Fig. 222.—Bluebottle fly and young.
Among the many species of flies some are bloodsuckers, as the horse flies. The robber flies are the hawks of the race, carrying off other insects, even large dragon flies. The many species of horse flies attack horses and cattle, and the animals are often driven to a frenzy by their approach. An entire herd will recognize the approach of these insects and stampede. Many of the flies deposit their eggs upon the hairs or nostrils of horses. Flies exist in countless varieties, from harmless creatures to some in Africa which are deadly to cattle and horses; from the ordinary fly whose larva lives in cheese to others which thrive in alcohol and wine. In California the larva of one species is found in Lake Mono, where no other animal can live. Hundreds of bushels of them are sometimes washed upon the beaches, constituting a favorite food for the Indians.
The warfare declared against mosquitoes in America, suggested by Dr. Howard, has attracted widespread attention to these insects, which have rendered many localities absolutely uninhabitable. A Florida physician informed me that in a certain locality horses had been killed by these insatiate bloodsuckers, which are now known to be the carriers of the germs of yellow fever. Over almost every pond or pool in summer they may be seen in countless numbers, filling the air with their disagreeable music.
Fig. 223.—Proboscis of a mosquito.
The proboscis, or sucking weapon, of the mosquito (Fig. 223) is an innocent-appearing object when closed; but when the sheath is open it displays a series of scimeter and sawtooth daggers (Fig. 224), which fully explains the torture of the mosquito bite or that of the gnat which crawls up one's sleeve (Fig. 225). In all these extraordinary weapons we find the same organs, the labium, labrum, and others, but with greater or less development, according to the nature of the insect.
Fig. 224.—Proboscis of a mosquito open.
Fig. 225.—Biting organs of a gnat.