528 Mr. G. A. K. Marshall on 



neither its sharpness of outline nor, in a print prepared 

 from the negative, any of the detail of the surface. A 

 tendency in the same direction is manifest in £N.s fasci- 

 atijjeoinis (Fig. 5), but it is hardly noticeable in the repre- 

 sentation of the resting position in Fig. 4. Mr. Marshall 

 informs me that the Diplopteroiis appearance of Scolia 

 alaris is very marked daring life, both at rest and in 

 Hight. 



It is interesting to inquire for the possible reason of 

 this mimicry. Fabre (" Insect Life," translation, London, 

 1901, pp. 99, 100) states that the Fossores, using their 

 sting for hunting and providing food for the larvge, are 

 much less prone to employ it in defence than the 

 Diploptera, in which it has this latter meaning alone, and 

 not only so, but when used it is far less painl'ul in the 

 former than the latter. The FompilidcV, he considers, 

 produce the most painful effect, but far less than those 

 which follow from the sting of a bee. On the other hand, 

 my assistant, Mr. A. H. Hamm, who has had great experi- 

 ence of our British Aculeates, and always takes them out 

 of the net with his fingers, tlius gaining very exceptional 

 knowledge of their relative powers in this respect, does 

 not altogether share Fabre's opinion. He states that 

 while the common wasp, and of course the hornet, for his 

 experience includes even this insect, produce more pain 

 than any other British Aculeate (I leave the hive-bee out 

 of account), many of the Fossores produce more pain and 

 use their sting more readily than other Aculeates. At the 

 same time Mr, Hamra's treatment is one that the mildest 

 Aculeate may be expected to resent if its sting can pierce the 

 skin of the fingers, and the question is rather whether the 

 Diploptera are not recognized as more formidable than the 

 Fossores by the natural enemies of insects. It is very 

 probable that this is the case, the combined attack made 

 upon enemies incautiously disturbing a society being 

 one element in producing an increased respect for single 

 individuals of the same kind or with the same general 

 appearance. 



When an illustration of Scolia alaris was shown to the 

 Entomological Society on March 5, 1902, and this interpret- 

 ation suggested, Colonel Yerbury and Mr. Verrall pointed 

 out, at the close of the meeting, that similar opacity of the 

 costal area of the wing and transparency in other parts was 

 characteristic of many Diptera mimetic of Hymenoptera, 



