Urban Wildlife Guide

 

A couple of weeks ago I was in these mountains around Centralia, PA. I was hunting for plant fossils on a big patch of exposed shale; I'll be showing off the fossils I found in an upcoming blog soon. Among many pleasant sights of the day, this...

It was buzzing around ostentatiously, making noise, and flying near me. I thought it was an aggressive wasp at first because of the bright yellow and black stripes. It flew away before I got a better look. Only after seeing the photo did I realize it was a big fly. It's a hover fly or flower fly -- a harmless wasp mimic. It's common name is the Yellowjacket Hover Fly. Click to enlarge.

You can see the tell-tale fly features: a single pair of wings, compound fly eyes, and short antennae. They presumably evade the attention of fly predators by looking like wasps. They actually are helpful pollinators and their larvae eat aphids. All good.

I am not often impressed by an insect's personality, but I felt like that fly wanted to be noticed. Later I read that in some parts of the country hover flies are called "good news bees" because of their habit of hovering nearby as if wanting to tell you something.

There is a lot of activity on milkweed plants this time of year. I wrote a blog about some of the members of the milkweed community in October of 2011. You can see that blog by clicking here.

Today I saw this late instar monarch caterpillar. Its head is on the right. It was eating voraciously, bulking up for its pupal stage, which will come soon. It will pupate for about two weeks and then emerge as a butterfly to begin its long migration south. Click to enlarge.

The plants were covered with oleander aphids like this one.

A few of the aphids had wings. There is one in the upper right of this photo; winged individuals can disperse to nearby stems and pods to establish new populations. Click to enlarge the photo and you will see that there is a caterpillar-like organism among the aphids. It is the larva of a syrphid fly; it will  grow up to become a hover fly (also called flower fly). In its larval stage it eats aphids. No shortage of those around here.

A closer look at the fly larva. It is easy to mistake for a caterpillar, or even a plant part. Stealthy!

As I was clicking pictures of this cluster of milkweed bug nymphs, I got a surprising message from them -- they knew they were being watched and they did not like it. See the picture below. They all ran around to the other side.

Stop looking at us!

Flower flies. Click to enlarge.

It is technically still winter, but warm temperatures and blossoming flowers say it's spring in Brooklyn. And flower flies are back!
Flies are not all creatures of garbage and decay. Flower flies visit flowers to eat pollen or drink nectar. There are about 6000 kinds worldwide and many of them are beautiful. They are also called hover flies, for their helicopter-like flight, and syrphid flies or syrphids for their scientific family, Syrphidae.

Black-and-yellow colored flower flies are often mistaken for wasps or bees. That's all according to plan! They are Batesian mimics; although they are harmless, they resemble more dangerous insects. Predators are likely to leave them alone and look for easier prey.

A wing count tells us that they are flies, with just two wings; if they were bees or wasps they would have four. Look closely at newly opened flowers and you will probably find flower flies.