PiM. 1. Vin.1913. -COSSIDAE. By Dr. A. Seitz. 417 



25. Family: Cossidae. 



The „wood-borers" are a faiiiy natural group of moths, about whose various species on the whole very 

 little is known. The family has no very obvious affinities with any of the Bombycids, and the characters which 

 they have in common with the Hepialids, near which family ths Cossidae are generally placed, prove at first 

 glance to be mere secondary adaptations, which are no evidence of blood-relationship between the two families. 

 Altogether more than two hundred species are known, which are fairly evenly distributed, one group (Mye- 

 lohius), although containing gigantic forms, having been proved to be hardly separable from the Pyralids. 

 But even the true Cossids appear to be closely related to the Microlepidoptera, viz. to the Tortricidae, although 

 they may not be directly derived from them. Conspicuous characters are: first, the totally obsolete mouth- 

 parts, the reduction sometimes leading almost to the disappearance of the tongue and palpi ; secondly, very 

 primitive venation, this being so regular that scarcely any part of the wing remains unsupported, even the 

 inner-marginal vein of the forewing and an unusually strong intracellular vein being forked again ; and, thirdly 

 that m most genera that portion of the forewing which bears most of the pressure during flight is strengthened 

 by the subcostal veins anastomosing. The frequent anastomosis of vems renders the wings remarkably stiff 

 and hard, so that a specimen of Cossus emerging need not, like most Lepidoptera, bring its wings into a hanging- 

 down position for development, but, resting on the horizontal ground, it holds its wings upright, in which 

 position they expand completely, as observed by Frings in Cossus cossus. The rather long thorax is also 

 very primitive, its thnd segment not being closely fused with the mesothorax, so that the bases of forewing 

 and hindwing are rather far apart, and the wings would easily be dislocated if they were not supported, beside 

 the very strong frenulum, by an uiner-marginal lobe of the forewing and often a costal lobe of the hmdwing, 

 which lobes help to keep the wings in their natural position. This arrangement reminds us of the connection 

 of the wings in Hepialids which originate so far apart that a whole network of supporting and cross-veins 

 is needed at the hind margm of the forewing and the costal margin of the hindwing to prevent the hindwing 

 from slipping over the forewmg, a danger of which one becomes aware when setting Hepialidae. 



The head is only moderately large and m the (JcJ also consists almost entirely of the very large eyes, 

 which closely approach each other on the underside of the head even though they do not exclusively form 

 the head, as e. g. in the Hepialid genus Oenetus, where they almost touch, as in dragon-flies, only leaving 

 a very narrow interspace. The antennae are very variable, being strongly developed in some Australian species, 

 and in certain Zeuzera almost as much reduced as those of the Hepialidae. Tongue always atrophied, being 

 at most a short thread quite useless for the purpose of taking food, but the palpi are very variously developed, 

 bemg quite different in evidently closely allied species and of just as little taxonomic value in this group as 

 the antennae. The body is always strong in comparison with the stiff hard wings, sometimes scarcely larger 

 than that of a Psychid, sometimes of gigantic proportions. Thorax very stout, with a hard shell, mesothorax 

 with short hair, prothorax and metathorax usually with longer and often tufted hair. Legs of medium length, 

 very strong, with reduced tibial spurs, but sharp, large tarsal claws. — Larvae smooth, glossy, with minute 

 warts and strong short bristles, flat head, strong mandibles, rings of hooks on the abdominal .legs and remark- 

 ably strong muscles. The contraction of several thousand bundles of transversely striped fibres of muscles 

 (which someone has taken the pains of counting in Cossus cossus) enable the larva to use great strength, which 

 is a necessity for a larva feedmg inside wood. They can pinch severely with their mandibles, and also defend 

 themselves by squirting out an acrid liquid from a slit below the head. They bore enormous tunnels in the 

 wood, and the very coarse frass becomes rotten, resembling wood-mould, and often has a characteristic odour 

 which betrays the larva to the collector. The pupa has only loosely connected limb-sheaths, and bears strong 

 rmgs of hooks on the abdomen, with which it pushes its way out of the cocoon. The moths usually fly very 

 late at night and many are strongly attracted by light. The development of the larger species takes two years. All 

 the moths become greasy so easily that it is advisable to empty the abdomen and to stuff it with cotton-wool. 

 Moreover, black insect-pins should always be used, as otherwise verdigris develops to such an extent as to 

 burst the thorax. 



New Cossids are described nearly every year, so that the number of species is sure to increase consi- 

 derably still, and even in the Palearctic Region we cannot regard the list as complete. Many species are rare; 

 really common are only the ^eMzera, especinWy Zeuzera py7-in a, large numbers of M'hich often flutter around the 

 lamps in America and Africa, and the very similar coffee-borer, Z. coffeae, which often does great damage 

 in plantations. The species known up to the present are so distributed that the Palearctic and American Regions 

 contain each about 50 to 60; the Indo-Australian region has rather more, forms, and Africa as yet slightly 

 fewer, but this will probably be altered when larger collections of Heterocera come from Africa. 



II 53 



