GEOMETERS. 



187 



The MOTH appears on the wing in July, and 

 occurs in England, Scotland, and Ireland 

 (The scientific name is Cidaria immanata.) 



Obs.Mr. Hellins, whose observations 

 have at different times thrown so much light 

 on the life-history of our native Lepidoptera, 

 has turned his attention to the difficult task 

 of distinguishing between this closely allied 

 pair of species. His first paper, treating of 

 the perfect insects, is published in the 

 Zoologist ; his second paper, treating of the 

 preparatory states, appears in the Entomolo- 

 gist's Monthly Magazine. 



I have freely availed myself of both these 

 papers, and still more freely of my friend Mr. 

 Doubleday's assistance, to whom Mr. Hellins 

 fully acknowledges his obligation for much of 

 the information he has given to the public. 

 From these sources, far more than from my 

 own observations, the following summary 

 results. First The time of appearance in 

 the perfect state differs : C. russata appears 

 in May, and again in August, the May 

 moths being the parents of the August moths. 

 C. immanata appears in July : thus the 

 single brood of C. immanata is intermediate 

 between the two broods of C. russata. C. 

 russata certainly hybernates in the caterpillar 

 state, but C. immanata passes the winter in 

 the egg state. Secondly The habit of the 

 moths differs : C. russata has the habit of a 

 true Geometer, when at rest with its wings 

 deflexed ; C. immanata rather resembles a 

 Deltoid : and this difference arises from a 

 difference in structure, the fore wings of 

 C. immanata being slightly narrower and 

 perhaps also slightly more pointed. Thirdly 

 The colour and markings : both species vary 

 greatly in colour, especially as regards the 

 disk of the fore wings, the extremes being 

 dark smoky, almost black, and pale cinereous, 

 almost white ; but C. russata has a very com- 

 mon variety in which the disk is fulvous : C. 

 immanata has no such variety. Again, C. 

 immanata has the two narrow, waved, and 

 angulated, transverse, sienna-brown bars on 

 the fore wings, much more distinct than C. 

 russata. Moreover, there is a difference in 

 ihe exterior outline of the broad central band 



of the fore wings : "In both species this com 

 mences at the costa, at about two-thirds of 

 the distance between the base and the tip, 

 and runs across the wing for a little space with 

 very small teeth, then shoots out into a large 

 bilobed (sometimes, in C. russata, trilobed) 

 tooth, which is followed by another not quite 

 half as large ; and, lastly, slants away to the 

 inner margin, forming three more teeth not 

 much differing in size ; but the distinction is 

 this, that in C. immanata these teeth, espe- 

 cially the largest of them, are more prominent 

 and acute ; in C. russata they are not so pro- 

 minent and often rounded." Fourthly The 

 caterpillar of C. russata is dull ochreous at 

 first, but afterwards brightish green, and often 

 ornamented with red on the sides. The cater- 

 pillar of C. immanata is bright yellow at first, 

 but afterwards dull green, and never orna- 

 mented with red on the sides. Mr. Hellins 

 also says that the anal points are acute in 

 C. russata, obtuse in C. immanata. I have 

 described both caterpillars from nature with- 

 out observing this, but have added these 

 words in inverted commas, as quoted from 

 Mr He tins. 



o57. THE WATER CARPET. The palpi are 

 /ery snort, never visible from above as more 

 than two minute points projecting between 

 the eyes ; the antennae are simple in both 

 sexes ; the fore wings are ample and rather 

 pointed at the tip ; their colour is brown of 

 two shades ; the dark shade is confined to a 

 basal blotch, a broad median band, a costal 

 blotch near the tip, and a vague hind-marginal 

 band ; the basal blotch and median band have 

 white marginal lines ; the band includes a 

 narrow transverse discoidal spot, and the 

 hind-marginal band includes a transverse 

 series of white spots. An oblique elbowed 

 white line runs from the extreme tip through 

 the hind-marginal band, towards the middle 

 of the wing : the hind wings are brownish- 

 gray, and all the wings have a marginal 

 series of black spots : the head, thorax, and 

 body are dark brown. 



Two book species are here included which 

 I call varieties. 



