434 THE GAD-FLY. 



ONE of the wonders of natural science is the ARMY-WORM (Heerwurm). At first sight, it 

 appears to be a single being, but by closer observation it will be seen to consist of a vast mul- 

 titude of larvae, or caterpillars. There is a European and an American Army-worm, distin- 

 guished from each other by the nature of the tiny creatures which collect in a body for pro- 

 cession or migration ; the one being a collection of the larvae of the small light yellowish gnat 

 (Sciara militaris), belonging to the family MycetopMlidcB of this class, while the other consists 

 of the caterpillars of one of the moths of the family Noctuidce. 



When in such a large collection, the larvae of the Sciara militaris move forward in a 

 snake-like manner. They look pallid, and are kept closely together by their mucous surfaces, 

 so that they really appear as one body. So strongly do they stick together, that the tail-piece 

 of the worm may b'j lifted with help of a stick for a moment without becoming refracted. 

 The faculty of moving on consists in the uniform motions of all the larvae. Every one shoves 

 forward with the back of the body, and then stretches out the fore-part as if feeling. The 

 whole appears like a little stream slowly gliding along. 



Sometimes this larvae-procession has to overcome obstacles in its way which often cause a 

 dissection. Small hindrances the Army-worm surmounts, but larger ones cause a temporary 

 disunion. Sometimes one part of the mass of bodies disappears under leaves, but generally a 

 reunion takes place. A break by force, caused, for instance, by the hoofs of a horse, or by the 

 wheels of a wagon, soon becomes joined, just as is the case with the so-called procession-cater- 

 pillar of the moth Cnethocampa processionea, belonging to the family Bombycidce, of the 

 class Lepidoptera. 



For centuries, the mysterious movements of the Army-worm have given rise to all kinds 

 of superstitious beliefs among the people of Europe, where from time to time it was seen in 

 Silesia, Thuringia, Hanover, Denmark, Norway, and Sweden. They predicted luck or mis- 

 fortune from its appearance, some prophesying war, others the result of the harvest. The 

 inhabitants of the Silesian mountains predicted luck, whenever the Army-worm took its way 

 down the valley, but unfruiti'ulness whenever it crawled up. The people in the Thuringian 

 woods predicted peace when it took the former direction, and war when it took the latter. 

 Some even believed their own destiny to be connected with the worm. They threw clothes 

 and ribbons in its way, and felt happy, especially hopeful women, when it crawled over the 

 things ; but they regarded one as a dead man whose things it avoided. 



These funny beliefs are now all overthrown by the studies and close observations which 

 Mr. Beling, an inspector of the German forests, has made of the Army-worm. He detected its 

 exact nature and origin, and he has delivered many treatises on the subject since the year 

 1868. His observations fully convinced him that the only cause for the appearance of the 

 Army-worm is the longing for food of larvse of the Sciara militaris. The Army- worm gener- 

 ally measures fifteen feet in length, and three to four inches in width. 



Though really not belonging to the Diptera, but, like the Cnethocampa processionea, to 

 the Lepidoptera, we may undertake here, for sake of conformity, to treat the AMERICAN 

 ARMY- WORM. The caterpillars forming it are termed Leucania extranea. They collect, like 

 the European Army-worm, in vast numbers, and devastate whole meadows in a short time. 

 When they can no longer find grass, they emigrate to other fields, and 

 attack even rye and wheat. Large clusters of these caterpillars have 

 been observed in the Western States and on Long Island. In 1861, such 

 a gathering of caterpillars proceeded fully sixty yards in two hours. 



The Texas and Mexican collections of the same or of a similar spe- 

 cies of caterpillars are known by the name of WIRE- WORM. 



THE accompanying illustration represents the common BREEZE- 

 GAD-FLY (Femaie).-:raia- FLY, a well-known example of the Tabanidae. It is also known by the 

 ^t^Tze.r head ' POP"!*" 1 names of GAD-FLY and CLEG. As in the gnats, the females are 

 the only bloodsuckers, but they exert their sanguinary ability with 

 terrible force. While staying in forests and suffering greatly from the bites of the Gad-flies, 

 I used to keep a little naphtha in a bottle, and rub it occasionally over my face and hands, for 



