1 1 6 The Irish Naturalist . May, 



They frequently appear suddenly in large numbers, in 

 water previously free from them, thus giving rise to many 

 popular and fallacious theories as to their origin. For 

 instance, it is said that horse-hairs, thrown into water, 

 change into these worms ; or that there has been a rain of 

 worms. The real explanation of this phenomenon is supplied 

 by the study of their life-histor}-. They spend the earlier, and 

 in point of time, the main portion of their existence, as para- 

 sites in the bodies of various animals, insects being specially 

 favoured ; but the larval stages have also been found in 

 spiders, Crustacea, fishes, frogs, &c., and I have frequently 

 noted the presence of the very young larvae in the bodies of 

 small aquatic Oligochaetes. On reaching a certain stage of 

 development; the larval Gordii leave the body of the host, 

 and as the individuals of a species, living in individuals of a 

 certain host-species all reach this stage at the same time, the 

 sudden appearance of these w^orms in large numbers in 

 accounted for. 



In the National Museum there is exhibited a specimen of 

 Parachordodes violacens, our commonest Irish Goi'dius, emero:- 

 ing from its host, the beetle Silpha sitbroiiuidata. The mature 

 Gordius does not feed during its short period of freedom, 

 and the mouth and alimentary canal become atrophied. The 

 male is easily distinguished from the female by its forked tail. 

 The eggs are laid in strings/ round water- weeds, and the 

 young larva, on emerging from the ^%<g^ is provided with 

 various spines by means of which it bores its w^ay into the 

 body of its first host, which is usually the larva of an insect. 

 The latter is eaten b\' the second host, in whose body the 

 larval Gordius completes a further stage of development, at 

 the end of which it emerges as the free-living form. 



The small collection sent to Prof. Camerano included two 

 species — 



Parachordodes violaceus (Baird), 



which has already been recorded from Great Britain and 

 Ireland.^ It appears to be the most prevalent species in this 

 country. The list of localities comprises Killaloe, Co. Clare; 

 Clonbrock, Co. Galway ; Swords and Lamba\^ Co. Dublin ; 



Vide R. Southeru, Irish Naturalist^ I907> P- 84. 



