the Biology of some British Neuroptera. 507 



in peritrophic membrane. In Coniopterygidae the excre- 

 ment is deposited in several black viscous masses. 



The adiiltwill not be described here, as its form is generally 

 well knoAvn, but the following point appears of interest. 

 On the lateral valves or paraprocts at the extremity of 

 the abdomen in both sexes is a pair of circular, dome- 

 shaped, unpigmented spots. These are covered with small 

 sensory hairs and are evidently of use in pairing, clearly 

 so in Osmylus. I consider that these spots are possibly 

 reduced cerci. 



The eggs in the ovaries of the female are at first not fully 

 developed, but mature in a few days. Animal food hastens 

 maturation more than does sugar. Sometimes insects will 

 not lay eggs if only supplied with sweet food, though the 

 latter will ahvays attract imagines, even from a distance. 



All the British forms are mainly crepuscular or nocturnal 

 in habits and are attracted to light. 



Winter may be passed in any stage, with the apparent 

 exception of the egg, but ? Boriomyia concinna. 



The length of life of a male imago is generally only a few 

 weeks ; of a female, up to three months. 



Internal Anatomy. 



Larva (Plate XXXIX, fig. 5).— The mouth is closed at first 

 by membrane, as described in the account of the hatching 

 larva ; later, the mouth opening appears to be closed by close 

 application of roof and floor, the one being moulded to fit 

 the other by ridge and groove. The channels from each 

 jaw unite in a Y-shaped joint, and then the common 

 channel (pharynx) takes an oblique course dorsalwards. 

 The oblique part of the channel has its walls a little more 

 strongly chitinised than the rest of the pharynx, and attached 

 before and behind are muscles, which by their contraction 

 serve to widen the lumen. Thus we have a pharyngeal 

 pump formed, supplying the necessary suction for feeding. 

 Now the alimentary canal once more runs horizontally. 

 The oesophagus dilates behind into a crop. After a slight 

 constriction the gut continues as mesenteron or stomach, 

 which normally would not be lined v/ith chitin, but from the 

 hind part of the oesophagus there is secreted a delicate 

 chitinous cylinder, the peritrophic membrane, which hangs 

 free the entire length of the stomach and thus protects the 

 gastric epithelium from actual contact with the stomach 



