APHIS. 



APHTHA. 



The mode of generation of these insects is 

 curious and interesting. Each family in 

 spring and summer consists of wingless in- 

 dividuals and pupae ; all of these are, how- 

 ever, females. The males are not born until 

 the end of the summer or autumn. They 

 fecundate the last generation produced by 

 the previously-born specimens, consisting of 

 wingless females, which then deposit fecun- 

 dated eggs, which remain through the winter, 

 and produce young in the spring capable of 

 reproduction without fresh impregnation. 

 Eleven generations have been known to be 

 produced .thus, without fresh impregnation. 

 According to Dr. Burnett, the members of a 

 third generation can be seen within the bodies 

 of the parents. 



Many of these insects are covered with a 

 mealy matter, or with cottony threads se- 

 creted by the body. 



These insects are of great interest, on ac- 

 count of the destruction they cause in agri- 

 cultural crops : as instances, we may mention 

 the hop-fly (A. humuli], the bean-dolphin 

 (A.faba), the turnip-fly (A. brassica), &c. 

 The Aphis rosce is a very common one, and 

 may be found upon most rose-buds. Apple- 

 blight is also probably produced by a species 

 of Aphis. 



BIBL,. Westwood, Introduction, &c. ; 

 Walckenaer, Hist. d. Insect es; Burnett, Sil- 

 liman's Journal, 1854, xvii. pp. 62, 261; 

 Walker, Ann. Nat. Hist. 2nd ser. i. ii. iii. 

 iv.&c. (1848-49, &c.) 



APHIS, L. A genus of Insects, of the 

 family Aphidae. 



Char. Abdomen bicorniculate ; antennae 

 long, setaceous ; fore wings with three ob- 

 lique discoidal nerves, the first trifid; pro- 

 boscis short, collar long. 



The species are very numerous. See 

 APHID^B. 



APHRODITA, L. A genus of Annulata. 

 One species of this genus (A. aculeata) is 

 well known as the sea-mouse, and is com- 

 monly found on the sea-coast, and always 

 admired on account of the splendid iridescent 

 colours reflected from its spines and bristly 

 hairs. Its body is from 3 to 5 inches long, 

 H broad, and oval; the back of an earthy 

 colour. The head is small, entirely concealed, 

 with two round clear spots, or eyes, on the 

 vertex. The hairs and bristles run down 

 each side of the body ; the back is roughish, 

 with a thick felt of hair and membrane form- 

 ing a kind of skin. When this coat is cut 

 through, fifteen nearly circular plates or scales 

 (elytra) are found on each side, which partly 



cover each other, and the middle of which 

 are the largest. If two of the plates lying 

 next each other be separated, we then see 

 upon the intermediate ring small tubercles 

 divided by a pit, furnished behind with pec- 

 tinate appendages, the gills or branchiae. 



Antennae minute, palpi large, subulate, 

 jointed at the base. Mouth with a large re- 

 tractile edentulous proboscis ; the orifice en- 

 circled with a short, even, thick-set fringe of 

 compound penicillate filaments divided into 

 two sets by a fissure on each side. Thirty- 

 nine pairs of feet; biramous; the upper 

 branch carries the long, flexible, brilliantly 

 coloured bristles forming the silky fringe on 

 each side of the body. 



This animal is a very interesting object to 

 the microscopist, as its tissues are very trans- 

 parent and easily examined. 



The brilliant colours of the bristles and 

 hairs arise from iridescence, produced by a 

 number of longitudinal striae or interspaces 

 between the component fibres of which the 

 bristles and hairs consist ; they also exhibit 

 transverse splits or cracks; they are not 

 materially changed by the action of boiling 

 solution of potash, except that the external 

 coat of the hairs becomes transversely wrin- 

 kled, giving these the appearance of being sur- 

 rounded by a number of fibres (PI. 40. fig. 

 20). 



BIBL. Johnston, Ann. Nat. Hist. 1839, 

 430; Van d. Hoeven, ZooL, p. 232. 



APHTHA. A disease affecting the mu- 

 cous membrane of the mouth, tongue, &c. 

 It exhibits itself in the form of rounded 

 patches of larger or smaller size, of a whitish 

 or yellowish colour, One form of it, vulgarly 

 called the " thrush," and in French muguet, 

 which occurs very frequently in children, and 

 in adults towards the fatal termination of 

 chronic diseases, is of special interest to the 

 microscopist, inasmuch as the patches con- 

 sist of numerous epithelial scales mixed with 

 filaments and isolated cells of a fungus. A 

 portion examined under the microscope 

 exhibits, 1, numerous oval cells (a), PL 30. 

 fig. 1, rarely containing an internal globule 

 or nucleus ; 2, long filaments (6) exhibiting 

 a further advanced stage of development ; 

 the filaments are but rarely jointed ; 3, epi- 

 thelial scales, sometimes perfect (d), but 

 usually wrinkled and otherwise altered in 

 form, and frequently more or less opake (e), 

 so as to be hardly recognizable except when 

 treated with potash; intermingled with these 

 bodies are sometimes vibriones or bacteria 

 (Bact. termo, /) and a molecular form of 



