ENTOMOLOGY

SANITARY ENTOMOLOGYcentipedes have a poison sac opening on the front pair of legs. Thescorpion stings with the tip of its tail. The bee, wasp, and ant stingwith the ovipositor. M~ny of these injuries are very painful., CertainIepidopterous larvre are pro'vided with barbed hairs which containpoisonous secretions, as the brown tail moth larva, and the larvre ofLagoa. H yperchiria io, etc. Some insects emit poisonous secretionswhich blister (Meloid beetles). Some of the South American honey bees(Trigona) store poisonous honey. .5. Paralysia.-The bite of several species of ticks (Dermacentoranders()lfli (V{ffl.uatus), for example, may cause paralysis with sometimesfatal results. Some spiders, ants, bees, wasps, and. caterpillars inflictsuch a poisonous wound that temporary paralysis of the limb follows.6. Dermatosis.-Direct attack upon the ~ody of men and animals,and parasitism thereon, is not unusual. We have as striking examples'the dermatoses caused by lice (pediculosis), by the chigoe, the redbug (chiggers), the Dermatobia hominis, creeping worms, scab anditch mites (acariasis). Many of these attacks have serious after results,as for instance an acute attack by the chigoe may result in ainhum, theloss of a toe or a foot. Many secondary diseases obtain access to thebody through the skin attack of insects.7. Myiasis and similar internal aftacks.-Under'this heading are tobe considered cases in which insects are present in the tissues of internalorgans of the body. The occurrence of insects has been recorded inorgans of the head, in the intestinal canal, the reproductive organs,and the body wall. When the insect is a fly the disease is called Myiasis.When a beetle is the cause, the disease is called Canthariasis, and if alepidopterous larva is responsible it is known as Scholeciasis. Manyspecies of flies have been recorded as occurring in the human body. Thesewill be studied in detail in a later lesson.(II.) Diseases carried by insects.-The ways in which insects maycarry diseases are very diverse, due to the great differences not only inthe habits of the insects, but also of the disease organisms and thehosts.1. Diseases carried by insects to food.-When insects carry diseasegerms to food or water we speak of the transmission as contaminative.Cont~minative transmission of disease organisms to food by insects isnaturally the simplest mann~r of transmission. This is necessarily doneby insects which frequent excretionary substances and also visit foods,such as certain flies, ants, roaches, and beetles. It is obvious that wemust lo.ok upon all insects which breed in fecal matter, sputum, etc., aspotential disease carriers. Considerable research has already been conductedto prove the actual role of many species of coprophagous insects.The role of the carrier may eithE'r be mechanical or biological.