MOOR MANAGEMENT 375 



As will be seen in chapter x., this portion of the investigation has 

 afTorded the Committee no little difficulty ; the small size of the worm, and 

 the fact that a great part of its existence is passed outside its host, have made 

 it difficult to follow this parasite through all its changes of form. 



The proverbial hunt for a needle in a bundle of hay is simplicity itself 

 compared to the labour of detecting the larval nematode (so small as to be 

 visible only under a high-power microscope) in an acre of heather. In addition 

 to the difficulties arising from the size of the worm, the search is made more 

 complicated by the presence of other free-living nematodes, very easily mistaken 

 for Trichostrongylus pergracilis. Some of these complete the whole cycle of 

 their life in the soil, and are never parasitic at all. 



With very few exceptions every Grouse has in its body a varying number 

 of Strongyle worms, of which the females are each capable of producing many 

 eggs ; these eggs pass from the body with the csecal deposit, and after 

 three days' incubation on the moor reach the larval stage. The csecal deposit 

 is well known to all field observers, and is readily distinguished from the hard 

 cartouche-shaped dropping of the main intestines by its light chocolate brown, 

 viscous appearance. 



The number of the larvae in a Grouse - dropping varies enormously, and 

 depends directly on the degree of infestment of the bird from which it comes ; 

 in the case of heavily infected birds they may be reckoned in tens of thousands. 



The larvse during the earlier stages of their existence appear to have the 

 power of lying dormant for an indefinite period, they are not affected by the 

 frost ; a rise of temperature will at any period raise them out of their torpid 

 condition ; excessive drought and perhaps the salt spray of the sea are the only- 

 conditions injurious to their health. 



After passing through the casting of skins common to most nematode worms, 

 and after a period generally to be reckoned in weeks, but probably never 

 less than ten days, the larvse assume a resistant sheath and become active 

 young nematodes ; they climb the shoots of the damp heather, and, like the 

 East Coast fever-tick on the South African spear-grass, lie in wait for an 

 opportunity to complete their life history by returning to their natural host — 

 incidentally their prey. 



Once the Strongyles have returned to their host the further stages of their 

 life history follow on in rapid succession. Absorbed with the heather shoot into 

 the crop, protected in the gizzard by the sheath-like covering from the action of 



