Thursday, February 26, 2009


I had been wanting to do a mini-life cycle entry about holometabolous insects, particularly lady bugs, because I have in my possession a few lady bug specimens and one of their pupa. Today I captured a live lady bug larvae, which I photographed and then released into the garden. To preface, holometabolous insects include the major orders of insects, such as Diptera (flies), Lepidoptera (butterflies and moths), Hymenoptera (wasps, bees, ants), and Coleoptera (beetles). Holometabolous means that they undergo a complete transformation from a larval form to an adult form, with no intermediate forms. So, a caterpillar stays a caterpillar for a while, forms a cocoon, and emerges with wings and different body structures. Often the larvae and the adults have different diets and habitats, allowing the insect to exploit various environments. This is in contrast to hemimetabolous insects, which go through several progressive molts, gradually assuming the adult form. This can be seen in Orthoptera (grasshoppers, katydids, crickets).

Coleoptera; Polyphaga; Cucujoidea; Coccinellidae; Coccinella septempunctata
Common Name: Seven-Spotted Lady Beetle

Coleoptera; Polyphaga; Cucujoidea; Coccinellidae; Harmonia axyridis
Common Name: Multicolored Asian Lady Beetle

The first image is the larvae of the lady beetle. Approximately 6 mm long, they have the same diet as the adult - aphids and other small leaf-sucking insects. The larvae of different lady beetle species mostly vary in their black and orange coloration. Eventually they form a pupa, and emerge as an adult lady beetle. The first image is the seven-spotted lady beetle, which usually is a brighter orange than a dull red, but I suspect freezing affected a change in the color. The second image is the multicolored Asian lady beetle, which was artificially introduced into North America for the purpose of controlling aphids (1916). It was introduced several more times, and is the variety often purchased from gardening stores. This insect is one of the first, and most successful (while remaining beneficial), introduced biological control agents. What marks the success of an introduced species is whether its numbers remain at a reasonable level, the insect does not harm beneficial native species, and remains specific for the pest it was originally introduced with the purpose of controlling. In some places they can be a nuisance simply because they are in large numbers, but they do not carry disease or damage property. The adults are capable of biting if handled, but do not break the skin, and release an strong smelling orange fluid to deter predators.

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