SECONDARY SEXUAL CHARACTERS, 21 



Hemichroa alni the ? has the head and thorax for 

 the greater part red and the legs black, while the 

 cj has the head and thorax black and the legs 

 testaceous. On the other hand, there are species which 

 have the males lighter coloured than the females. 

 This is the case with Nematus rumicis, Heptamelus 

 ochroleucus, Tenth-redo zonata, T. velox, 8fc. 



2. The eyes. The most noteworthy difference in the 

 eyes is with the <? of Alia, in which they are con- 

 fluent, or nearly so, at the top of the head, although in 

 the normal position with the ? . 



3. Month organs. In Cimbex, Trichiosoma, and 

 especially Clavellaria, the mandibles in the male are 

 very largely developed, projecting, and strongly 

 toothed. 



4. Differences in the structure of the legs. In 

 Trichiosoma the hind femora are grooved on the lower 

 side, each end of the groove at the apex terminating in 

 a blunt tooth. In Gimbex the patellae are well deve- 

 loped, and at the base of the basal one there is a pro- 

 jecting spine. In the same genus there are blunt, 

 short spines on the coxae, which are themselves very 

 large, and projecting. Some species of Allantus and 

 Tenth-redo have the legs in the rf (especially the hinder 

 pair) much longer than in the ? , and the tarsi and 

 base of tibiae thickened, while in Tenthredo zonata, 

 besides these differences, the tarsi on the under side, 

 are provided with closely pressed velvety pads of hair. 



5. Antennce. With the majority of saw-flies, the 

 antennae merely differ in being a little longer or 

 thicker, or in having the joints more compressed. 

 But with the Lophyrina they are very dissimilar, being 

 either deeply biramose as in Lophyrus, or with only 

 one row of pectinations as in Monoctenus and Clado- 

 macra. The same is the case in a less degree with 

 Cladius. In Schizocera and other Hylotomina, they are 

 furcate or cleft in two, like the prongs of a fork, the 

 joints being either densely covered with long hair, as 

 in Sericocera, or bare and grooved as with Dielocera. 



