262 ENTOMOLOGY FOR MEDICAL OFFICERS 



Order Mecoptera : Scorpion-flies. 

 (Gr. /x^/co? = length, and •7rTe/)oV= wing.) 



A small order of insects, consisting of one small family — 

 Panorpidcs — closely related to the Neuroptera. 



The head is produced downwards into a long, stout beak, 

 which bears the mandibles at its tip. The antennae are long 

 and slender. There are usually two pairs of long, rather 

 narrow, membranous wings, which have numerous long veins 

 but only a moderate number of cross-veins ; some species are 

 wingless. In the males of Panorpa the terminal segments of 

 the abdomen are narrowed and are carried aloft aggressively 

 like the "tail" of the scorpion. The larva has ordinary 

 biting mouth-parts, true segmented legs on the thoracic 

 segments, and stumpy legs (pseudopods) on most of the 

 abdominal segments. Both adult and larva are carnivorous. 



Order Trichoptera: Caddis-flies. 

 (Gr. Qpi^, T/OixoV = hair, and 7rTe/)6V = wing.) 



Moth-like insects, very closely related to Moths (Lepidop- 

 terd), found near water. There are two pairs of wings, which 

 are covered with fine hair, the hind pair being the larger. 

 The mouth-parts have the form of a short sucking-tube which 

 is formed by the labrum, labium, and maxillae ; the maxillary 

 and labial palps are conspicuous. The antennae are thread- 

 like and are sometimes very long. 



The larvae, known as caddis-worms, are aquatic, and 

 commonly live in portable tubes of their own construction : 

 these are made of all sorts of stuff, cemented together by 

 silky threads — usually of bits of grass, or stick, and dead leaf, 

 sometimes of small stones, shells, or grains of sand ; they are 

 generally open at both ends, so that currents of water for 

 breathing may pass through, breathing being usually carried 

 on by lateral abdominal gill-filaments. Caddis-worms are 

 found in water of all kinds : most of them are herbivorous, 

 but some of those that live in rapid streams are carnivorous ; 

 these last construct fixed retreats and spin webs for snaring 

 their prey, which may consist among other things, of the 

 larvae of Siniuliuin. 



