230 i March, 



on the heads of Plantago maritima ; TJirips ulicis, in flowers of Ulex europseus, 

 Crocus susianus, and corn ; Thr. phalerata, on Lathyrus pratensis ; Thr. obscura, 

 common on wheat ; Tlir. ulmifoliorum, on leaves of elm ; Thr. atrata, in flowers of 

 Convolvulus soldanella, Dianthus, Centaurea cyan us, Campanula ; Thr. vulgatissima, 

 in all kinds of garden flowers, especially narcissi, umbelliferse, and plenty in flowers of 

 Sinapis nigra ; Thr. conorrhodi, common in flowers of wild roses ; Thr. glosmlaricB, 

 in flowers of gooseberry ; Thr. physapus, in flowers of Cichoracese ; Thr.fuscipennis 

 on Rumex ; Thr. ericce, on heath ; Thr. urticce, in flowers of Nasturtium, Thalictrum, 

 Ranunculus ; Thr. corymbiferarum, in flowers of Corymbiferse ; Thr. minutissima, 

 in Umbelliferse ; Thr. discolor, in flowers of Crucifera? ; Thr. livida, in flowers of 

 Ulex europasus ; Thr. primula, in flowers of primrose ; Thr. dispar, on Festuca fluitans 

 and other grasses ; Thr. brevicornis, on Festuca fluitans ; Thr. subaptera on Plantago 

 maritima ; Thr. juniper ina, on Juniperus ; Thr. rariegata, on flax ; Thr. phalerata, 

 in flowers of Vicia sativa ; Thr. atrata, on Spergula nodosa ; Thr. persicce, on 

 diseased leaves of peach ; Belothrips acuminata, prob., in flowers of Galium verum, 

 Lathyrus pratensis or Plantago on sand-hills by the sea ; 31elanthrips obesa, in 

 flowers of Sinapis nigra, Reseda, and Ranunculus ; Coleothrips fasciata, in flowers of 

 Reseda. 



I shall be much obliged for any favour which maj be kindly conferred 

 upon me, and shall be most happy, if I should be able, to assist in return. — Thomas 

 Pekgande, 321, D Street, S.W., Washington (D.C.), U.S.A. : January, 1882. 



[Possibly this request mav bring to the front some at present unknown student 

 of British Thysanoptera. — Eds.] 



Measurements in descriptive Entomology. — Under this title my friend, Mr. 

 McLachlan, suggests (p. 205 ante) that British "descriptive Entomologists" should 

 agree to adopt millimetres as the measure for insects ; and for this course, two chief 

 reasons are adduced. First, that some use the English inch as their unit instead of 

 the Paris inch ; and, second, that the millimetre is better than either. Now, I have 

 nothing to say in defence of those who have employed the English inch, except only 

 when they have written coram populo, for those to whom the Paris inch would be a 

 myth, because the Paris inch with its divisions into 12 lines was the accepted 

 standard, as Burmeister has shown. But I know two Englismen, at any rate, and 

 there are doubtless more, who have always used the Paris line in their descriptions, 

 and never a word has been heard about any insufficiency. And such lines are suffi- 

 cient, because the minuter dimensions of millimetres are misleading, even with 

 respect to insects of comparatively small dimensions, for this reason, that absolute 

 exactness in the stature of the individuals of a species does not exist, and line- 

 measurement is amply sufficient to express the average size and range of variation of 

 any ordinary insect. Any thing less than half a line in length is microscopic, and 

 for such objects microscopic measurements must confessedly be adopted ; these are 

 equally beyond lines or millimetres. But to give in millimetres the dimensions of a 

 butterfly which is several inches in expanse, or of a Goliath beetle or other enormous 

 insect, the individuals of the species, moreover, varying extremely in size, is about 

 as reasonable as always to quote large money-value in centimes. So that there is 

 really no advantage to any one in using millimetres instead of the Parish inch or 

 lines, well known throughout the scientific world, — and this is all I contend for, 

 whether the insects be large or small. 



