70 EN TOMOLOGY 
Hairs, Setz and Spines.—These occur universally, serv- 
eee ing a great variety of purposes; they 
are not always simple in form, but are 
often toothed, branched or otherwise 
modified (Fig. 89). Hairs and bris- 
tles are frequently tactile in function, 
over the general integument or else 
locally ; or olfactory, as on the antennz 
of moths; or occasionally auditory, as 
on the antenne of the male mosquito; 
these and other sensory modifications 
are described beyond. The hairy 
clething of some hibernating cater- 
pillars (as sia isabella) probably pro- 
Section of antenna of a Z 7 
moth, Saturnia, to show tects them from sudden changes ot 
developing hairs. c, cutic- 
temperature. Hairs and spines. fre- 
ula; f, formative cell of : ; 
hair; h, hypodermis;  ¢, quently protect an insect trom its ene- 
trachea.—After SEMPER. : ; : ; 
mies, especially when these structures 
are glandular and emit a 
= TG s7O Ire 
malodorous, nauseous or a 
irritant fluid. Glandular 
hairs on the pulvilli of 
Mmamy ‘ties; -beetles,s .ete:, 
enable these insects to walk 
on slippery surfaces. The 
twisted or branched hairs 
of bees serve to gather 
and hold pollen grains; in 
short, these simple struc- 
tures exhibit a surprising 
variety of adaptive modifica- 
tions, many of which will be 
Radial section through the base of a 
described im connection with hair of a caterpillar, Pieris rape. c, cutic- 
other subjects. ula; f, formative cell; h, hair; hy, hypo- 
dermis. 
A hair arises from a 
modified hypodermis cell (Fig. 90), the contents of which 
