托福听力考试背景知识综合辅导(四十六)

Big eyed Bug Rearing

Natural History
Big-eyed bugs are true bugs in the order Hemiptera. The two most common species are Geocoris pallens and Geocorcis punctipes. Both are predators and occur in many habitats, including fields, gardens, and turf grass. Big-eyed bugs are considered an important predator in many agricultural systems and feed on mites, insect eggs, and small insects such as pink bollworm, cabbage loopers and whiteflies. Adult Big-eyed bugs are small (about 3 mm) black, gray, or tan with proportionately large eyes. Eggs are deposited singly or in clusters on leaves near potential prey. They develop with incomplete metamorphosis (there is no pupa) and take approximately 30 days to develop from egg to adult depending on temperature. Both nymphs and adults are predatory, but can survive on nectar and honeydew when prey are scarce. Big-eyed bugs, like other true bugs, have piercing-sucking mouthparts and feed by stabbing their prey and sucking or lapping the juices. Although their effectiveness as predators is not well understood, studies have shown that nymphs can eat as many as 1600 spider mites before reaching adulthood, while adults have been reported consuming as many as 80 mites per day.

Rearing
Big-eyed bugs are easy to rear. Adults can be purchased (see Suppliers) or collected in the wild by using a sweep net in a local alfalfa field, roadside or other lush area that may have potential insect prey. A Petri dish provides adequate housing when a piece of paper towel or filter paper is placed in the bottom and cut to fit the dish. Adults and nymphs should be housed separately as the larger individuals will eat the smaller ones. If you plan on raising large numbers of them, you may want to invest the time in making an artificial diet (see Cohen in the References), however they will also do well with fresh insect eggs (purchased), whitefly nymphs or aphids provided every few days. For moisture, place a one-inch piece of fresh green bean (replaced every couple of days) in the dish. A small piece of cotton placed in the adult cage provides a place for oviposition as well as a hiding place. Periodically remove the cotton from the cage (eggs are pale orange) and place it in a new cage with a fresh piece of green bean. In a week to ten days, nymphs will emerge and a protein source (eggs, diet, etc...) will need to be added. When cages become dirty or moldy, transfer adults and nymphs to a fresh cage. Adults can be handled with soft forceps or with a small soft paintbrush. Nymphs should be handled with a soft brush only.