THE RESTING HABIT OF INSECTS. 245 



with the larvse of Aplecta advena and A. tincta; the former, feeding on 

 low plants, reappear in March, the latter feeding on birch, in April. 

 The larVcB of (Jirrlioedia .vcrcunpcUna do not appear till May, when the 

 ash is budding /-■' The larvie of Boarmia repandata and Boaniua 

 rhuinholdaria feeding on blackthorn, bramble, plum, etc., are out early 

 on their food-plants ; whilst those of Boarmia wburariaf wait till 

 the oaks are in leaf in May. These are a few instances occurring 

 to me. 



Our ancestral larva, then, under severe climatic conditions, Avith a 

 short summer and long winter, would only have two courses open to it 

 when, not fully fed, it found its food-plant dying off and cold approach- 

 ing. It must either wander about in search of food, and, failing it, 

 incur death from starvation plus cold, or else it must meet the situa- 

 tion by suitable adaptation, i.e., by hyberuating. Does not the partial 

 wintering of so many of our late larvsfi help to corroborate this view ? 

 This state, during which the larvae nibble more or less on fine days 

 throughout the winter, seems not true hybernation, but rather 

 torpidity, and helps to illustrate the difference between the two condi- 

 tions. The larvae so acting, can of course only be such as are able 

 to find a food supply throughout the winter, i.e., those that feed on 

 grasses, plantain, roots, mosses, lichen, etc. They are exposed to 

 cold which they are able to resist as they can find food, and keep 

 themselves alive without true hybernation. Then, again, does not 

 our ability to force some hybernating larvae to pupate without hyber- 

 nation (so much carried on of late years) by means of constant food 

 supply plus high temperatures, point in the same direction '? Second 

 broods in the south, and even third partial broods in unusually hot 

 seasons, such as I recorded in 1893 {Ent. Becord, vol. iv., p. 344), 

 are other illustrations. Food and heat are the great obstacles to 

 hybernation — true it is, all larvae do not yield to these stimuli ; but, 

 then, is it not because their " ancestral memories " are too strong? 



The anomalous instances brought forward by Mr. Tutt, of insects 

 hybernating alike through the hottest and coldest weather, are 

 explicable on Mr. Kane's theory that they are unreasonable sur- 

 vivals. In some the hereditary tendency may be too strong, though 

 the environment may be altered and unsuitable the insects have not 

 yet adapted themselves to it, and still yield to the "memories" of 

 former times. 



The hybernation of the imago varies from that of the larva because 

 of the different part it has to play, and in its case cold certainly 

 seems the primary agent. The perfect insect, as a rule, has a short 

 existence ; its life object being the propagation of the species, and 

 after accomplishing its work as a reproductive agent, it dies. The 

 differences connected with its hybernation seem adapted to meet this 

 purpose. Most have emerged during the late autumn, and what they 

 have got to do is to keep alive long enough to pair and deposit eggs 

 in such a manner and at such a time as is most likely to ensure their 

 future development. This an insect may bring about in two ways, 

 either by covering them with suitable material, such as hairs, cement, 

 etc., as is done by some which lay eggs earlier in the season, which 



* March, on fiower-bucTs. — Eu. 



t Feed in .Yfarch and April on the rind of small twiys, and on buds till leaves 

 appear. — Ed. 



