Decatoma is a genus proposed by Spinola, but I am ignorant 

 of his characters : from the typical Eurytoma it is distinguished 

 by the antennae being clavate in the female ; and the 2nd basal 

 joint is very nearly as long as the 3rd, not reckoning the little 

 rings ; whereas in Eurytoma, the 3rd joint is frequently almost 

 as long as the basal one, and very much longer than the 2nd. 

 It is very important to remember, also, that the maxillary palpi 

 are only triarticulate ; for Mr. Haliday has observed, that they 

 are composed of 4 joints in E. longula ? Dal. 



I shall characterize the species lent to me by F. Walker, Esq. 

 of Southgate, where they were taken, I believe, on grass under 

 trees. 



1. D. Cooperi Curtis' s Brit. Ent. pi. 34^5. fern. 



For males of this pretty insect, I am indebted to A. Cooper, 

 Esq., who beat them out of a hazel-bush, with one female, in 

 September, close to the river Mole at Cobham. 



2. D. biguttata Swed. — Fejnale much smaller, but similar to 



No. 1 : antennae black, the tip of the 2nd joint only 

 ochreous : face variegated with yellow : collar of the 

 same colour, with a large trilobed black mark : abdo- 

 men with a yellow spot on each side, near the centre : 

 legs pale ochre, variegated as in No. 1. 



3. D. variegata Walk. MSS.—SimWsiV to No. 2, but much 



smaller : the collar is yellow, with the centre and a 

 spot on each side black, a yellow horse-shoe-formed 

 mark above each upper wing : the hinder thighs have 

 only a broad black ring round the middle, and the 

 stigma is trigonate. 



4. D. obscura Walk. — Female similar to No. 3, but the collar 



is almost entirely black : there is no yellow spot on the 

 side of the abdomen, as in No. 2 and 3 ; the hind thighs 

 and tibiag are black, except the knees : stigma sublu- 

 nulate, pale fuscous, black at the costa. 



5. D. unicolor Walk. — Male much smaller: antennae pale to- 



wards the apex : stigma small, black : tarsi and knees 

 of hinder legs alone yellowish, the former fuscous at 

 the apex. 



6. D. minuta Walk. — Male similar to No. 5, but the face is 



variegated with ochre : there is an ochreous ring ou 

 each side the collar, and the tibiae are ochreous, ex- 

 cepting the middle of the posterior pair, which is black. 



7. D. mellea Walk. — Male as large as No. 2, ochreous : collar 



and head yellowish, both a little blackish at the base : 

 scutellum variegated with black, and three large con- 

 nected black spots on the back of the abdomen. 

 S. D.?penetransJv/V.— Brassy-black: abdomen bluish-black, 

 compressed : apex truncated : aculeus subexserted. — 

 Linn. Jrans. 5. 109.pl. 4./ 10, IJ. 

 This minute insect is probably allied to the present group. 

 Corylus Avellana (Hazel-nut Tree), in flower, accompanies 

 the insect. 



