1844.] Linnean Society. 18? 



nuto : maxUlcs subiequaliter bilobfE ; palpi mediocres, 6-articulati, arti- 

 culis tribus basalibus iequaiibus, secundo tertioque crassis, quarto 

 paulo minore, quiiito omnium minimo quadrato, sexto gracili, baud 

 reliquis longiore : mentum sub-semiovatum ; palpi tuberculis promi- 

 nentibus affixi, breves, crassi, 4-articulati, articulo secundo latiore, 

 tertio omnium gracillimo longitudine primi: labium latum, trilobum. 



This genus is most nearly related to Schizocenis, Latr. The 

 s])ecies on which it is founded is named by Mr. Curtis Dielocerus 

 Ellisii, and is described at length, and the distinctions pointed out 

 between it and Hylotoma formosu, Klug, to which Mr. Curtis was 

 at first inclined to refer it. Its economy is totally different from 

 that of any other known species of Tenthredinida ; the caterpillars 

 of the solitary saw-flies, especially the larger species, forming single 

 oval cocoons of a very tough and leathery material attached to 

 twigs ; and those even of the gregarious species placing their co- 

 coons (which are oval cases of silk and gum) in an irregular manner 

 with no unity of design. The caterpillars of Dielocerus Ellisii, on 

 the contrary, which are evidently gregarious, unite to form on the 

 branch of a tree, an oval or elliptical case, four or five inches long, 

 narrowed superiorly, very uneven on its surface, and of a dirty 

 whitish ochre in colour. The cells, thirty-eight in number in the 

 nest examined, are placed at right angles to the branch, piled hori- 

 zontally one above the other, unequal in size and irregular in form, 

 those next the tree being pentagonal, the central ones hexagonal, 

 and some of the outer ones nearly round or oval. In one of these 

 cells Mr. Curtis found a dead female, and most of them had the 

 exuviae of the caterpillars remaining, but no shroud of the pupae ; 

 he thinks the smaller cells may have been occupied by the males. 

 At the end of each cell is a circular lid, formed of the same leathery 

 material as the rest of the comb, which being cut round by means of 

 the sharp mandibles, leaves an opening through which the saw-flies 

 make their way. In two of the cells were found the dead cater- 

 pillars, which closely resemble those of the genus Hylotoma. 



The author observes upon the dissimilarity of the mode of forma- 

 tion of this nest to that of any previously observed, the compound 

 nidus (as far as hitherto known) being always the work of the parent 

 insects for the protection of their young through the first three stages 

 of their existence. In this case, hov/ever, it is formed by the larvse 

 themselves for the purpose of their own metamorphosis. The nearest 

 approach to this economy seems to be the nidus formed by the mag- 

 gots of some of the Ichneumones adsciti, whose silken cells are placed 

 regularly in rows. 



