4 SPECIFIC DISTINCTIONS. 



but they are smaller, and the abdomen especially is 

 shorter and differently shaped. The sexual forms are 

 more active and fly about more than do the agamic. 



From the sexual females the agamic differ fre- 

 quently in many particulars. Generally they are larger 

 and more bulky in shape ; there is often a difference 

 in coloration ; the autumn form may be wingless, the 

 spring winged, or, as in B. terminalis, the spring brood 

 may sometimes be wingless as well as the autumnal. 

 The agamic generation, again, live longer than the 

 other. Sometimes there is a difference in the palpi, 

 as in the autumn form of Biorhiza megaptera having 

 four joints in the maxillary and two in the labial, 

 while the spring brood has one joint more in both. 

 More remarkable still, there may be a difference in the 

 oral apparatus in the larvas. 



The difference in the form of the ovipositor is very 

 marked — a difference not only in size, but in form: 

 in the spring generation it may be short, with the 

 boring apparatus straight and not much longer or even 

 shorter than the ovipositor itself; while in the other 

 brood it may be much larger and longer, with the 

 borer curved round it. 



As a whole the gall-making Cynipidas are larger 

 than the parasitic. Black is a prominent colour for 

 their bodies, but many are brown, fulvous, or yellow, 

 and a few reddish. 



The specific distinctions are often very obscure ; 

 indeed, in not a few instances the flies cannot be 

 separated at all; e.g. Andricus albopunctatus, A. calli- 

 doma, A. Malpighi, A. 4-lineatus, &c, and many species 

 of Gynips. In those cases the only trustworthy 

 criterion of specific distinctness is furnished by the 

 galls. Colour may occasionally afford a good character 

 — e.g. Trigonaspis megaptera, but in others it is quite 

 worthless. The structure and number of joints in the 

 antennas, the form of the wing- cells, the sculpture of 

 the thorax, and to a certain extent the clothing of the 

 body, the length of the parapsidal furrows, and the 



