DRILUS DRIMYS. 



3-29 



of this machine, take them, as it were, by surprise, 

 when they think themselves safe. De Geer says it 

 is very difficult for other insects to elude their attacks, 

 and that he has even seen them devour very small 

 fishes. As these animals are found in almost every 

 ditch, you will doubtless lose no time in examining 

 for yourself an instance of so singular a construction." 



The formation of this organ varies slightly in the 

 different species, but the same general structure is 

 observable through the whole of them. 



The observation of De Geer, quoted above, upon 

 the motions of these larvae and pupae, arises in some 

 respect from another remarkable peculiarity exhibited 

 by them, consisting of an instrument which serves for 

 progression, although more immediately connected 

 with the office of respiration. These insects have, at 

 the extremity of the body, an aperture serving for 

 the entry of a certain quantity of water, which there 

 undergoes a process by which the air contained in it 

 is rendered serviceable for respiration. The orifice 

 of this aperture is defended by five scaly pieces, 

 forming a kind of tail, and which are opened or shut 

 together at the will of the animal. When, therefore, 

 a supply of water has been taken into the cavity, 

 these external pieces are closed, and other internal 

 organs brought into action, for the purpose of extract- 

 ing the vital principle therefrom ; and when this has 

 been effected, the external pieces are suddenly thrown 

 open, and the internal fluid discharged with violence, 

 a sudden forward jerk being thereby given to the 

 body of the insect. 



These insects live in the water ten or eleven 

 months preceding their final change, during which 

 period they change their skins several times. From 

 the middle of spring to the commencement of autumn, 

 the LibellulcE arrive at their perfect state. The 

 nymphs or pupae, ready to become winged insects, 

 are known readily by their larger size, and by the 

 iigure of their wing-covers, which become detached 

 from each other. They now quit the water, and 

 ascend the stems of any aquatic plant, so as to allow 

 their outer covering to dry and become brittle. 

 Some are ready to quit their old covering in the 

 course of two or three hours ; others are so much as 

 an entire day before this takes place. After this 



A, the dragon-fly making its exit from the pupa. B, the sam 

 drying its wings. 



process has taken place, the pupa attaches itself to ; 

 twig by means of its legs. Internal movements ar< 

 now perceived, and the skin splits down the back 

 the slit gradually increasing in size, until a sufficien 

 orifice is made to allow the head and legs to b< 

 drawn out, the head being thrown backwards, and th 



erminal abdominal segments still remaining in the 



)upa skin, serving to support the insect. After 



emaining some time in this position, it again raises 



ts head and body, seizes the stern of the plant with 



ts fore legs, and draws out the remainder of the 



abdomen. In this position it remains a considerable 



pace of time, until its wings, which hang downwards 



and which, at first, are not larger than the cases by 



vhich they were covered), acquire their full size and 



beautiful gauze-like appearance. At the end of a 



couple of hours the insect is able to support itself in 



he air on the wing. 



There are numerous species of dragon-flies, of 

 which many are natives of this country. Some of 

 them, forming the modern restricted genus Libcllula, 

 are remarkable for the diversity of colour in the 

 opposite sexes, the abdomen in the males being of a 

 jeautiful blue, and that of the female yellow. The 

 argest species of the group found in England is the 

 Anax imperator, a noble species, a solitary specimen 

 f which we observed, during several weeks, hovering 

 over the same little pond on Wimbledon Common, 

 Surrey, during the present summer. 



DRILUS (Olivier). A genus of coleopterous in- 

 sects, belonging to the section Pentamera, sub-section 

 Serricornes, and family Lampyrida;, having the an- 

 tennas remote at the base, the head not narrowed in 

 front into a snout, and the eyes of ordinary size in 

 both sexes. The females are, however, destitute of 

 wings, and their antennas are but slightly serrated, 

 whereas those of the males are very strongly pecti- 

 nated. The mandibles are slender and acute at the 

 tips, with a tooth near the extremity. 



The genus is composed of but a few small species, 

 of which the males only, until very recently, were 

 known. Naturalists were also ignorant of their me- 

 tamorphoses. We are indebted to the Count Meil- 

 zinsky for the first account of the femalo, and the 

 transformations of the genus, which, as well as the 

 economy of the species, are very curious. The larva 

 is about three quarters of an inch long, and is found 

 in the interior of the shell of the common snail (Helix 

 ncmoralis of Linnaeus), upon (he inhabitant of which 

 it feeds. When full grown (about the month of 

 September), it remains for some time in an inactive 

 state, during which period it was regarded by M. 

 Meilzinsky to be in the state of the pupa. The 

 observations of M. Desmarest proved such not to 

 be the case. The latter author also ascertained, that, 

 having remained in this inactive state until the month 

 of May, the larva is transformed into a real pupa, in 

 whiclTstate it continues perfectly inactive, unless when 

 touched, when a drop of yellowish fluid is exuded 

 from the sides of the body. M. Meilzinsky, not being 

 aware of the connection of this insect with the well- 

 known Drilus Jlavescens, regarded it as a distinct 

 genus, to which he gave the name of Cochlcoctonus 

 vorax, establishing the genus upon the peculiarities 

 observable in the large and unwieldy females, which 

 are destitute of wings and wing-covers, like the 

 "low-worm, and which nothing but direct observa- 

 tion would induce any one to regard as the other sex 

 of the small and pretty drilus. M. Desmarest, how- 

 ever, assisted by his pupils, succeeded in rearing the 

 apterous females from M. Meilzinsky's pupae, and 

 not only observed the coupling of the cochleoctonus 

 and drflus, but also found, within one of the snail 

 shells, the exuvias of the male drilus, and which were 

 easily recognisable from the peculiar construction of 



