AN INVASION OF BRITISH GUIANA BY LOCUSTS. 351 



the 1st and 2nd pairs are heavily spotted with this colour, and the femora of the 

 3rd pair show the black very distinctly, the tibiae and tarsi being almost wholly 



Fig. 4. Second stage nymph 



black. The ventral surface is yellow-brown with many black spots, and there 

 is a distinct white ventral margin to the abdominal areas. 



Length .' 11 -a mm. 



Length of hind femora . . . . . . 8"0 mm. 



No. of segments of antennae . . . . 17 



Third Nym-phal Stage. — The general appearance of this stage is like the preceding 

 one. The front of the head is not so black, in fact it is a brownish colour, while 

 the abdomen shows considerably more white. The pronotum too has become lighter 

 on the lateral areas. The antennae are still black. The distal portion of the hind 

 tibiae and the first two joints of the hind tarsi have also become lighter, being now 



Fig. 5. Third stage nymph. 



only marked with black. The ventral surface is spotted with black and now shows 

 a median white stripe. On the whole the insect is noticeably lighter in colour 

 than the previous stage. The wing-pads appear in this stage for the first time. 



Length . . . . . . . . . . 14 '7 mm. 



Length of hind femora . . . . . . 10"0 mm. 



No. of segments of antennae . . . . 20 



Casting of the third Nymphal Exuviae. — Ecdysis was only observed in one instance, 

 and in this case the nymph failed to free itself of the exuviae. The process, however, 

 will be described. 



When first observed (3.15 p.m.) the operation was already in progress and the 

 body was almost half withdrawn. The exuviae were ruptured mid-dorsally, and the 



