Garden Insect Identification: Immatures

Today we're going to briefly discuss the identification of insects that aren't adults yet.

I. Incomplete metamorphosis

milkweed-bugs-top

Immature insects are not always easy to identify. For example, what were our red mystery insects last week?

cropped-milkweed-bug

Zooming in we can see this bug has its proboscis, or straw-like mouthparts, stuck into the plant. It is a true bug. In fact, as Sara pointed out, these red bugs are the nymphs of milkweed bugs.

You can tell they are not adults because of the short, dark pads where the wings would be. Only adult insects have wings. Insects that don't change drastically in shape between molts, or insects with incomplete metamorphosis, have a series of stages called nymphs.

milkweed-bug-great

In this case the nymphs are likely to be small milkweed bugs, Lygaeus kalmaii, which are the most common kinds in our yard. Notice the two white spots on the black part of the wings of this adult.

How can we know for sure which bugs the nymphs will turn into? One way is to have patience and wait until they become adults. Adults are much easier to identify via field guides.

assassin-bug-nymph-even-better

The nymphs may be different colors than the adult. That stripy-legged youngster is the nymph of an assassin bug.

assassin-bug-on-brittle-bush-leaf-1

An adult assassin bug lacks the stripes. However, you can still recognize the overall shape.

stinkbug-nymphs-done

The nymphs in this cluster have just hatched out of their eggs. These are shield bug nymphs. Once again, the insects lack wings (see adult shield bug)

cicada-nymph1

Other groups that have nymphs include cicadas, like the one above. Cicada nymphs may live for years under the ground.

grasshopper-little

Grasshoppers also have nymphs, as do aphids, leafhoppers, praying mantids and cockroaches, among others.

II. Complete metamorphosis

A. Lepidoptera

Although many of us recognize the life stages of a butterfly, some of the life stages of other orders with complete metamorphosis can be tricky.

moth-pupa

Ever found one of these in the soil? Do you know what it is? It is the pupal stage of a moth (see post about moth life cycles)

B. Coleoptera

lady-beetle-pupa

What about these orange and black insects? The insects in the photographs above turn into lady beetles, similar to this one:

ladybeetle1-seven-spot

Most of us recognize that adult lady beetles are beneficial insects. The youngsters are beneficial as well (more about lady beetle life cycles).

Some beetle larvae look more like worms or caterpillars. This video has a nice summary of the life cycle of darkling beetles (its larvae are called mealworms).

 

c. Hymenoptera

sweat-bee-1

What are the "grubs" in this photograph? Those are sweat bee larvae (more photographs of the sweat bee life cycle at Wild About Ants).

ant-life-cycleAnts also have eggs, larvae and pupae, sometimes in cocoons (graphic from Wild About Ants)

Unfortunately, we only have space for a brief introduction to immature insect and life cycles here.

Where can you get further help identifying immature insects?

A classic book, How to Know the Immature Insects by H.F. Chu (1949) is available online or for download at Biodiversity Heritage Library. It is a key with black and white line drawings, and requires some knowledge of entomological terminology.

BugGuide.net is a wonderful resource. It may take a bit of persistence, but they have photographs of many, many insects, often identified to species. Click on the insect that most resembles yours in the left sidebar and then keep going. Try the images tab as well.

Insect Identification.org is a bit easier to use, but does have large ads

Here at Growing with Science we have posts about how to recognize the 5 major orders of insects, as well as the Bug of the Week archive.

Have you ever been mystified by an immature insect? What did it turn out to be?

4 thoughts on “Garden Insect Identification: Immatures

  1. Nice post. I've noticed that many true bug nymphs cluster and are bright colors.
    It took me a while to identify sawfly larvae, they look like caterpillars, have fly in the name, but are in the bee and wasp insect order.

  2. Post author

    Oh yes, sawfly larvae are difficult. There are a few leaf beetle larvae that look quite similar to caterpillars and sawfly larvae, too.

  3. Jan Bruce

    have never seen these red beetles before...they have ravished my Asiatic lilies??? where did they come from? CHINA???? don't like what they have done to my garden

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