42 



jackets {Vespa occidentalis, Cr.) were entering the tents. For some time it was supposed 

 that the object of the new-comers was to forage for sugar and other camp supplies. But 

 before night it was noticed that the numbers of flies in the tents had been perceptibly 

 reduced, and on the second morning it was discovered that the wasps were intent on 

 the acceptable task of removing our troublesome guests. There were generally as many 

 as forty or fifty wasps in each tent at once, and each wasp was observed on leaving the 

 tent to be carrying out the body of a fly, not for burial, nor as food for its captors, but 

 for storage in the nests of the wasps, and undoubtedly as food for their young. Each 

 captured fly, before removal from the tents, was deprived of its wings and legs, and on 

 several mornings we were awakened from our slumbers by these severed members drop- 

 ping upon our faces. The wasps were unremitting in their labors from daylight to 

 dusk, and in four or five days the flies had ceased to be troublesome by their numbers, 

 the wasps having gained upon them almost as rapidly as they entered the tents.- Oc- 

 casionally a specimen of Vespa maculata (Linn.) was observed co-operating with V. occi- 

 dentalis, Cr., in the removal of the flies." 



Although flies are able to live for several months, but a small percentage of them sur- 

 vive to die of pure old age. Dangers imperil their existence at every stage; a great propor- 

 tion of the eggs, pup® and larvae are devoured by other insects, birds and fowls, or destroyed 

 by floods and droughts ; while such as reach maturity find spiders, birds, poisons, traps and 

 deadly enemies on every side, to thin their ranks, so that of all the mighty armies of Sum- 

 mer, barely a corporal's guard survives until the Winter. Late in the autumn the strag- 

 glers are seen, dingy and draggled, feebly crawling about the walls, and all unlike the trim, 

 active insects that danced on tireless wing in the summer sunbeams. Some even man- 

 age to survive the winter, by hybernating in crevices, and come forth on the approach 

 of spring, looking still more worn and decrepit, to continue the race. 



One enemy which attacks them in their old age must be specially mentioned, as its 

 effects often aroiase some curiosity in those who observe them. In the autumn many 

 dead bodies of flies, still in the attitudes of life, are seen adhering to the mirrors, cur- 

 tains and other articles in our rooms. On closer inspection a small cloudy spot will be 

 seen to surround each, and the abdomen to be much distended, with broad whitish 

 zones separating the segments. 



A touch of the finger makes the body crumble into dust ; the whole of its contents 

 having been consumed by the fungus which is the cause of these appearances. This 

 " fungus is a species of the genus Seprolegnia, formerly called Sporondonema, Empusa, 

 or Achlya. It consists of short jointed threads, two or five millimeters long, growing 

 from the bodies of flies usually in autumn. These threads enlarge in the outer end or 

 last joint, which becomes filled with swarm spores, that, as soon as mature, burst their 

 envelope, move about for a few hours, then come to rest, generally near the parent fila- 

 ment, and immediately begin to grow. 



The reason that the fly remains standing where he dies is that, as the fungus con- 

 sumes his internal organs, he becomes too enfeebled to overcome the adhesion of his 

 feet to his last resting place, and the viscid exudation from the filaments of the pulvilli 

 harden and cement them so firmly to the spot, that even after death " the fly sticks to 

 the wall." 



