Bird-lice

(Order Mallophaga.)

The very strange parasitic insects which belong to this order are generally known by the name bird-lice. They differ widely from true lice of the order Heteroptera, suborder Anoplura, and in spite of the fact that they are known as bird-lice some of them occur on mammals. From this fact it is evident that the popular name bird-lice is a misnomer, and it will be well to adopt Sharp's suggestion and call the Mallophaga "biting lice" as opposed to the sucking lice of the suborder Anoplura.

They are very small and have no wings, and the principal characteristic which distinguishes them from the true lice is that instead of having apparently sucking mouth-parts they have biting mouth-parts. They do not suck the blood as do the true lice, but feed upon the feathers or hair of the birds or mammals upon which they are found. Their metamorphosis is incomplete. The body is very greatly flattened, and generally hard; the head is large and flat; the antennae are short, and three to five jointed; the eyes are simple; the jaws are usually toothed and pointed; the legs are strong, and, curiously enough, the front legs are short and are used only in carrying food to the mouth. When at rest, they project forward beneath the head. The whole body is usually rather hairy.

The eggs are elongate oval and are fastened singly to the feathers or hairs of the host. The young issue by breaking off a circular lid at the larger free end of the egg. The duration of the egg stage is not known.

The young lice when first hatched look much like the full grown lice, except that the head is comparatively larger, and the markings of the body are absent or dull. Just before the last molt some individuals are quite as large as the adult specimens.

The question as to whether they really draw blood has been carefully studied. There will frequently be seen a large dark blotch indicating some opaque contents to the stomach, but a careful examination on dissection has shown that this blotch is composed of bits of feathers. One species is said by Kellogg to live in the pouch of a pelican, where, of course, there is no hair, and about the portion of the membrane to which the lice cling the surface is raw and bloody, but here Kellogg thinks that the food is simply the epidermal scales of the inner wall of the pouch.

Such of these bird-lice as occur upon domestic fowls, while not serious pests, undoubtedly cause poultry considerable annoyance simply by the irritation of the skin by the sharp feet of the parasites. After a hen affected with bird-lice dies, the insects either die or attempt to leave her body by crawling slowly toward the head. Considering that they do not feed upon the blood, but simply upon the feathers, it is curious that they should die after the death of the hen. Kellogg suggests that their death is probably due to the lack of animal heat to which they have been accustomed during the life of the host.

Aquatic birds are affected with bird-lice quite as abundantly as those which never enter the water, and it would not be strange if in the lice affecting such birds should be found some modification of the breathing apparatus, but there is no such modification and they are doubtless protected by the close feathers, so that they always have a sufficient supply of air even when the bird or a portion of its body remains under the water for some time.

It is very rare that bird-lice ever leave the body of the host, but they do migrate from one bird to another whenever two birds come in contact, as during the nesting season or among birds of gregarious habits.

In many cases a given species of Mallophaga will be found to be confined to a given species of bird or mammal, but in other cases one species of parasite will be found upon two or more species of birds. Curiously enough, some of these parasites are found in Europe on birds which differ from those upon which identically the same species of parasite is found in North America. Several species may occur upon the same bird; for example, at least five species belonging to three distinct genera have been found upon the common fowl. Nearly all of these are cosmopolitan insects and have been carried upon fowls to all parts of the world. Chickens hatched in an incubator should be absolutely free from lice and remain so until they join company with older fowls. There is little doubt that the habit which hens have of bathing themselves in dust is an effort on their part to get rid of the irritation caused by these creatures.