THE HIDDEN TYPE OF WING-GROWTH 101 



bearing tubercle and the galea is represented by two short 

 cylindrical segments ; the base (stipes) and the palp are 

 prominent. In the labium (Fig. 55 d) can be distinguished the 

 base (mentum), the median ligula and the pair of short, two- 

 segmented palps. In some ground-beetle larvae a pair of 

 lobes representing the maxillulae can be detected. The thorax 

 has its three segments with cuticle thick and firm ; the three 

 pairs of legs (Fig. 55 e) are closely alike in structure, each being 

 composed of haunch, trochanter, thigh, shin and foot, the 

 last-named consisting of a single piece only, bearing two claws 

 at its tip. Each of the nine evident abdominal segments has 

 a strongly chitinized dorsal plate (tergum), a lateral sclerite 

 on either side, and several ventral sclerites with intervening 

 tracts of comparatively thin and flexible cuticle. The ninth 

 segment bears a pair of stiff, bristly cerci, and between these 

 the tubular tail-segment with the intestinal opening (anus) at 

 its tip, projects backwards and downwards. As this tail- 

 segment is used by the larva in locomotion to support the 

 hinder region of the body it is often spoken of as an " anal 

 proleg ". Spiracles paired openings leading to the air-tube 

 system are present on the prothorax and on the abdominal 

 segments from the first to the eighth inclusive. They are 

 absent as in the caterpillar (see p. 58) from the second and 

 third thoracic segments to which the wings belong. 



Such a ground-beetle larva lives lurking under stones or 

 just beneath the surface of the soil, sallying forth, usually in 

 the dark, to hunt for the smaller or weaker insects that serve 

 as its prey. Among beetles of other families modifications of 

 this campodeiform type of larva may be found. The aquatic 

 larva of the large carnivorous water-beetle (Dyticus) shows this 

 type adapted for life under water and for feeding by suction. 

 It has a large head with long feelers and maxillary palps ; the 

 mandibles are slender, sharply pointed and strongly curved, each 

 with a narrow tubular channel running from tip to base where 

 it opens at the corner of the mouth. The Dyticus grub digs 

 these formidable weapons into the body of its victim a small 

 fish, a tadpole, or a weak insect and is thus able to suck 

 blood or other juices of its prey as food. The body is very 

 well armoured, the sternal plates, as well as the tergal, being 

 extensive ; the legs are long, and each foot, as in the ground- 



