13(3 Mr. T. V. Wollaston on certain Coleojrfcrous Insects 



that Atlantic group. Their main difference consists in the structure 

 of their tarsi, the first and second joints of which (instead of being 

 simple) are very broad, and deeply bilobed, — except in the hinder 

 pair of the male sex, where only the basal one is thus developed. 

 Moreover, as regards these hinder male feet, there may also be a 

 difference in the actual number of the articulations (as compared 

 with those of Europs) ; but unfortunately the structure is so obscure, 

 even beneath the highest powers of the microscope, that I am unable 

 to decide whether there are one or two minute joints concealed 

 within the lobes of the basal one. If there should be but one, then 

 the posterior male tarsi will be only trimerous, and therefore dimi- 

 nished in the number of their joints ; but if two, they will be 

 tetramerous (like the remainder of the feet in both sexes), their 

 form only being altered, — i. e. the second articulation (which in the 

 other feet is as large and cordate as the first) will be reduced to an 

 excessively minute size, like the penultimate one in all the feet. At 

 any rate, whether the number of the hinder tarsal joints of the male 

 feet be the same or not, m Mimema and Europs [and I may add that 

 it is nearly equally difficult to pronounce for certain whether they 

 are trimerous or tetramerous even in the latter also], the form of the 

 tarsi is unquestionably different, — the two largely-developed bilobed 

 basal joints in all the feet of Mimema except the posterior ones of 

 the male sex, where (whatever be the exact number of the following 

 minute articulations) the basal one only is thus constituted, giving 

 it a character which it is impossible to mistake. 



Moreover, this tarsal peculiarity is not altogether unaccompanied 

 with minor differences (from Europs) even in its oral organs ; for in 

 Mimema the antenna? have their third joint a little longer than the 

 fourth (thus making a slight approach to Rhyzophagxis), and the 

 two divisions of their club are more compact, or less separated from 

 each other ; also the outer maxillary lobe, although narrow like that 

 of Europs, is not so aciculated, but almost palpiform, — appearing as 

 though articulated at its base, and with its long apical portion sub- 

 clavate. The ligula also of Mimema, although elongate and linear 

 as in Europs, is sharp and angular at its apex (between the palpi), 

 instead of being obtusely rounded, and with broad elongate mem- 

 branous internally ciliated paraglossae stretching out on either side 

 from the anterior angles. The general aspect of both groups is that 

 of Rhyzophagus ; but, apart from the many other differences which 

 will be gathered from the diagnoses, I may add that, whilst in the 

 latter the numerical formula for the tarsal joints is 5-5-5 and 5-5-4 

 in the two sexes respectively, that for Mimema (and indeed for 



