28 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 120 
range overlap between species, the stronger the interspecific differences 
in spermatophore morphology. For example in the jollae group, 
diandra, potentially in contact with both jollae and kolpos, has a 
surprisingly unique spermatophore, whereas the latter two are al- 
lopatric and show only weak differences in spermatophore morphology. 
Complexity and species-specificity in spermatophore morphology 
and constancy in its orientation with respect to the female urosome 
are compelling reasons to anticipate ritualistic mating behavior in the 
genus. Labidocera jollae has been observed briefly in copula on two 
occasions, once in January 1962 (pers. comm., Dr. Bui Thi Lang, SIO) 
and again in April 1964 (by the author). At first the two individuals 
were side by side. They quickly changed positions, pivoting about 
the region of the genital segment like the hands of a clock and causing 
the prosomes to be pointed in opposing directions while the urosomes 
crossed at about the level of the genital segments. Clasping lasted 
for at least 10 minutes. In both instances the observers were unable 
to note whether a spermatophore was deposited. More extensive 
observations on copepod mating behavior, however, are available for 
other genera. 
Hill and Coker (1930) provide considerable evidence of ritual asso- 
ciated with copulation as well as a critical time for spermatophore 
deposition derived from observations on mating in several species of 
freshwater cyclopoids. They found that, regardless of which female 
structure was initially grasped, the male would later shift its position 
until it had secured itself to the female’s fourth pair of swimming legs; 
furthermore, in several species, adult males remained close to or 
clasped alate stage V female and waited for ecdysis, thus guaranteeing 
that the spermatophore would be implanted on unhardened cuticle. 
Fahrenbach (1962) found a pronounced mating ritual in the algal- 
dwelling harpacticoid Diarthrodes cystoecus, while Gauld’s (1957) 
brief notes on mating in some estuarine-coastal planktonic calanoids 
(Centropages, Temora, Eurytemora, and Acartia) also suggest ritual 
prior to attachment of spermatophore and uniformity of orientation 
of the male during attachment. 
In Pseudodiaptomus euryhalinus and P. coronatus, copula persists 
for hours and even days, whereas in Acartia tonsa the act is apparently 
accomplished in less than a minute (Johnson, 1948; Jacobs, 1961). Jacobs 
(ibid., p. 445) observed that males were more prone to attack “when 
they chanced to become situated some 5 mm obliquely behind a female, 
leaving the impression that the attack might be triggered by the 
female feeding current.” Johnson (op. cit.) noted that when isolated 
Pseudodiaptomus males and females are brought together a high 
percentage of the animals may copulate within a few minutes. 
