122 LEPIDOPTERA OF MIDLOTHIAX. 



investigate. The fact that chrysAlides occasionally pass one or two successive 

 winters in a torpid state, until a warm, or at least a favourable, season 

 developes the perfect insect, is quite insufficient to explain the phenomenon. 



Four years ago Spcelotis 7'avida, S. augur, and S. pyrophila, were abundant 

 in my own garden, as was also Polia advena, Aglossa pingidnalis, Alucita 

 polydactyla, all of which have since been extremely scarce, and during the 

 past year, although looked for, altogether wanting. In like manner, a few years 

 ago, (1846,) Sphitix convolvidi, was very abundant throughout the country, 

 though far from being a common insect either before or since that time. This 

 sort of periodicity in the appearance and non-appearance of insects in particular 

 seasons, is an interesting and important subject to investigate; and is an 

 additional reason, if one were wanting, for keeping exact registers, not merely 

 of the rarer insects, but' of the commonest and most abundant kinds. Why, 

 for example, Plutella Cruclfe"arum should in general be a common insect, and 

 has in the past year suddenly become, by its swarms, a destructive pest, I am 

 quite unable to determine; but how greatly would the value of Entomology 

 be enhanced, could we with certainty predict the prevalence of a particular 

 insect, and thus enable the farmer to meet the attacks of his small but often 

 most destructive enemy. 



For reasons I have already alluded to it will not be supposed that in 

 presenting this list, Mr. Logan or myself do so in the idea that it affords 

 a perfect catalogue for the shire of Edinburgh. A life-time of observation 

 would not insure this, as every year brings to light species which are either 

 altogether new, or were only believed to be met with in the more genial climate 

 of England. We have indeed delayed the publication of this list during the 

 last two years owing to the numerous additions we have found it necessary to 

 make, and it is now only the feeling that no length of time will enable us 

 to comprise all the insects which may be found in this neighbourhood, that 

 we have determined no longer to delay. As it is, it is the result of many 

 years careful observation; and for its accuracy we feel we have little to fear 

 from future in^stigations. Perhaps we have been a little hastened in our 

 intentions to publish this list by the appearance of Mr. Gray's interesting 

 catalogue of the Lepidopterous insects of the adjoining districts; we observe 

 however, that although his observations comprise a far wider range of country 

 than our own, the number of species noticed is far loss. I almost regret that 

 our district had not comprised the circuit of ten miles around Edinburgh, 

 rather than the mere arbitrary boundary of Midlothian; we have been 

 debarred, for example, from including many interesting species in our catalogue 

 taken at Burnt Island, and the opposite coast, as well as at Guillane Links, 

 by the aiTangement we have made, and to which when once determined upon, 

 we made it a point strictly to adhere. The frequent reference made to 

 '^Duddingston and Arthur's Seat" by Mr. Logan, and "Balgreen and Cor- 

 storphine Hill" by myself, will be sufficiently explained by the circumstance 

 that the two districts thus frequently alluded to form our respective places 



