D Y T I C I D JR. 



habits and transformations have been recorded. The 

 eggs of the D. marginalii, according to Rcesel, are 

 hatched ten or twelve days after they are deposited. 

 Ju tour or five days, the larva is nearly half an inch 

 long, when it sheds its skin for the first time. A 

 second moult takes place in about the same time, 

 when the insect has attained twice its former size : 

 when full-grown it is about two inches long. In sum- 

 mer fifteen days is sufficient for it to attain this size, 

 and to pass into the pupa state, and in fifteen or 

 twenty more days the perfect insect is produced. 

 Those larvae are found in all waters, and when the 

 period of their transformation to the pupa state is 

 arrived, they bury themselves in tne earth at the 

 margin of the water in which they are produced, and 

 form an oval cell, in which they are transformed to 

 inactive pupae. 



The mouth of the voracious larvae is not constructed 

 in the same manner as that of the larvae of most 

 coleopterous insects ; instead of the mandibles being 

 short and fixed near together, they are placed at the 

 sides of the front of the head, being very long, slender, 

 curved, and acute at the tips, having a channel along 

 its surface with a terminal orifice, these hooks are 

 struck into the body of the prey of the larva, and by 

 their assistance it is enabled to suck those fluids for 

 it.s own support. The respiration of these larvae is 

 effected by an apparatus placed at the extremity of 

 the body, so that in general it is to be perceived sus- 

 pended at the surface of the water by means of two 

 hirsute filaments at the tail, between which the two 

 breathing spiracles are to be seen ; hence, when the 

 larva rises to the surface of the water, these spiracles 

 are immediately brought into contact with the air, 

 aud the ciliae of these appendages quickly drying, 

 serve as a buoy to retain the larva in this situation, 

 which, however, it is enabled instantly to quit by 

 giving to its body a vermicular motion, and beating 

 the water with its posterior part, the fringe of which 

 serves as an oar. When the larva is full grown, it 

 creeps out of the water, and Lyonnet at this period 

 observed that it possessed the ordinary number ol 

 spiracles along the sides of the body, which, of course 

 could not have been previously employed (the animal 

 breathing by its tail as before stated), but which are 

 given to the animal to be employed when it has 

 quitted the water to become a jnipa. Lyonnet satis- 

 factorily demonstrated that this was the fact by again 

 placing in the water one of those larvae, when bubbles 

 of air escaped from each of the breathing pores, a 

 circumstance which had not previously taken place. 



^ft** 



A, the larva. B, the perfect Dyticus marginalia. 



The period of coupling of these insects is during 

 the winter and spring months, after which the female 

 according to Lyonnet, deposits eggs more than once 

 each laying consisting of from forty to fifty eggs 



hey are deposited without any care in the water 

 ingly, the period of oviposition lasting several days, 

 idea of the form of the larva and prrlV-ct insect 

 will be more readily obtained from the figures which 

 ve here give of them than from a detailed description. 

 The similarity of circumstances in which these 

 nsects are placed renders it necessary that they 

 hould exhibit but little variation in structure. The 

 lumber of species is but small, but they are dispersed 

 over a wide extent of country. For instance, a . 

 arge species of Cybislcr (of which genus, with one 

 exception, the species are extra-European) is found 

 Tom Senegal to New Holland, being observed at 

 [}uinea, the Cape of Good Hope, Madagascar, 

 Mauritius, and the Indian Archipelago. The species 

 of the genus Dyticus seem exclusively to inhabit 

 Europe and the north of America^ of which latter 

 country the productions in many respects closely 

 approximate those of Europe. 



The sexes of these insects exhibit various pecu- 

 liarities. The elytra of the males are smooth and 

 finely punctured ; whereas those of the females, in 

 many of the larger species, have several deep furrows, 

 which are covered with a coating of hairs. The 

 males in some of the latter species have the three 

 basal joints of the tarsi of the fore Iro-s very broad, 

 dilated, convex above, and furnished below with tine 

 hairs. By means of this instrument the male retains 

 its situation during coupling. In the perfect insect 

 the respiratory apparatus does not differ from that of 

 other beetles ; but, in order to bring the spiracles into 

 contact with the air, the beetle is obliged from time 

 to time to ascend to the surface of the water, which is 

 easily effected by discontinuing the motions of the 

 feet, when the body, which is lighter than the water, 

 immediately ascends to the surface. In this situation, 

 with the head downwards, and the legs stretched out 

 at right angles, the extremity of the body is pushed 

 above the surface of the water, the elytra are slightly 

 raised at the tips from the upper surface of the 

 abdomen, and a sufficient supply of air is introduced 

 beneath the elytra, which are then closed. If the 

 insects wish to remain beneath the surface of the 

 water with their legs unemployed, they are compelled 

 to lay hold of aquatic plants with their tarsi. 



Since the time of Linnaeus, numerous generic divi- 

 sions have been separated from the Linmvun genus ; 

 that of Haliplus, distinguished by several remarkable 

 peculiarities, having been first established by Latreille, 

 Clairvillc, Leach, and other entomologists, have added 

 to their number. The genera of which the family is 

 at present composed are, Hullphis, Cnemviotux, Pcch- 

 bius, Anisomcra, Hyphydntx, Hygrotits, Hydro? writs, 

 2fotcrus, Hydrocatit/tus, Coplotomus, LaccoplUus.Aga- 

 bus, Colymbctes (with numerous subgenera), Cifbittcr, 

 Actfutff Hydalicus, Dyticus, Lcionotus, and Eunectes ; 

 the majority of which comprise species inhabitants of 

 this country. 



The typical genus, Dyticus, as now restricted, com- 

 prises the largest species in the family, the anterior 

 tarsi of which are dilated in the males, the elytra of 

 the females furrowed ; the posterior tibias are of 

 moderate size, and the claws didactyle. There are 

 eight or nine British species, of which the most 

 abundant is the Dyticus margitialis of Linnaeus, of an 

 oli ve- black colour ; the margins of the thorax and 

 elytra ochreous, with an obscure lunula of yellow 

 near the extremity of the latter. It varies from one 

 to seventeen inches in length. 



