Dave

I’m wondering if there’s any way of knowing how many images a compound-eyed insect receives. (I’m reminded of the Far Side cartoon in which “the last thing a bug ever sees” is an entire panel of the same image, broken into tessellating diamonds: a woman holding a fly swatter.)

I’m very curious. Please answer using layman-speak, if there is an answer.

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Insects’ compound eyes, in general, bulge out on either side of their head. This increases their field of vision on practically all directions. I think I read or heard somewhere that water boatman (an aquatic beetle) can see something like 245 degrees in the horizontal plane and 360 degrees in the vertical plane. The classic theory on insect vision is called the mosaic theory and it suggests that each cell (ommatidia) forms an image of the limited part of the visual field. So, in layman speak, each cell puts together a part of the picture to form the entire object.

You can see a previous post on the insect eye if you want a little more info.

Mohamed:

Do you have pictures of insects malformed by insect growth regulator insecticides?

Inu:

what is most effective as a biological control, predator or parasitoid, why?

I personally don’t have any pictures of malformed insects due to an insect growth regulator. Sorry. But honestly, I don’t know how ‘malformed’ the insect would be. The way the growth regulator insecticides work is by preventing the insect from reaching adulthood. Some of the most common insect growth regulators are methoprene and lufeneron which are used for treating mosquitoes and fleas, respectively. Methoprene is a hormonal analogue of juvenile hormone (JH). It prevents the insect from molting into an adult and the larva/pupa eventually dies. Methoprene is used in water storage tanks to control mosquitoes. Lufeneron, which is a tablet you feed to your pet to control fleas is a chitinase inhibitor. Flea larvae have a chitin tooth that they use to break out of the egg and the chitinase inhibitor causes the tooth to fail to develop. So, the larva cannot hatch from the egg and dies.

What is more effective as a biological control, predators or parasitoids? Gosh, good question but I think the answer would vary depending on the person you ask and which predators/parasitoids you had in mind because there are pros and cons to each. Natural enemies (predators, parasitoids, pathogens) are biological control agents. There are several factors that render a biocontrol agent as effective and include things like (a) narrow host ranges, (b) habitat adaptability, (c) synchrony with the host life cycle, and (d) high reproductive potential. In my opinion, I would argue that parasitoids fit some of these factors more readily than predators would. And most predators tend to be generalists and would also effect non-target groups. But again, depends on who you ask.

Shakell:

What are the stages of a longhorn beetle life and how long do they live?

I can’t speak about all longhorn beetles, but the more famous wood boring kind (like the one in the picture above, which is a pine sawyer) start out as an egg in the tree. The adult female chews a hole in the tree and then turns around and deposits the eggs inside. The eggs hatches and the larva develops through several instars (a stage in between molts). Then the larva goes into a pupal stage and eventually reaches adulthood and chews its way out of the tree.

How long they live for depends on a lot of things…like food source, predation, in the wild vs. the lab, which species. I would say as generally speaking that they could live for several weeks.

Lisa:

I have ants in my house that (A) I can’t get rid of, they almost laugh at those litle plastic traps, and (B) when I smush them, I smell this cleaner smell. Why is that? I noticed it when squished one kind of close and thought I was crazy so the 3rd time I just smelled the dead ant and it was pretty potent. I know this sounds weird but my husband thought I was crazy when I told him what I smelled. So I smelled it. What is it that makes them smell like that?

Getting rid of ants can be tricky. Ants communicate using three main methods, (a) tactile, (b) auditory, and (c) olfactory. Ants use pheromones and odors to identify fellow members of the colony and to identify trails to and from the nest. If your plastic traps are not in the right areas they could be less effective in attracting the ants to them. I actually have never used those plastic traps, but instead have tried to identify the main pathways or trails the ants are using (especially if there are points of entry into your house) and have lined a wall of dish soap along the path. Ok, so actually I have 2 ant stories where I have used soap. One was in an apt and I noticed the ants coming through a crack between the door and kitchen and they were coming up to the kitchen sink for whatever they could get of leftovers. So, I put a line of the soap on the ground by the door (like a baracade) and lined the side of the sink with dish soap. At the end of the day when I cleaned up the kitchen I washed the sink area up, usually having to clean up dead ant bodies, and then would repeat with the soap treatment the next day. I only had to do this for a couple days before the ants got the hint and left. Now if the colony is actually nesting in your home (like carpenter ants) then you would have a much bigger problem on your hands and may have to call an exterminator. It might help to identify what kind of ants you have in order to best combat them. The second time I battled ants was while in grad school, during winter. A bunch of crazy ants got the crazy idea to invade my blow fly colony and steal their sugar water. In the process they also killed many-a-fly…and that was no good for someone who was using those flies for experiments. Unfortunately I couldn’t find any main trail, they were everywhere, literally in the thousands. So in this case I filled a spray bottle with soap and water and sprayed the ants that were outside of the blow fly cage and just put a line of soap around the outside of the cage to prevent new ones from going in. After a couple of days of spraying soap water around the floor and cabinets of the lab and killing the ants I could see they finally went away.

For the second part of your question about the smell, well, you are not crazy. Ants belong to the insect family “Formicidae”. That odor you smell is a chemical from their poison gland called formic acid. Formic acid smells like vinegar, I think, its been a while since I have smelled a crushed ant. Its also the same chemical in stinging nettle, if you have ever come into contact with that plant. Ants use the chemical for defence against other ants and predators.

Good luck

Patti:

I am preparing slides for an exhibit and was hoping to do a dragonfly eye can you tell me the process of dissecting the eye?

Hmm, can’t say that I have ever removed a dragonfly eye before. I have, however, removed a blow fly’s eye before and it is definitely a little messy.

First of all, you have to know a little something about an insect’s eye. Insects have compound eyes that are made up of units called ommatidia. I haven’t personally counted, but it is said that some dragonflies can have as many as 10,000 ommatidia. An ommatidium is a bundle of cells that contains the corneal lens and crystalline cone. Next to the cone are the retinular cells, which are in turn arranged around the rhabdom (the axial structure)…together, the retinular cells and rhabdom are called the retinula. Why is dissecting the eye messy? Because surrounding the retinula is a sheath of pigment cells. Each cell is full of red, yellow or brown granules of pigment. Rupturing these pigment cells while trying to remove the eye is what causes it to be messy. Next, axons of the retinula enter into the optic lobes of the brain.

I think in order to get the cleanest dissection, or removal of the eye, you would want to pick open (with forceps) and remove the cuticle of the head capsule away from the compound eye…and ideally, you would want to expose the brain, gentlly pull apart the optic lobe from the brain, and then use a forcep to gently grasp the entire compound eye + optic lobe. You may even want to just try pulling the eye away from the head capsule just by the optic lobe. Don’t try to pull at the compound eye from directly on with the forcep because you will more than likely rupture those pigment cells.

So with all of that, some of you may be wondering how they actually see? All those ommatidia…are they seeing thousands of the same picture? No. Johannes Muller in 1826 and Sigmund Exner in 1891 developed the classic theory on how insects form images, called the ‘mosaic theory of insect vision’. Basically, each ommatidium is sensitive to light that enters at a small angle. As light enters the ommatidia a dot-like pattern is formed. The entire image of what the insect sees is contructed from a ‘mosaic’ of information that is relayed from each ommatidia.

Let me know how the dissection goes

Many:

Would you please tell me about the camera and lenses that you use to take all of your amazing pictures? I am looking to buy a digital SLR that is capable of both macro and telephoto photography - any advice would be greatly appreciated.

The camera I use is a Canon Powershot S2 1S (6.0-72.0mm). For what it is, I like the maco capabilities. The telephoto ability on the other hand is not so great, at least in my opinion. I have bought a couple of the lenses that are available for the camera but haven’t had much luck with using them.

I can’t give a whole lot of advice on what kind of digital SLR to buy because I haven’t done a whole lot of looking into it…aside from just knowing I want to upgrade

There are several people though that could give you advice that read this blog…so hopefully they will chime in.

Hint hint…

Pat:

We collected a black beetle that is 3.2 cm long and 1.5 cm in maxium width. It is lens shaped in the top view and its ends are pointed, especially the rear. It was found on a tennis court in Pleasant Hill, Ca.

Photo credit: Pat V.B.

You must live by water because your little beetle friend is a predaceous diving beetle. They eat other aquatic insects and even small fish. What’s cool about these guys is that in order to breath they form an air bubble at their rear underneath the tips of their wings (elytra).

Cool find

Mike:

I live in the Rocky Mountains near Loveland, Colorado. I seem to be getting 2 to 3 Western Conifer Seed bugs in my house every day. The “stink” is pretty potent. I have tried everything I know to seal up all cracks and spaces in my log home. I haven’t done anything with my chimney. What else can I do? Thanks, Mike

Picture courtesy of Cornell Cooperative Extention

Unfortunately all you can do to keep these guys out of your house is seal up cracks and gaps around your house. There are no pesticides (not that I would reccommend that anyway) registered for these bugs. You could try screening your chimney. Otherwise it sounds like you are already doing everything that I would have suggested. If it gives you any more peace of mind, they are not harmful or anything

Maybe another reader has some clever suggestions?