108 BRITISH BEETLES. 



containing eggs, which she carries attached to her ab- 

 domen, and from which, in about ten days, the larvae 

 are disclosed; in a few hours another sac being formed. 

 This insect is now supposed to be extinct in England, 

 formerly occurring at Whittlesea Mere. It appears to 

 be rare on the Continent, in spite of the fertility of the 

 female. It lives in stagnant water, at the roots of 

 aquatic plants. 



In Helophorus and its allies the tarsi are not natato- 

 rial, and have the first joint very short and often scarcely 

 distinct from the second. Some of them are slightly 

 metallic, and most of the species live close to the water, 

 among stones, etc. ; one or two, however, often occur in 

 dry places (H. rugosus, Plate VII, Fig. 4) . The Hydrance 

 and their allies, in which the last joint of the maxillary 

 palpi is shorter than the penultimate, frequent stones 

 half immersed in the water or the water-line of muddy 

 banks; the species of the remaining genera living ab- 

 solutely in the water. One of these, Hydrous piceus, 

 often seen in aquaria, and known as the "harmless 

 water- beetle," is perhaps the largest British beetle ; the 

 female makes a paper-like, pear-shaped sac, containing 

 eggs, which is fixed on some aquatic plants at the 

 surface of the water. The larva is, when full grown, 

 extremely long and stout, of a leathery texture, wrinkled 

 transversely, and dirty-brown in colour ; the head is 

 horny, flat on the upper side, and with strong projecting 

 sharp mandibles; the legs are short, and the body con- 

 tracts behind, having two openings at the extremity of 

 the last segment, being the terminations of two great 

 lateral tracheal tubes, through which the insect breathes. 

 These larvae are very voracious, feeding on other insects, 

 etc. ; they swim well, bending themselves into an arch, 



