'panmles in Nest of Bonibus dcrhamellus. 113 



lation is not seen in fig. 3 b. The lower articulation is 

 brought about by the large condyle (fig. 3 b, co.) fitting 

 with a point on the margin of the epicranial plate (post- 

 gena ? : see fig. 2 b).* 



The apex of the mandible is divided into 2 teeth, and 

 there is also, along the upper (dorsal) edge of the apical 

 portion, a series of 4 other teeth, that furthest from the 

 apex being very small. Molar portion of the mandible 

 large (fig. 3 b, fn.p.), its inner surface {i. e. towards the 

 middle line) raised into three blunt teeth (indicated in 

 fig. 3 b, but in mandibles remainiiig in situ in the head, 

 which lie in a slightly different plai\e, they appear nmch 

 more marked). The molar part also bears a number of 

 transverse series of very minute elevations ; in fig. 3 b 

 they are only shown on its ventral surface, but actually 

 they extend round on to the dorsal side. 



Between the apical and molar parts is a comphcated 

 set of structures, difficult to represent in fig. 3 b, as they 

 lie one behind the other in several focal planes. Viewed 

 from the ventral side there is towards the apex a thin 

 transparent lamina with rounded outline, its margin set 

 with long, sharj), prominences; this lamina is extended 

 into another thin; transj)arent, broadly lanceolate part 

 (fig. 3 B, I.) lying just in front of the molar jwrtion of the 

 mandible. Dorsal to the rounded lamina (seen partly 

 through and behind it in fig. 3 b) is a number of stout, 

 pigmented, finger-like processes, which appear to be 

 grouped in several series, each at right angles to the plane 

 of the figure. Below these, and between the rounded 

 and lanceolate laminae, is a dense group of spines and 

 bristles of differing length and thickness, and seen through 

 the transparent lanceolate lamina is a series of sharp- 

 pointed structures resembling long saw-teeth. The dotted 

 line between the transparent laminae and the main body 

 of the mandible in fig. 3 b represents the fairly clearly 

 defined line at which the chitin becomes very thin and 

 colourless. Possibly the whole of this complex structure 

 corresponds to th()se parts or appendages, .of very different 

 forms, which have been described in the mandibles of a 



* The words " upper " and " lower " are used here with reference 

 to the aetual position of tlicse points in the larva. According to 

 Couistock and Koilii (6, pp. 14, o7) tlio u])per articuhition is, from 

 a strictly niotpholo^ical point of view, really ventral, and tho 

 lower really pleural. 



TRANS. ENT. SOC. LONl). 1920. — PARTS I, II. (jULY) I 



