A GUIDE TO THE STUDY OF BRITISH WATERBUGS. 175 



Ilyocoris, like most waterbugs, is subject to the attacks of 

 watermites (family Hydrachnidae). After what d'Herculais terms 

 a "bizarre copulation," the eggs are laid in spring in incisions 

 in soft-stemmed aquatic plants, or on the under side of the 

 leaves. The young larva is pale red, six-legged, each leg com- 

 posed of six segments. These young larvse, upon hatching, 

 move about in the water, and fasten themselves, often in large 

 numbers, to different water insects by means of sharp hooks at 

 the end of the palpi. Once fixed, the head and mouth-parts 

 stretch until they become separated by a neck from the main 

 body^ the transparent skin of which rapidly swells and elongates 

 so as to form a bag, with the more solid dark-red parts visible 

 anteriorly. The elongated maxillae penetrate and extend beneath 

 the chitinous covering of the host until they form a long pointed 

 thread. The legs curl up, become useless, and are more or less 

 withdrawn. The larva gradually passes to the pupa state within 

 this bag, which becomes more and more swollen and rounded 

 posteriorly, and finally bursts to release the adult eight-legged 

 mite. These bag-like larvae were looked upon as the eggs of the 

 waterbugs by many old authors, and the bugs were likened to 

 the Surinam toad {Pij)a pipa (Linn.) ), that hatches its eggs on 

 the skin of its own back. The adult swims actively about in the 

 water, but before attaining maturity fixes to some plant, and 

 undergoes another moult without material change of form. On 

 the smaller aquatic bugs only three or four larvae are perhaps 

 seen, but on certain giant exotics a much greater number are 

 found, as many as five hundred having been counted on a single 

 specimen of Belostoma fluminea, Say. The commonest British 

 species appear to be Hydrachna geographica, Koch, the imago of 

 which is scarlet and black, and Hijdrochorcutcs globulus (Miill.), 

 a rich purple in the imago state. The American species men- 

 tioned above was described as Hydrachna belostomce, Biley ; 

 Mr. A. D. Michael examined for me some larval Hydrachnids on 

 a Sinhalese waterbug {Amorgius indica) about four years ago, 

 and considered them probably the same as the American form. 

 He concluded : " The watermites, when parasitic, do not usually 

 confine themselves to a single host, but are often found on 

 several species ; and the geographical distribution of Acari is 

 usually very wide, often astonishingly so." * 



embi'yology and anatomy of Ilyocoris (see " Beitriige zur Morphologie vind 

 Entwicklungsgeschichte der llhynchoten," 1899, in Nova Acta Leop. Carol. 

 Deutsch. Akad. Ixxiv. pp. 355-81, text-tigs, ii., and pi. xv. figs. 1, 4, 9, 

 pi. xvi. figs. 15-17, 21-22, pi. xvii. figs. 29. 



-•= Note by G. W. Kirkaldy in E. E. Green, "Biologic Notes on some 

 Ceyloncse Ehyncbota. — No. 1," 'Entomologist,' xxxiv. p. 116 (1901). See 

 also U.S. Entom. Commission, First Report (1878), p. 313; Kiinckel d'Her- 

 culais, " Les Insectes" in Brehm's ' Merveilles de la Nature,' ii. pp. 757-8 

 (1883) ; and Andrew Murray, ' Economic Entomology. Aptera,' pp. 151-2. 

 Mr. J. N. Halbert, of Diiblin, is studying tbe British Hydrachnidse, and 

 would be glad of material. 



