4 THE TROPHI MANDIBLES. 



intermediate joint. A few genera of Hylotomina have 

 the large apical joint deeply grooved. 



The number of joints varies : Cimbicides have from 

 five to seven ; Hylotoma has only three, namely, two 

 small ones at the base, and a very long terminal one. 

 Mne must be regarded as the normal number, that 

 being the number with Tenthredina (with a few 

 exceptions) and Nematina. The exceptions are the 

 Phyllotomides which have fewer joints (Goenoneura with 

 seven or eight) or more (Phyllotoma ten to sixteen 

 joints). Pinicola again has twelve- jointed antenna ; 

 LopTiyrus seventeen to twenty-three; and Lyda twenty- 

 two and upwards.* 



Male insects have the antennas often differently 

 shaped from those of the female ; being often hairy, 

 pectinated, &c., as explained further on. 



The mandibles. These are as a rule short and thick, 

 broad at the base, and tapering (sometimes bulging out 

 first) to a blunt point at the apex. In Hylotoma and 

 some Nematina there is only the apical tooth (PI. X, 

 fig. 10), but other genera have them toothed or in- 

 dented along the edge as well, and in some cases the 

 basal part has a jagged edge. This is more especially 

 the case with carnivorous species (Tenthredo, &c. 9 

 PL XII, figs. 13, 16), while again certain males 

 (Trichiosoma) have long, sharply-toothed mandibles, 

 which they use in fighting among themselves. 



The form of the maxilla (PL X, fig. 3) does not offer 

 any striking features, nor does it afford good cha- 

 racters which can be used in classification. The outer 

 lobe (PL X, fig. 3, 2) is more or less rounded at the 

 apex, and contracted in the middle, or quadrate at the 

 apex as in Allantus. The inner lobe (1. c.,) is very short 

 with Hylotoma, with which it scarcely projects beyond 

 the base of the outer ; in Lyda it is slightly longer ; 

 with Nematus it ends in a sharp point, which reaches 



* When the number of joints exceeds the normal number (9) they 

 tend to vary in the same species, so that the number of joints cannot 

 always by itself be regarded as a specific character. 



