GALL-FLIES. 107 



Tricolor, Hart., males and females of -which appear in July from 

 a white hairy gall on the upper side of the leaves. 



Again, Biorhiza Eenum, Hart., is a uniform reddish-brown wing- 

 less parthenogenetic female, which emerges in mid-winter from a 

 small kidney-shaped gall on the under side of the oak leaves, 

 which has ripened and fallen to the ground in October. After this 

 female has laid her eggs, the results are round juicy galls, varying 

 from the size of a pea to that of a cherry, and placed on the bark 

 of the oak, but always arising from a small bud. These arrive at 

 perfection in May and June, and give rise to a brood of black flies, 

 with yellowish-red legs and abdomen, with very long wings, and 

 consistina; of both males and females. 



Family \l.— Chalddidce. 



Ovipositor generally exserted ; antennse elbowed (basal joint 

 often very long) ; six- to thirteen- jointed (rarely fourteen) ; palpi 

 short ; wings with very few veins ; pupa naked ; habits parasitic 

 (with a few exceptions). 



The Chalddidce include a great number of small insects, few of 

 even the larger species of which exceed half an inch in expanse. 

 Many of them are singular in shape, and others brilliantly metallic ; 

 but, owing to their small size, they have hitherto been studied by 

 comparatively few entomologists. Perhaps about 1200 or 1500 

 species have hitherto been described ; but much still remains to be 

 done, especially in foreign countries, before we know much of so 

 extensive a group. 



In the comparatively large species of Leucnspis, Smlcra, Chalcis, 

 etc., the hind femora are of a very peculiar shape, being so much 

 thickened as in some cases to resemble the abdomen in size. On 

 the under surface these thickened femora are either serrated or 

 armed with strong, and sometimes large and pointed, teeth. 



The genus Leucospis, Fabr., includes black species with yellow 

 spots, remarkable for the position of the ovipositor of the female, 

 which is recurved over the abdomen as far forwards as the scutellum; 

 they are not British. In the genus Halticella, Spin., the long scape 

 of the antennae is placed just above the mouth, instead of near the 

 top of the head, as in most other insects. Callimome, Spin., 

 includes a number of small brilliant green or bronzy species, with 

 long ovipositors, which are mostly parasitic on galls. Euchctrls, 

 Latr., and some other genera h?vp, beautifully branching antennae. 



