THE BLACK BLISTER BEETLE. 75 



lated species, which resemble this one closely in size and 

 form, but which are variously striped. These afre all blister 

 beetles. 



Blistering Property. In collecting and studying them, 

 they should be handled with forceps and needles, and not 

 with the fingers ; for, when handled, there exudes from 

 the joints of the abdomen a yellowish fluid secretion con- 

 taining cantharidin, and possessing the power of blistering 

 the skin when coming in contact with it in sufficient 

 amount. This property is retained even when the insects 

 are dried, making them valuable to the apothecary. 



Collecting. A bottle is all the apparatus needed for 

 collecting this insect, an empty bottle for live speci- 

 mens, or a cyanide bottle for dead ones. They may be 

 pushed from the flowers or leaves directly into the bottle 

 with its stopper. 



Study the Live Insect. Observe the nature and extent 

 of its injury to the plants on which it feeds. Has it any 

 competitors for the food these plants supply ? 



Observe the action of its wings. Pick up with forceps 

 a live specimen by an antenna, and observe how it opens 

 and uses its wings. Put it down again, and observe how 

 it folds them up. 



Study specimens from the cyanide bottle. 



External Features. I. The Head. Observe that the 

 head is narrowed behind, to form a sort of neck at its 

 junction with the prothorax. 



Observe the size and position of eyes and ocelli. 



Examine an antenna, and study its structure and 

 action. Draw. 



Find in the mouth parts labrum, well-developed man- 

 dibles, maxilla3 with prominent palpi, and labium with 



