be injected into a bitten individual. However, stingers delivering a potent venom that can kill are known not from centipedes, but scorpions. The most dangerous stinging animals in the sea are probably the already mentioned cone shells with their single hollow chitin tooth connected to a venom bulb, further the so-called stone fishes and some others with venomous fin rays as well as stingrays (the death of Steve Irwin comes to mind). The only “stinging mammal” is the male platypus with its venomous and hollow hind leg spurs. But who’d want to pet or even have a chance to pet a platypus?

© Dr V.B. Meyer-Rochow and, 2020.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content. 

Keep on Dreaming

But did Blondie and Aerosmith ever dream about insects?

I knew a Chinese girl who told me that she often dreamt about snakes and that the dreams frightened her. But I love to dream and my dreams never frighten me. It’s like entering a parallel world: you can be in unusual places, experience otherworldly adventures, solve scientific problems and, like Alice in Wonderland, meet strange creatures. The few dreams I’ve had in which insects appeared were pleasant ones, like finding a new and fantastic species of weevil with moss growing on its back or discovering an insect so small that one could hardly see it without a magnifying glass. And yet there are apparently people who encounter insects in their dreams that frighten them just like the snakes did in the dreams of my Chinese friend. I suggested to her that I could try to replace the snakes in her dream with ants or perhaps flies, but she did not like that idea.

By chance I came across a 2012 paper in the journal “Insects” by Barrett Klein, who wrote about people that had dreams about insects. Interpreting dreams that contain insects in them is a controversial issue and I guess the quotation by Barrett Klein attributed to James Horne that “Sometimes it can be difficult to say who is fantasizing more, the dreamer or the dream ‘interpreter’” is not too far off the mark. Often the interpretation depends on who dreamed what about the insect. Farmers, for example, dreaming about locusts are more likely to be worried about their crops and nasty people than others who will connect grasshoppers with a sense of freedom and enlightenment and fun.

When flies, fleas and lice occur in a dream anxieties, frustrations, fears and sorrow may be behind it, but dreams in which butterflies play a role are frequently linked to creative thinking, romantic encounters, and feelings of happiness. Dreams of bees and wasps are difficult to interpret as they could signify positive things like wealth, good luck and success and an ability to meet challenges , but also that trouble and dangers lie ahead and that fear and sickness may take over and that there are enemies to get to the dreamer. Unsurprisingly, beetles, representing the by far most species-rich order of insects, can, on the one hand, be part of pleasant dreams in which the beetles may be linked to success and positive images (ladybird beetles are so cute) or, on the other hand, may feature I dreams in which they are seen as harbingers of loss, death and destruction (carrion beetles and dung rollers perhaps).

It has been noted that the insect dreams of children aged between four and six years of age reflect the children’s  situation of being small and weak, basically powerless and it has been documented that insect and snake phobias were more prevalent in the female students’ than in the male students’ dreams, based on studies that had involved several Canadian universities. The great enthusiast of dream interpretations, Sigmund Freud, recounts and explains several cases in which psychological problems of people manifested themselves in their dreams containing a variety of insects.

Being well aware that (at least) mammals other than humans also dream as behavioural observations and encephalographic brain recordings have shown, one cannot help but think, if their dreams might not occasionally also feature insects. And going a step further one might even wonder if sleeping insects themselves not only dream, but would then have dreams about those annoying humans. 

© Dr V.B. Meyer-Rochow and, 2020.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content.

biology zoology blog benno meyer petioles

Petioles aren’t Petty at all

But what really are they then?

Petioles are not petitions and botanic petioles aren’t entomological petioles. So, what are they? Their etymology gives us a clue, for petiole comes from petiolous (= little foot, stalk). In entomology, however, it does not refer to a foot, but to the narrow waist characteristic of the bodies of wasps and all other members of the insect group known as Apocrita, i.e., the hornets, ants and bees. We are keeping wasps and hornets here in our laboratory in Korea, because farming wasps has become an industry in China and wasp larvae, which incidentally (just like the larvae of the other Apocrita) do not possess the petiole, are considered not only edible, but delicious in taste when lightly fried in oil.