Sounds like Grubs(Warbles) to me. Ruins the portion of the hide that the grub migrages through. As a kid I remember using a pop bottle to "pop" the grubs out of the cows back. (Yes, we had limited means of entertainment).
Cattle Grubs
Two species of cattle grubs are found in the United States, the common cattle grub and the northern cattle grub. The common cattle grub is found in Florida; however, the northern cattle grub is usually found only in cattle shipped into Florida from other states.
The common cattle grub ( Figure 8 ) lays its eggs chiefly on the hair of cattle, attaching 5 to 15 eggs to a single hair. No pain is inflicted at the time of oviposition. In the spring (February, March, April, May) cattle gallop madly for water or shade to escape the northern cattle grub (gadding). It is apparently a reaction to the sound produced by the bee-like fly in flight.
CREDITS: J. F. Butler, University of Florida
Figure 8. Cattle grub.
Eggs hatch within about 4 days, and the maggots burrow through the skin. Migration of the first stage larvae of the common cattle grub is through connective tissue, assisted by enzyme secretion. Common cattle grub larvae locate in the mucous membrane of the gullet. Larvae of the northern cattle grub locate in the spinal cord. During the early fall in Florida (October-November), migrating first stage larvae begin reaching the backs of cattle where they cut or digest a breathing hole through the skin and form a warble.
First stage larvae molt in the warble formed in the back to the second stage in 3 to 4 days. The second stage larva molts to the third stage then grows rapidly, feeding on pus, necrotic cells and secretions from the wall of the warble or cyst. One to 2 months are spent in the warble to attain full larval growth. The grub then squeezes through the breathing hole in the skin and drops to the ground to pupate. Pupation occurs in 2 to 3 days with the pupal stage lasting 20 to 60 days, depending on the temperature. The complete life cycle requires about a year.
The larvae produce two types of injury. First there is irritation caused by larval migrations in the body of the host and later by emergence from beneath the skin. Second, the escape of the larva from the warble leaves an open, running wound that is persistent and subject to secondary infection.
Economic losses are, however, much more important. Milk production may be reduced as much as 10 to 20 percent and loss of weight resulting from the wild efforts of the animals to escape from the flies may be considerable. The value of the carcass depreciates because flesh becomes greenish-yellow and jellylike in appearance and unfit for consumption where the grubs are located. The value of the hide is also reduced because of the holes cut in the skin.
Timing of treatments for control is important. The grubs must be killed before they reach the gullet or spinal cord, because killing grubs in these areas can cause swelling, and paralysis or death. "Cut-off dates" have been established in the United States for grub treatment. In Florida, grub appearance in the backs or gullets of animals occurs early, so the "cut-off date" has been set at August 31.
The treatment period includes that time after which egg hatch has ceased until larvae have moved up to, but not into, the back or gullet region. Sprays, dips, feed additives, and pour-ons are all recommended for cattle grub control although pour-ons give best results.
)) i will try to find the camera and get some pictuers
