130 



Vetpa ; and on this, with some other facts, Ratzeburg founded the remark- 

 able, though untenable, theory that the head of the imago was the first and 

 second segments of the larva combined. In reality, the rapidly developing head 

 leaves its previously too small quarters, and finds room by pressing backwards 

 the other parts beneath the effete skin ; and having done so, the various parts of 

 the head, and first of all the eyes, begin to show themselves as development 

 proceeds. In most insects this is a process involving several days ; and the dis- 

 tortion caused by the head taking up its new position is very evident long before 

 any trace of eyes is visible ; nor is any change observable until after the 

 larva has done feeding. Having examined a full-fed larva of Rkipiphorus, I ob- 

 served, as usual, those eye-spot3 placed well back in the second segment. But 

 I was much surprised, on examining a larva that was still feeding, to observe 

 the eye-spots within the head of the larva, showing that the eyes of the imago 

 were beginning to develope, both before the larva had done feeding and before 

 the imaginal head had assumed its larger dimensions. These eye-spots consisted 

 of a patch of little brown pigment- points — one for each facet of the perfect eye. 



The young external larva (Figs. R. I.) is semitransparent, with none of the 

 masses of white fat th.it obscure the interior of the full-grown larva, and 

 render it white and opaque. Each of the first five segments after the head, 

 presents two large dorsal prominences, one on each side ; and the tracheal sys- 

 tem and intestine can be easily made out. The latter is a large simple sac, 

 pale yellow in colour, with numerous circular markings and rounded dots, and 

 is in continual rhythmic movement. The tracheal system is very like that 

 of other Coleopterous larva? ; it is probably the same in the full-grown larva, as 

 the positions of the spiracles are the same. From the first to the second spiracle 

 the lateral trunk is double ; and about its middle is a short branch, the abor- 

 tive second thoracic spiracle : the only difference from the Coleopterous type 

 is that there is no spiracle in the twelfth segment ; but there is a distinct short 

 tracheal trunk running towards the skin to represent it. 



The full-grown larva (Figs. L. and 8, and 9) has a very close superficial 

 resemblance to a Crahro or Pemphredon larva. It is 11 millims. in length (this 

 is from the fourth to the twelfth segment) ; from the jaws to the last seg- 

 ment it is dorsally 21 millims. , but ventrally 8 millims. ; its lateral diameter 

 is 4J millims, its antero-posterior 2A millims. It is therefore much flattened ; 

 and this flattening is chiefly in front. The head (Figs. 10, 11) is very small, 

 and curved forwards so as to be almost out of sight, the front of the head 

 being directed rather towards the body of the insect than directly downwards. 

 It possesses a pair of triangular jaws (Figs. 12 and 13), produced at the apex 

 into an extremely sharp point. There is a transverse line beneath these ; and 

 there are eminences, that may be called labrum, maxillie, and labium ; but I 

 cannot determine the actual mouth-opening or any other apparatus, except that 

 a to-and-fro sucking-movement is observable among the contents of the head. 

 The second segment is rather large, and possesses dorsally a large trefoil 

 boss on either side ; it is in the front part of this that the eye-spots are 



