ENTOMOLOGY

MYIASIS-TYPES OF INJURY, LIFE HIS'l't"';lY, HABITS 191The life history of the common bot fly is about as follows: The eggsare attached to the hairs of the host, mainly on the legs, but frequentlyon other parts. These are ready to hatch in from nine to forty days.The larvre are removed from the eggs by the biting and licking of thehost. They take up their abode in the stomach, remaining attached to themucous coatings of the pyloric end of this organ until fully grown severalmonths later. They then detach and pass out with the manure,pupate ncar the surface of the ground and produce the so-called bot fliesthree to six weeks later. The cycle is completed in about a year. Thelife histories of the nose fly and throat bot are similar but differ especiallyin the method of oviposition. The former deposits its eggs, which arenearly black, on the very minute hairs around the lips. The young larvregain access to the mouth and develop as in the common bot fly, but beforepassing out they usually catch hold of the mucous membrane of therectum and are often seen protruding from the anus a few days beforedropping. The annoyance produced by the oviposition of this fly isvery severe. The throat bot deposits its eggs mainly under the jaws andthe larvre are often found in the duodenum and also attach in the stomach.In addition to the annoyance produced at the time eggs are deposited,heavy infestations in the stomach interfere with digestiun and cases arerecorded where the larvre caused death by stopping the pyloric opening.The irritation of hots, which may be present in numbers exceeding 1,000,must be detrimental to the host. The throat bot also attaches in thepharynx in its early stages and is accredited with causing the death ofanimals from this habit.Cases of dermal myiasis in man attributable to these species havealready been mentioned. European writers Jlave also reported the occurrenceof larvre of Gastrophilus in the eye of man.Passing to those forms which arc more or less accidental, the Sarcophagidaedemand first attention. Hasseman has reported a case inwhich an entire family was infested with the larvre gf Sarcophaga lzaemorrhoidalis,the maggots being passed in considerable numbers during warmweather. Numerous other similar instances have occurred and in practicallyevery instance they are traceable to leaving foods exposed to fliesbetween meals. Since the Sarcophagids deposit living larvre on meats,etc., they may be easily overlooked.Cases of intestinal myiasis due to Eristalis larvre are common in thiscountry. A good summary of these cases has been made by Hall & Muir.It appears that they sometimes give rise to acute colicky pains but noserious symptoms. As is well known, the rat-tail larvre are to be foundin decaying vegetation and in water, and the source of infestation mustbe through the swallowing of uncooked and poorly cleaned food such aswatercress and lettuce, a.nd the drinking of unclean water. The follow-