■^^^mimmifm^ 



by Max Morse in Science: "Complaints were made by re- 

 sidents along adjacent avenues of the numbers of these 

 'worms,' as they were called, which covered the side- 

 walks and terraces and even entered the residences. 

 Often in passing along the paths running in the campus 

 it was found to be difficult, if not impossible, to avoid 

 crushing numbers at every step." 



Millipede hordes are usually short-lived, but they 

 can be persistent, as the residents of Streamwood, a Chi- 

 cago suburb, discovered in 1962. The villagers tried 

 lime, muriatic acid, ammonia, DDT, various chemical 

 sprays, and even gasoline, with little effect against the 

 army. 



Most instances of hording are apparently one-time 

 events where they have been observed, but recurrences 

 | are known. Beginning in the spring of 1958 and continu- 

 ing every spring for several years thereafter, large 

 aggregations of millipedes appeared on a farm near 

 Paintsville, Kentucky, apparently feeding on rotting 

 vegetables and animal fodder. One year the horde was so 

 overwhelming that the farmer resorted to a propane 

 blowtorch to burn them from the walls of his house. 



Cedar Point, Ohio, now the site of an amusement 

 park, has also been the chosen spot for recurring aggrega- 



Photo made by Rainer Zangerl in 1959 of hording millipedes in Indiana's 

 Wabash Valley. Courtesy Rainer Zangerl. 



tions. In the early years of this century, Pleuroloma 

 hordes were observed there on several occasions. 



Moisture is one of the factors to consider in trying 

 to explain millipede hording. Frank Young found that 

 Pleuroloma flavipes moved more slowly under humid con- 

 ditions, aggregating in damper parts of the woodland 

 floor. Rainer Zangerl observed the same species 

 aggregating in particularly large numbers in a dry stream 

 bed — a relatively moist habitat. Many aggregations 

 appear to correlate with rainfall activity. A sighting in an 

 arid region of New Mexico was recorded during that re- 

 gion's rainy season. Periodic mass appearances in India 

 occur during the annual rains. In the Midwest, mil- 

 lipedes have been reported crawling up telephone poles 

 just before rainfall. Swarming before a rain has also been 

 observed in Louisiana. 



Additional factors may be the availability of pre- 

 ferred food and habitat. A number of invasions have 

 been reported in the east central states, where dense for- 

 ests, with abundant leaf litter and other organic mate- 

 rial, provide shelter, moisture, and food — an ideal 

 millipede habitat. 



Some specialists, including the noted English 

 biologist J.L. Cloudsley-Thompson, believe that 

 aggregating may be stimulated by a complex of environ- 

 mental factors, such as the effects of soil humidity and 

 texture on the hatching of millipede eggs. 



While the causes of hording remain elusive, there 

 are steps one can take to control them. Charles T 

 Behnke, Ohio Agricultural Cooperative Extension 

 agent, recommends the removal of organic material, 

 such as grass clippings, from areas near the house. Home 

 invasions may be prevented by such basic measures as 

 sealing basement doors and other openings. A variety of 

 insecticides are also now recommended. But since the 

 aggregations are usually short-lived, and millipedes pose 

 no physical threat to man, insecticides may not always 

 be warranted. 



A useful course of action, in any case, may be to 

 take photos of the horde, as Zangerl did, and collect a 

 number of specimens to pass on to a specialist. It may 

 also be productive to contact the specialist immediately, 

 so that he may have the opportunity to observe and 

 record this curious event. ¥M 



The authors are indebted to several colleagues for aid in preparing this 

 article: Rainer Zangerl allowed us to quote from his unpublished account of 

 his discovery of the mass aggregation in Parke County, Indiana. Richard L. 

 Miller, of the Ohio State Cooperative Extension Service, supplied us with 

 information about hording events at Streamwood, Illinois, and Paintsville, 

 Kentucky. Rowland M. Shelley, of the North Carolina State Museum of 

 Natural History, provided many helpful comments on an earlier draft, 

 substantially improving this article. 



iV^'Vi 4 • «.%'♦'-'/,„•« i\v.*<i » . iw, 



* W.V A A 



.tnA'j : a _ "» Wa*« 



" V*a* ♦* 



V*A»-#A 



.•*.« «, 



