Mike McSparrin, age 11, of Goltry, Oklahoma, for his question:

Do all insects lay eggs?

Some years ago, many scientists would have answered "Yes, all the half million or so known insects lay eggs." Now the list of known insects has grown to about 700,000. And, what's even more interesting, researchers have learned a lot more about the old familiar types. We now know some lay larvae and a few species actually give birth to small adult insects.

Let's hope you enjoy impressive words, because in this case a few scientific terms help to clarify a rather complicated story. It's no problem to cope with them when you know that "ova," the plural of "ovum," means "egg." "Parous" means "bearing" or "giving birth" and "viva" is "related to life," or "alive." Most insects are oviparous . ¬and nobody has to tell you that this means that the females lay eggs.

A few viviparous species actually nourish the eggs through the larva stage within the female's body    and give birth to small, living adults. In another group, the eggs are retained in the female's body until the larvae are ready to hatch. This is midway between the oviparous and viviparous methods. Insects that bear live larva are ovoviviparous.

In the insect world, these stages of development are most dramatic. All insects progress through distinct egg, larva and adult stages. Some also change by complete metamorphosis through an extra pupa stage. The adults can afford to lay numerous eggs and let their offspring cope with spells of drought, cold and other hardships    either in the egg or pupa stage. But apparently a few species found it necessary to take added precautions.

The list of non conformists includes several scale insects and mealybugs, aquatic insects, aphids and some types that live as parasites on other animals. The scale insects encase themselves and their food supplies in hard secretions, where they live and die. In certain ovoviviparous species the female retains the eggs to the larval stage. In some cases, she dies and the larvae are protected by her body and skins of her past moltings.

Certain mealybugs also are ovoviviparous. So is the bat tick, alias the bat louse. This wretched female burrows into her host's skin and her body becomes a sac where the eggs develop and hatch. The pesky larvae crawl through the hole in the bat's skin and proceed to dine on their host.

The females of certain fly and aphid species contain special glands to nurture their offspring. They retain the eggs through the larval stage and give birth to young adults. These and several aquatic mayflies are viviparous insects.

Almost all insects lay eggs and leave them to take their chances. The species that do not are oddities, even in their own groups. Only a few of the parasitical ticks are ovoviviparous, and only a few species of the aquatic mayflies.