Cordell:

I was wondering about the Baetis (Mayflies) on the Provo River and the Green River in Utah. I catch a lot of fish when the Baetis hatch. The fish seem to move up into faster water and start eating on the Baetis that are emerging, swimming, and floating on the surface. The question that I have is do you know why I stop catching fish when the hatch is over. Do you know if the insects just stop swimming, if the fish dont like to exert a lot of energy when nothing is hatching (water might be cold still) or maybe something else if happening?

A Mayfly

I am told, by a colleague of mine who is an avid fly fisherman, that you are probably fishing the wrong insect lifecycle or water column.

Mayflies have 4 main life stages (nymph, emerger, dun, and spinner) that are important to know for the fisherman. Nymphs spend their time under rocks and in the stream bed debris. Fish will feed on nymphs as they move from the rocks and drift down stream. This usually happens early morning to mid-day. Emerger is when the nymph begins to swim to the surface in order to molt before hatching into an adult. The dun, or adult mayfly, hatches and crawls on top of the water’s surface. Usually adult flight occurs mid-day during hatches and mating swarms take place. After mating takes place, the females fly back to the water to deposit eggs. Since adult mayflies only live for a day or two, the last life stage is also important for fishing and they are called spinners. Mayflies become weak after a full day of mating and laying eggs and they eventually fall to the water’s surface and die. Usually spinners are found at the end of the day, so as a fisherman, you’d change your style of fishing to match a spinner (meaning no drag on the line) if you were fishing in the evening. Knowing not only the insect’s life cycle, but also daily activity patterns in the stream/river is a useful tool for any fisherman.

So, to answer your question…you probably catch more fish during hatch because thats where all the activity is at that time, especially if your line is near the surface of the water. Both nymphs and fish are up and active at the surface of the water. After hatch is over, you’d want to switch your fishing technique so that you are fishing the lower water columns by the stream bed where all the next generation nymphs will be active and where the fish will be searching for meals.

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.

AdLand

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.

That snapping turtle is probably the largest one I have ever seen in the wild, had to be at least 15lbs.