172 



BRITISH MOTHS. 



coloured or violet, or purple-brown, and 

 sometimes absent ; the legs and claspers are 

 of the same colour as the body. 



The MOTH appears on the wing in June and 

 July ; is one of our very commonest species, 

 occurring in every field, land, and hedgerow 

 throughout the summer. (The scientific name 

 is Camptogramma bilineata.) 



MALE. FEMALE. 



339. The Gem (Camptogramma fluviata). 



339. THE GEM. The antennae are pecti- 

 nated in the male, the pectinations being very 

 short and inconspicuous. The male has the 

 fore wings clay-coloured, inclining to wains- 

 cot-brown, with a narrow transverse median 

 band of a smoky-brown, and including a 

 small black discoidal spot, which is surrounded 

 by a pale ring ; there is an oblique smoke- 

 coloured shade at the tip of the wing, descend- 

 ing towards its centre ; the clay -coloured area 

 on both sides of the median band is traversed 

 by faint white lines, the two more conspicuous 

 of which are between the band and the hind 

 margin ; the first of these is waved, the second 

 zigzag. The fore wings of the female are 

 purple-brown, sometimes inclining to brick- 

 dust-red ; the median band is faintly indicated, 

 but the discoidal spot is very conspicuous, 

 rendered so by the ring which surrounds it 

 being snowy-white : the hind wings in both 

 sexes are pale brownish-gray, with waved 

 lines both lighter and darker : in each sex 

 the head, thorax, and body are much the 

 same colour as the fore wings. 



I have found the CATERPILLAR of this 

 geometer on the leaves of the common persi- 

 caria (Polygonum persicaria), but I have not 

 1 escribed it from nature, as a very accurate 

 description which I have quoted below was 

 previously published in the " Entomologists' 

 ! utelligencer " for 1858 : " A lovely female of 

 this species laid me some EGGS on the 24th of 

 J uly ; they were oblong, flattish, and yellow, 

 but changed to a dusky-brown colour on the 



1st of August ; the following day the CATER- 

 PILLARS hatched ; at first, they were very 

 dingy, but on the 8th of August became dusky 

 sap-green, and on the 16th assumed their 

 characteristic markings.' There were evidently 

 two distinct varieties, one of which had the 

 ground colour of a greenish-gray, tinged with 

 red between the segments ; the spiracular line 

 blackish and irregularly interrupted ; the back 

 (except the last two segments) dusky, having 

 on the intermediate segments a row of five 

 elongated diamonds of the ground colour, with 

 a dusky dot in each ; on the front segments 

 these markings ran into three parallel dusky 

 lines, while on the end segments there were 

 four slender dusky lines arranged in a dia- 

 mond pattern ; the claspers had a dusky 

 stripe running down them. The other variety 

 had the ground colour of a light yellowish- 

 green, quite yellow between the segments; 

 the spiracular line and pattern on the back 

 faintly indicated by dusky-black lines and 

 dots. These caterpillars feed readily on 

 groundsel (Lenecio vulgaris), at last eating 

 through stems bigger than themselves ; but, 

 as their frass seemed very watery, I doubt 

 whether this is their proper food. They were 

 quiet in their habits, resting on the under 

 side of the leaves, hiding themselves skilfully, 

 and could not be easily dislodged ; when dis- 

 turbed, they curled up the front segments, 

 but not into such a twisted knot as I have 

 sometimes seen in more slender geometers. 

 From the 21st to the 23rd of August the 

 caterpillars, being full-sped, spun up in moss. 

 After having been in chrysalis about a fort- 

 night, the perfect insects emerged. There 

 went down two of the green and four of the 

 darker caterpillars ; there have come up 

 again one C. Jhtviata (male), and five C. 

 gemmaria (female) such a narrow risk did 

 I run of missing the solution of this problem. 

 Solved, however, it is, and C. fluviata and C. 

 gemmaria are hereby declared to be man and 

 wife. I expected to find the difference of 

 colour in the caterpillar would turn out to be 

 a sexual one ; this, however, has been contra- 

 dicted by the result. The CHRYSALIS is brown, 

 smooth, spiked at the tail, and enclosed in a 



