Mr. Smith on Trypoxylon. 57 



XVI. Observations on the Sphex figulus of Linnceus ; (Try- 

 poxylon figulus, Za^r.,i^«Z>.,^"c.); awt/oMer Hymenoptera. 

 By F. Smith, Esq. 



[Read 5tli July, 1847.] 



Trypoxylon figulus, previous to the year 1835, was generally con- 

 sidered to be a parasitic insect, about which period Mr. Johnson 

 detected it conveying a species of Aphis into its nest, as recorded 

 in Mr. Shuckard's Monograph on the British Fossores. I had 

 myself certainly considered it to be parasitic, and its habit of 

 frequenting old posts, dry sand banks, &c., constantly prying 

 into every hole it meets with, strengthened my opinion. Subse- 

 quent observation shows how careful naturalists ought to be in 

 forming conclusions, derived either from partial observation, or 

 founded upon immaterial structural differences. 



In the month of June, 1845, I met with a complete colony of 

 Trypoxylon, formed in a dry sandbank ; their numbers were truly 

 astonishing, the insect being usually solitary in its habits. On the 

 top of the bank was a close hawthorn hedge, an admirable situa- 

 tion in which to find its prey, generally consisting of spiders. It 

 was quite amusing to observe the rapidity with which they captured 

 and conveyed their prey. 



Last summer, I observed several females busy about an old 

 decayed post. One I detected burrowing with great assiduity ; 

 others were conveying their prey, which in this instance consisted 

 of Aphides. I dug out several of the masses of Aphides, on some 

 of which a small larva was feeding, and on another I detected an 

 egg, which was hatched in four days. It grew rapidly, and in 

 ten days it had consumed the whole of its stock of food, the legs 

 and wings alone remaining. It then remained in a state of lethargy 

 from three to four days, when it commenced spinning its cocoon ; 

 this occupied three or four days more. The cocoons are oblong, 

 a little rounded at each end, and their length varies from four to 

 six or seven lines ; in texture they exactly resemble the semi- 

 transparent French tracing-paper. Having spun the cocoon, the 

 larva remains in a state of lethargy until the following spring, 

 when at the end of April it casts offa larva skin, becomes a pupa, 

 and then gradually assumes the perfect state ; the head becoming- 

 first visible, then the wings, and afterwards the legs present them- 

 selves ; it is then of a pale amber colour, which gradually becomes 

 darker and darker, until it changes to jet black. A few warm 



