22 SANITARY ENTOMOLOGY 



centipedes have a poison sac opening on the front pair of legs. The 

 scorpion stings with the tip of its tail. The bee, wasp, and ant sting 

 with the ovipositor. Many of these injuries are very painful. Certain 

 lepidopterous larvae are provided with barbed hairs which contain 

 poisonous secretions, as the brown tail moth larva, and the larvas of 

 Lagoa, Hyperchiria io., etc. Some insects emit poisonous secretions 

 which blister (Mcloid beetles). Some of the South American honey bees 

 {Trigona) stote poisonous honey. 



5. Paralysis. — The bite of several species of ticks {Dermacentor 

 andersoni {venustus), for example, may cause paralysis with sometimes 

 fatal results. Some spiders, ants, bees, wasps, and caterpillars inflict 

 such a poisonous wound that temporary paralysis of the limb follows. 



6. Dermatosis. — Direct attack upon the body 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 red 

 bug (chiggers), the Dermatobia homims, creeping worms, scab and 

 itch mites (acariasis). Many of these attacks have serious after results, 

 as for instance an acute attack by the chigoe may result in ainhum, the 

 loss of a toe or a foot. Many secondary diseases obtain access to the 

 body through the skin attack of insects, 



7. Myiasis and similar internal attacks. — Under this heading are to 

 be considered cases in Avhich insects are present in the tissues of internal 

 organs of the body. The occurrence of insects has been recorded in 

 organs 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 a 

 lepidopterous larva is responsible it is known as Scholeciasis. Many 

 species of flies have been recorded as occurring in the human body. These 

 will be studied in detail in a later lesson. 



(II.) Diseases carried by insects. — The ways in which insects may 

 carry diseases are very diverse, due to the great differences not only in 

 the habits of the insects, but also of the disease organisms and the 

 hosts. 



1. Diseases carried by insects to food. — When insects carry disease 

 germs to food or water we speak of the transmission as contaminative. 

 Contaminative transmission of disease organisms to food by insects is 

 naturally the simplest manner of transmission. This is necessarily done 

 by insects which frequent excretionary substances and also visit foods, 

 such as certain flies, ants, roaches, and beetles. It is obvious that we 

 must look upon all insects wliich breed in fecal matter, sputum, etc., as 

 potential disease carriers. Considerable research has already been con- 

 ducted to prove the actual role of many species of coprophagous insects. 

 The role of the carrier may either be mechanical or biological. 



