Lice infest numerous vertebrate species and spend their entire life on their hosts. Their life cycles and details of their biology are consequently highly varied. Of the many species that we could discuss, we arbitrarily pick two sucking lice: hog lice and cattle lice.
The cattle louse life cycle requires three to four weeks during cold weather. Carrier animals in the herd seem to harbor infestations throughout the year. Low numbers exist during warm months, but with the onset of cooler temperatures high numbers soon develop. Ten or more lice per square inch have significantly reduced weight gains in cattle while light infestations did not.
Four species of cattle lice are commonly found on cattle. Three species are sucking lice while the fourth is a biting louse. Sucking lice consist of the short nosed cattle louse (above), long nosed cattle louse Linognathus vituli, and the little blue louse, Solenopotes capillatus. The fourth species is commonly referred to as the cattle biting louse, Bovicola bovis. Sucking lice are more important from an economic standpoint.
Lice should be controlled in late fall rather than waiting until spring when obvious symptoms develop. Herds with a history of springtime lice problems should receive a preventive treatment in the fall. Introducing new cattle into the herd may spread lice. Inspect cattle by parting the hair and examining the skin for lice. If two or more lice are found per four-inch area examined, treatment should follow. Ringworm is sometimes mistaken for lice infestations. If cattle appear lousy after lice treatments, ringworm may be involved.
Adult hog lice are frequently found in the folds of the neck and jowls, inside and at the base of the ears, on the inside of the legs, and on the flanks and backs of hogs. Most of the nymphs occur on the head region.
After feeding and mating, each female lays three to six eggs per day and about 90 eggs in all. Eggs are deposited along the lower half of the sides, on the back of the ears and on the neck, the shoulders, or the flanks. They hatch in 12 to 14 days, though in cool weather they may take 20 days. The young lice molt 3 times in 10 to 12 days as they grow. Feeding takes place in the more tender areas of the body. Hog lice are mature and ready to lay eggs about 12 to 14 days after hatching. The entire life cycle, from egg to egg-laying adult takes from 20 to 48 days. Six or more generations may be completed each year.
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