Tuesday, April 26, 2011

Paracotalpa ursina

Unofficially this attractive beetle has been called the little bear beetle. Officially it is Paracotalpa ursina - which literally means the little bear Paracotalpa. And the bear is easy enough to imagine with the long setae (hair) and the plump body. The beetle belongs to the family Scarabaeidae - notice the fan-like antennae. It is a bit over half an inch long but seems bigger, especially as it climbs up grass stems and topples them over with its weight.

Jon and Michael found a population of the beetles last week in a city park here in Fresno and I went out yesterday to see them myself. There is something about a scarab in flight - with its elevated wing covers, low buzzing and erratic flight - that gets my beetle juices flowing. Museum specimens of this insect tend to be dull reddish brown. Live specimens have a much deeper red color. They're a sight to behold. Sadly, there were several along the park trail that had been smashed.

The place where the beetles were flying is not all that remarkable. It's maybe a quarter of a mile from the San Joaquin River and is just a fenced-off area with tall grass and a few other plant species. But that's often how you find interesting insects. They don't always live in the places we would consider ideal. And a grassy path in a park seems to be just fine for these brightly colored bruins.

Wednesday, April 20, 2011

Eleodes gigantea

Eleodes gigantea is a big black darkling beetle common throughout California in dry areas. It gets to be about an inch long and is really the epitome of the so-called "stink beetle". There are several species of Eleodes throughout the Western US and Mexico but E. gigantea is certainly one of the biggest. It is also one of the most - how should I describe it - expressive. Once it gets bothered, it sticks its rear end into the air, threatening to give off a foul odor, if anybody gets too close.

Last November, Michael decided he wanted to do a science fair project on these insects. He wanted to see if they had evolved their defense response as a protection more from aerial predators than from terrestrial ones. He made silhouettes of a predatory bird and another one the same size of a fox. Then Michael, Jon and I took a trip out past Coalinga (southwest of Fresno) to find the creatures. We spent 2 days driving around mountain roads and ended up finding several individuals that Michael exposed to the two silhouettes.

Michael thought that the beetles would go into defensive mode quicker when exposed to the fox. After all there are a lot of terestrial predators around - including a lot of non-native cats and dogs. But the beetles were much quicker to respond to the bird. It was a fun project and leaves open a lot of questions that somebody doing more than a high school science fair project might want to tackle.

In any event, the canyon was nice. Not too many insects were out (it was November) but the cool weather didn't seem to bother the beetles.

Friday, April 8, 2011

Hypera brunneipennis

This time of year alfalfa can really be hit hard by weevils. Here in the Central Valley we have to deal with the Egyptian alfalfa weevil (Hypera brunneipennis). These pictures are from about a week ago on a plot that has had a heavy infestation the last few years. As you can see the feeding damage can be significant.This first picture is of a mature larva - the stage that does most of the damage. Smaller larvae don't eat nearly as much as the larger ones. This particular individual is about a quarter of an inch long.

It surprises me how much of a problem these weevils have become. They are really not that hard to control if you disrupt their life cycle with an early cutting. This only needs to be done once (on the year's first growth) because the insect only goes through a single generation a year. Here in the Central Valley, a cutting around the middle of March would kill most of the population. A good pyrethroid will do a good job too if you decide to wait and make the first cutting with a more mature crop.

The Second picture is of the cocoon. When the larva gets as big as it is going to get, it will find a secluded place on the plant (sometimes on the ground) and encircle itself with a silky protective covering. You can see that it isn't as tightly constructed as the cocoons of other insects but it does the job at keeping most predators and parasitoids away.

This last picture is the mature adult - no doubt out looking for a mate