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ENTOMOLOGY: BASIC ENTOMOLOGY [continued]

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  MG Manual Reference
Ch. 3, pp. 13 - 14
[ Basic Entomology: introduction | anatomy | development | classification | specific groups; coleoptera, lepidoptera, diptera, hymenoptera, hemiptera, homoptera, orthoptera, isoptera, dermaptera, thysanoptera, thysanura, collembola, other insects, relatives, other classes ]


SPECIFIC GROUPS [continued]
Figure 9. The developmental stages of the true bugs

Eggs
Eggs

Nymphs
Nymphs

Adult
Adult

ORDER HEMIPTERA -- TRUE BUGSTop

a. Have simple metamorphosis. The adults and nymphs resemble each other.
b. Have two pairs of wings. The top pair are thickened or leathery at the base and membranous at the tips (hemi = half, ptera = wing). The under wings are membranous.
c. Adults and nymphs both have piercing and sucking mouthparts, and both cause damage in plant-feeding species. Other species of true bugs are predators.
d. Many have glands that produce odors when the insects are threatened.
e. True bugs have a triangular plate centrally located between the thorax and abdomen on the back.
Kissing bugs or conenose bugs are medically important true bugs that feed on blood. Normally found associated with pack rats, they may enter houses where they bite humans at night. The proteins in the saliva may cause allergic reactions in some individuals. Other true bugs that enter houses are often mistaken for kissing bugs, and alarm homeowners. For example, false boxelder bugs are common in Arizona, and frequently enter homes. They are gray-brown to black with red lines on the under surface and on the lower portion of the outer wings. But they do not have the distinctive projecting "nose" found in all conenose bugs.
Leaf-footed bugs are common pests of landscape plants. The bugs are pinkish orange with black legs as nymphs. The adults are up to 1 inch long, with hind legs flattened out, resembling a leaf. They feed on fruits and nuts, such as pecans, tomatoes, pomegranates, and occasionally citrus. They may carry a bacteria that causes pocket rotting damage to fruit.
Stink bugs are shield-shaped bugs about 1/2 inch to 1 inch long, so-named because they produce a variety of odors when captured. Some species are predaceous (feed on other insects) and others are plant feeders, so it is important to have them identified. Predatory true bugs include big-eyed bugs, minute pirate bugs, assassin bugs, ambush bugs and damsel bugs.
Figure 10. The developmental stages of scales


Scales

ORDER HOMOPTERA -- SCALES AND APHIDSTop

a. Soft-bodied insects with sucking mouthparts.
b. Some adult forms have wings, others do not. For example, the male California red scale has two pairs of wings and resembles a tiny wasp. The adult female California red scale is flattened with a waxy covering and has no wings.
c. Have simple metamorphosis.
d. Many carry plant pathogens which can be transmitted during feeding.
e. Most species excrete a sugary residue called honeydew, which in turn leads to sooty molds.
Scale insects are often hard to recognize because they do not look like insects at all. They are flattened, circular or ovoid bumps covered by a waxy or hardened scales. Most aren't serious pests, although they may cause unsightly blemishes. It is interesting to note that shellac is derived from the native lac scale. The cottony cushion scale attacks shade plants such as Pittosporum, Euonymus, and sometimes hibiscus. Their numbers can mushroom quickly.
The cochineal scale grows at the base of needles of prickly pear cactus forming a mass of stringy whitish globs. This insect was highly prized and cultivated by early explorers because the crushed bodies make a colorfast dye.
Many different types of aphid occur in Arizona. Oleander aphids are a yellow species that appear in the spring on the tips of oleander. The pea aphid is a plump, green species found on alfalfa, peas, clover, sweet clover and other herbaceous legumes. Many species of aphids attack roses, particularly the new growth. They may cause chlorosis (a yellowing of the green tissue).
Whiteflies are not flies at all, but close relatives to scales and aphids. The immatures are flattened, scalelike forms that suck juices from the undersides of leaves. The adults are about 1/16 of an inch long and are covered with a white, waxy powder.
Mealybugs are oval, flattened insects that cluster on the stems of a variety of houseplants, and also a few landscape plants. They are soft-bodied insects, often pinkish in color with a covering of white, powdery wax. They suck plant juices, which may slow plant growth or cause wilting.

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