PHYSIOLOGY OF INSECTS. 117 



by means of a distinct and free joint instead of 

 a sutural fixed line : it has this form in the tiger- 

 beetles. 



418. The helmet (galea) is situated on the 

 back of the feeler-jaw, behind the blade, and 

 before the feeler; its variations are very nu- 

 merous, and, consequently, very useful in assign- 

 ing characters to insects. 



419. A palpiform helmet {galea palpiformis) 

 is when it is perfectly distinct from the blade, 

 and composed of one, two, three, or four cylin- 

 drical joints, like those of the feelers or 

 antennae : it has this form in carnivorous 

 beetles. 



420. An obtuse helmet (galea obtusa) is when 

 it appears simply as a shapeless mass ; it assumes 

 this form frequently when the lacinia is also 

 obtuse, and much resembles it in appearance. 



421. An obsolete helmet (galea obsoleta) is 

 when it is closely united to the blade : sometimes 

 a mere sutural line, and occasionally not even 

 that, denotes any separation between them. 



422. The maxillary feeler (maxipalpus) rises 

 from the feeler- bearer immediately behind the 

 helmet ; its principal variations are in the num- 

 .ber, form, and proportion of its joints : the 



description of these are very simple, and easily 

 understood, without the employment of any set 

 terms. 



423. The mandibles (mandibulce) are situated 



