238 EXPERIMENTAL FARMS. 



Prof. Riley graphically describes what this meant, in the First Report of the 

 United States Entomological Commission on the Rocky Mountain Locust, page 319 : 

 " The most common of the parasites which prey on the locusts internally are the larvae 

 of certain flies belonging to the genus Tachina^ gray-coloured, two-winged flies having 

 very much the general appearance of house-flies. 



" These Tachina-flies firmly fasten their eggs — which are oval, white, and opaque, 

 and quite tough — to those parts of the body not easily reached by the jaws and legs of 

 their victims, and thus prevent the eggs from being detached. The slow-flying locusts 

 are attacked while flying, and it is quite amusing to watch the frantic efi'orts which one 

 of them, haunted by a Tachina-fly, will make to evade its enemy. The fly buzzes 

 ■around, waiting her opportunity, and, when the locust jumps or flies, darts at it and 

 attempts to attach her egg under the wing or on the neck. The attempt frequently 

 fails, but she perseveres until she usually accomplishes her object. With those locusts 

 which fly readily, she has even greater difficulty ; but though the locust tacks suddenly 

 in all directions in its efforts to avoid her, she circles close around it and generally suc- 

 ceeds in accomplishing her purpose, either while the locust is yet on the wing, or, more 

 often, just as it alights from a flight or a hop. The young maggots hatching from the.-e 

 eggs eat into the body of the locust, and after rioting on the fatty parts of the body^ — 

 leaving the more vital parts untouched — they issue and burrow in the giound, where 

 they contract to brown, egg-like puparia, from which the fly issues either the same 

 season or not till the following spring. A locust infested with this parasite is more 

 languid than it otherwise would be ; yet it seldom dies till the maggots have left. 

 Often, in pulling off" the wings of such as were hopping about, the bodies have presented 

 the appearance of a mere shell filled with maggots ; and so efficient is this parasite that 

 the ground in parts of the Western States is often covered with the Rocky Mountain 

 Locusts dead and dying from this cause." 



There are several species of these Tachina-flies, and we have bred two kinds during the 

 past summer, one from specimens sent by Mr. Richardson, and another much larger species, 



Exorista Jlavicauda, Riley (Fig. 7.), from several localities. 

 This last named species is of great interest from the fact 

 that it is the enemy of the Army-worm, which, above all 

 others, brings down the numbers of that plague when it 

 increases unduly. There are also, in addition, parasitic 

 species of flesh-flies (Sa7-cophaga) which resemble the above 

 very closely, but may be distinguished by their antennae 

 being hairy instead of smooth. 



Hair-worms. — Hair-worms, or Hair-snakes, as they 

 are sometimes called, are objects of great curiosity, not only 

 Fig. 7.— Tachina-fly, to those who know nothing of their habits, but also to all 



who have studied their remarkable life history. Their great abundance in some places 

 during the past summer has been remarked by many correspondents, and the good 

 work they have done as parasitic enemies of many kinds of grasshoppers, crickets and 

 other injurious insects, renders it advisable to give a short outline of what is known 

 about them. There are many misapprehensions as to the true nature of these creatures, 

 notably the erroneous ideas that they are related to the true snakes or that they are 

 horse-hairs which by some mysterious process have become capable of living and 

 moving. Snakes, however, belong to the much more highly organized Vertebrates, or 

 animals with backbones, while the Hair-worms are raemljers of the Entozoa, or intestinal 

 worms, a section of the Articulates which have their bodies merely divided into joints. 

 The supposition that a horse-hair or any other dead organic matter 

 can ever become a living creature, is too absurd to need more than 

 mention. 



Tt must be acknowledged that there are some gaps in our knowledge 



Fig. s.— Egg'of Corc^ms of the life history of Hair-worms concerning which it seems impos- 



coiitaininf? a fully de- sible to make any suggestion. It is known positively that the eggs 



h^i g^h 1 y '"magnified ^^^o" ^•) ^"^^ ^^^*^ ^"^ water and that the young worms begin their 



(After Leidy.) lives as free-moving animals, which have been actually seen to 



