3128 



THE JOINTED ANIMALS 



with three-jointed palpi. The antenna are setiform, and inserted between the 

 rather prominent eyes, and below the ocelli, which are usually distinct. The pro- 

 thorax is short and collar-like; and the wings of these insects are less closely reticu- 

 lated, and have fewer transverse nervures than those of the other groups. The 

 common scorpion fly (Ponorpa communis}, which may be taken as the type of the 



COMMON SCORPION FLY. 

 a. Female depositing her eggs ; b. Male ; c. Larva ; d. Pupa. 



family, is a shiny black insect about half an inch or more in length, with long, 

 transparent, spotted wings, and a yellow beak and legs. The last three body 

 segments of the male are narrow, and can be curved like a tail, and have a reddish 

 color; the last carries a pair of pincer-like claws. It is from this circumstance 

 that the insect has received its name, though it does not possess a sting like a 



scorpion. 



In the snake flies and alder flies (Sta- 

 lidce}, forming the second family, the 

 head is comparatively large, and often in- 

 clined in front, but never elongated in the 

 form of a beak. The antennas are bristle- 

 like, and not so long as the body; the pro- 

 thorax being strongly developed. The 

 camel or snake flies (Rhaphidia] have the 

 head long and narrow behind, and freely 

 articulated with the long and narrow pro- 

 thorax. The latter can also move freely at 

 its articulation with the segment which fol- 

 lows; and this explains how the prothorax 

 is raised, and the head bent forward in the 

 characteristic attitude which these insects 

 adopt when about to seize their prey, which 

 consists usually of various small insects. 



The alder fly, or May fly (Sialis lutaria) , 

 is at first sight rather like a caddice fly, but 

 has a stouter body, and may be distin- 

 guished by its more completely developed 

 mouth organs, as well as by the different 



HISTORY OF THE ALDER FLY. structure of its wings. It emerges from the 

 i. Eggs; 2. Larva; 3 . Pupa; 4. imago. pupa about May or June. The winged in- 



