OLDEST KNOWN INSECT-LARVA. 433 



in any fossil insect, no matter how highly irregular its surface may have been in life), the 

 head is provided with lateral bosses, which may be partly explained as due to the under- 

 lying appendages; for when these supposed appendages are thrust forward and form the 

 anterior lateral lobes, it is these lobes which are embossed, as described in my previous 

 paper; while when, as in fig. 10, they are supposed to lie outside the lateral limits of the 

 head, the protuberances are still found connected with them. What appendages these 

 lobes may represent it would be difficult to say. One would more naturally expect such 

 evidently corneous organs, forming bosses even where they are separated from the head, 

 to be mandibles, but their broad and rounded shape gives no clear evidence of their use 

 in such a way; and in such a flattened larva it could not be supposed that they formed 

 a vertical fang, the crushing of which, from above downward, would bring all the ehiti- 

 nous portion together in a mass, and so produce a boss upon the stone. 



The three thoracic segments are almost invariably larger, generally considerably 

 broader than the others, and are often distinctly differentiated as a separate region, both 

 by their breadth, greater than that of the uniform segment behind, as well as by the 

 slight forward inclination of their sides. This appears clearly in fig. 5, but is generally 

 less marked than there by the smallness of the hindmost thoracic segment, which is not 

 often broader than the following abdominal segment, as in figs. 5 and 14. Usually also 

 the middle thoracic is larger than the front thoracic segment, so that their relative size is 

 II, I, III (see figs. 1, 11, 12, 14) but not infrequently the front one is the largest, as in 

 figs. 5, 6, 10, and there are some cases where the broadest part of the body is behind the 

 thoracic segments, and the order of breadth in the thoracic segments is III, II, I. In 

 these cases, as in figs. 4, 7, 13 and particularly 9, the whole aspect of the insect is changed, 

 and yet a careful study of the specimens leads one to the conviction that all belong to a 

 single species. In some, of which fig. 5 may lie taken as an extreme type, we are re- 

 minded, in form, of the larva of a longicorn beetle, while the other extreme, as in fig. 9, 

 recalls rather some of the Silphi'dae. What maybe looked upon as the average or normal 

 thoracic segment, is about three times as broad as long, subquadrate, with very slightly 

 concave front margin, and a little more distinctly convex hind margin, the sides well 

 rounded and the hinder angles more broadly rounded oil' than the front lateral angles, 

 giving a slight sublimate form to the entire segment. These segments are further 

 marked by more or less distinct lateral marks, usually impressed, either angular (figs. 

 5, 14) or rounded (figs. 1, 10, lo). which are the only indications, if such they are, of 

 appendages. 1 had thought they might be taken for the marks of very short legs, and 

 perhaps they can; but the figures given by Schiodte of the larvae of the coleopterous gen- 

 era Necrophorus, Anisotoma and Agathidium, where similar marks are purely sculptural, 

 leave me in doubt. Every one must have seen in nature similar marks on longicorn 

 larvae, but these are more generally mesially disposed, and do not, as here, reach so dis- 

 tant a point from the middle line. Whatever they are. there is nothing else on a single 

 specimen examined by me — many hundreds in number — which could be referred to 

 legs. 



The abdominal segments invariably taper to some extent toward the tail ; sometimes 

 the tapering is scarcely visible 'on the anterior segments, and it is always more pro- 

 nounced posteriorly, but here as before there are nearly all shades of difference between 



