96 Psyche [June 



nerve, or ocellus but is sufficiently good to show the relations of 

 the various parts. 



It would appear to be true that in the grasshopper the nerve of 

 the median ocellus is primarily a single nerve bundle. In other 

 insects, notably Hymenoptera, it has been shown that the nerve 

 supply of the single median ocellus arises as two strands which 

 later fuse,^ (Viallanes,* Janet) and ends in the single sensory cup. 

 In such cases each half of the median ocellar nerve arises as a 

 branch of the nerve of the lateral ocellus of the corresponding side. 

 In Bombus, where in an immature stage the median ocellus is elon- 

 gated laterally or even slightly constricted to form a lobate ocel- 

 lus, it is likely that at that period the tw^o nerve branches supply- 

 ing it are practically distinct throughout. 



The question arises whether the occurrence of two median ocelli 

 should be considered as a reversion to some ancestral type, or 

 should be looked upon as a variation having other significance. 

 The fact that a tendency to a doubling of the ocellus is apjDarent 

 in the pupal stage of Hymenoptera but later disappears in the 

 adult might lend support to the former view\ However, as, so 

 far as is known to the writer, no normal examples of a double me- 

 dian ocellus occur in lower insects, it would seem that the case in 

 Bombus should be explained in some other way — possibly as merely 

 the mechanical result due to the double origin of the nerve and 

 the crowded condition of the organs of the head in bees. 



In the case of the abnormal doubling of the ocellus in the grass- 

 hopper it would seem to the writer that the explanation probably 

 lies in some unusual influencing factor during its embrj^ological 

 period. 



The Second Ij^terxatioxal Coxgress of Extomology. 



Since the preliminary notice which appeared in Psyche for Feb- 

 ruary, the date of meeting for the congress at Oxford has been 

 changed. 



The meetings will extend from the fifth to the tenth of August, 

 1912, and a large and distinguished attendance is expected. 



5 Viallanes, H. Le Cerveau de la Guepe (Vespo crabro et vulgaris) Ann. Soc. Nat. Zool. 

 1887 7'' Ser. II, pp. 5-100, 6 pi. 



Janet, Chas. Anatomie de la Tete du Lasius niger, Limoges, 1905. 



