INSECTA MADERENSIA. 131 



least, that the sexes have been correctly determmed. Nevertheless, if snch be 

 true, the ordinary law of development would seem in one respect to be departed 

 from, the tubercles being frequently more particularly enlarged in i\iQ females : at 

 any rate this is so uninistakeably carried out in a single instance* that the fact 

 ought not to remain unnoticed. The whole of the members have a tendency to 

 be more or less covered with a scaly substance resembling dii-t, and which at times 

 so completely enveloijes them as nearly to conceal even the brighter portions of 

 the spotted forms. They are, likewise, as regards at all events their elytra, more 

 or less wriukled and rugulose, — although (considering the T. Lcmri as a specific 

 centre from which most of the others appear as it were to radiate) it wUl be per- 

 ceived that a few indeed become comparatively smooth, — even whilst the greater 

 number recede so manifestly in the opposite dii'ection that they become at length 

 almost difficult to characterize from the accumulation of protuberances, ridges, 

 granules, and setae with which they are beset. The sculptiu'e of their heads and 

 prothoraces (the latter particularly) is exceedingly anomalous, and constitutes in 

 fact a significant item even in theii' generic diagnosis. Thus, our fu'st Lmj)ression, 

 on examining one of the outer limits of its variations, would probably be that it 

 was widely and oj)enly reticulose : nevertheless a closer inspection (especially of 

 the subcu'cularity of the " reticulations," and of how they gradually contract, and 

 become, during the process, more and more elevated) would at once explain the 

 nature of the structure, which may be pronounced, under all circumstances, to be 

 granulate. "WTien thus enunciated, the successive modifications are easily in- 

 telligible, — the extreme state in one direction being that in which the pustules 

 are so closely set, broad, and flattened as to cause the surface to appear reticu- 

 lated; whilst that in which they have diminished so far in breadth as to leave 

 spaces between them, and have become proportionably more upraised and acute, 

 is the ultra condition in the other. The former of these obtains in that section of 

 the genus which I have assumed (for Madeu*a) to be normal, whereas the latter is 

 indicative of those members which are al:)errant. In Sicily however, where the 

 only representative which has hitherto been discovered occiu-s, it is not imj)ossible 

 that the second of these states may prevail, since the T. gibbulus of that island has 

 the granules comparatively minute and few, and with a more decided appearance 

 of being truly isolated and distinct than in any of the species mth which we are 

 here concerned. "V^liilst the insects are at rest their antennae recline backwards 

 beneath the dilated edges of their prothorax, which, although not channeled, is 

 concave, or slightly hollowed out, on the under side in order to receive them. In 

 the Sicilian T. gibbulus, this cavity, owing partially to the excessive prominence of 

 its pronotmn which causes the sides to descend like a roof, is remarkably evident, 

 ■ — nevertheless even there it can scarcely be considered grooved, as described by 

 Erichson. I have observed that several of the species (as, for instance, the T. ro- 

 tundatus, nodosus, and cicatricosus) are liable to be affected with an extremely 



* T. nodosus. 



s2 



