REPORT OF THE ENTOMOLOGIST AND BOTANIST. 239 



penetrate through the delicate skin at the joints of the legs of aquatic insects and live for 

 .some time inclosed within a cell inside the bodies of these. The next stage is as parasites in 

 tish, the food of which consists largely of aquatic insects. When the latter containing young 

 Plair-worms are eaten, the cells are broken or dissolved by the process of dige-^tion j.nd the 

 young worms at once work their way, by means of special hooks around the head (Fig. 9.), 

 into the stomach of the fish, where they again become encysted in the mucous layer. 

 After a time they bore through their cells and are 

 passed out from the fish's stomach into the water. ^' 

 Subsi quent to this, nothing is known, until tliey are ^':k" 

 found as parasites inside insects of various orders, and 

 it is ditiicult to conceive how it is possible for these 1^ 

 worms to enter the bodies of such active insects as ''^ 

 locusts and crickets, which also, besides, live mostly in 

 dry places. It is true, though, as has been pointed out, 

 that ground beetles, spiders and locusts which live in 

 low, moist places are most infested. Certain it is, how- Fig. 9.— Young Hair-worms after 

 ever, that Hair-worms are parasites inside the bodies of escaping from the egg, highly mag- 

 , 1 . i_ . • ' 1 XI nihed, showmg the circles of hook- 



aiany insects, and that specimens nave been seen to lay lets (p) drawn in, and (q) partially 

 eggs from which young emerged which passed through and (r) wholly protruded, 

 the stages described above. These worms are of two kinds, which, when only examined 

 superficially, differ chiefly in colour : dark ones, from 6 inches to a foot in length and 

 with a diameter not reaching at the thickest part one twenty-fifth of an inch, belonging 

 to the genus Gordius, with the above life history ; and others, white in cdlour, mucli 

 longer and slenderer, belonging to the genus Alennis^ which, although ."similar in their 

 parasitic habits to the Gordius worms, have a quite different mode of development, as 

 well as a difierent internal structure. Both kinds of these parasitic worms are frequently 

 found associated within the body of the same host. The eggs of Mermis are laid in the 

 ground and the young on hatching resemble their parents in form. On emerging from 

 the egg they make their way to the surface of the ground and enter at once on their 

 parasitic life in some insect. They acquire full growth inside their host and then bore 

 out through the skin and bury themselves in the ground. It is not until this period in 

 their lives that the genital organs develop. They pass the winter in the ground at 

 varying depths, and eggs are laid in the spring. I received from Mr. T. Pearson, of 

 Knowlton, Que., gardener to the Hon. Sydney Fisher, a large specimen 17 inches in 

 length, which he had found in December under a stone six inches beneath the surface 

 of the ground. 



As stated above, these parasitic worms infest insects of various orders. Mr. W. 

 Hague Harrington, of Ottawa, vvrites to me: — " I have frequently obtained Gordius 

 from locusts, and on one occasion I obtained two small specimens of Mermis from a 

 lady-bird (Hippodamia 13-punctata). 



In the First Report of the United States Entomological Commission is a full account 

 by Prof. Riley of almost all that has been found out concerning these strange creatures. 

 I quote the following : — 



" These Hair-worms are not only very frequently found in dififerent locusts, but Prof. 

 Leidy even has one from a cockroach. They likewise occur in many other insects ar.d 

 small animals, as beetles, moths and butterflies, bees, two-winged flies, spiders and snails. 

 As a rule, the worms forsake Lepidoptera while these are in the larva state or more 

 rarely in the pupa state, whereas they generally issue from Coleoptera and Orthoptera 

 only after these have acquired the perfect state." 



While they are inside the bodies of their hosts. Hair-worms are folded and coiled 

 up so as to occupy a surprisingly small space. When seen, as is frequently the case, on 

 the ground, they move in a snake-like manner, sometimes with a part of the body raised 

 up and swaying from side to side. When in the water, they are either knotted together 

 and tangled like a piece of black cotton or swimming with an undulated motion close to 

 the surface of the water. 



When referred to in correspondence, it is seldom that species of Gordius a,nd Mermis 

 are separated, though they are frequently mentioned. In no year do I remember so 

 many inquiries to have been made as during the past summer, which, of course, was due 



